* [PATCH 03/12] timer_list: Print offset as signed integer
From: Thomas Weißschuh (Schneider Electric) @ 2026-03-11 10:15 UTC (permalink / raw)
To: Jan Kiszka, Kieran Bingham, John Stultz, Thomas Gleixner,
Anna-Maria Behnsen, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Frederic Weisbecker, Stephen Boyd
Cc: linux-kernel, linux-trace-kernel,
Thomas Weißschuh (Schneider Electric)
In-Reply-To: <20260311-hrtimer-cleanups-v1-0-095357392669@linutronix.de>
The offset of a hrtimer base may be negative.
Print those values correctly.
Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
---
kernel/time/timer_list.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
index e2e14fd1b466..427d7ddea3af 100644
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -101,8 +101,8 @@ print_base(struct seq_file *m, struct hrtimer_clock_base *base, u64 now)
SEQ_printf(m, " .resolution: %u nsecs\n", hrtimer_resolution);
#ifdef CONFIG_HIGH_RES_TIMERS
- SEQ_printf(m, " .offset: %Lu nsecs\n",
- (unsigned long long) ktime_to_ns(base->offset));
+ SEQ_printf(m, " .offset: %Ld nsecs\n",
+ (long long) base->offset);
#endif
SEQ_printf(m, "active timers:\n");
print_active_timers(m, base, now + ktime_to_ns(base->offset));
--
2.53.0
^ permalink raw reply related
* [PATCH 04/12] timekeeping: auxclock: Consistently use raw timekeeper for tk_setup_internals()
From: Thomas Weißschuh (Schneider Electric) @ 2026-03-11 10:15 UTC (permalink / raw)
To: Jan Kiszka, Kieran Bingham, John Stultz, Thomas Gleixner,
Anna-Maria Behnsen, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Frederic Weisbecker, Stephen Boyd
Cc: linux-kernel, linux-trace-kernel,
Thomas Weißschuh (Schneider Electric)
In-Reply-To: <20260311-hrtimer-cleanups-v1-0-095357392669@linutronix.de>
In aux_clock_enable() the clocksource from tkr_raw is used to call
tk_setup_internals(). Do the same in tk_aux_update_clocksource().
While the clocksources will be the same in any case, this is less
confusing.
Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
---
kernel/time/timekeeping.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 5153218df29f..46b77c3deb95 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -2985,7 +2985,7 @@ static void tk_aux_update_clocksource(void)
continue;
timekeeping_forward_now(tks);
- tk_setup_internals(tks, tk_core.timekeeper.tkr_mono.clock);
+ tk_setup_internals(tks, tk_core.timekeeper.tkr_raw.clock);
timekeeping_update_from_shadow(tkd, TK_UPDATE_ALL);
}
}
--
2.53.0
^ permalink raw reply related
* [PATCH 05/12] timekeeping: Mark offsets array as const
From: Thomas Weißschuh (Schneider Electric) @ 2026-03-11 10:15 UTC (permalink / raw)
To: Jan Kiszka, Kieran Bingham, John Stultz, Thomas Gleixner,
Anna-Maria Behnsen, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Frederic Weisbecker, Stephen Boyd
Cc: linux-kernel, linux-trace-kernel,
Thomas Weißschuh (Schneider Electric)
In-Reply-To: <20260311-hrtimer-cleanups-v1-0-095357392669@linutronix.de>
Neither the array nor the offsets it is pointing to are meant to be
changed through the array.
Mark both the array and the values it points to as const.
Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
---
kernel/time/timekeeping.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 46b77c3deb95..27f17428f7c5 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -989,7 +989,7 @@ u32 ktime_get_resolution_ns(void)
}
EXPORT_SYMBOL_GPL(ktime_get_resolution_ns);
-static ktime_t *offsets[TK_OFFS_MAX] = {
+static const ktime_t *const offsets[TK_OFFS_MAX] = {
[TK_OFFS_REAL] = &tk_core.timekeeper.offs_real,
[TK_OFFS_BOOT] = &tk_core.timekeeper.offs_boot,
[TK_OFFS_TAI] = &tk_core.timekeeper.offs_tai,
@@ -998,8 +998,9 @@ static ktime_t *offsets[TK_OFFS_MAX] = {
ktime_t ktime_get_with_offset(enum tk_offsets offs)
{
struct timekeeper *tk = &tk_core.timekeeper;
+ const ktime_t *offset = offsets[offs];
unsigned int seq;
- ktime_t base, *offset = offsets[offs];
+ ktime_t base;
u64 nsecs;
WARN_ON(timekeeping_suspended);
@@ -1019,8 +1020,9 @@ EXPORT_SYMBOL_GPL(ktime_get_with_offset);
ktime_t ktime_get_coarse_with_offset(enum tk_offsets offs)
{
struct timekeeper *tk = &tk_core.timekeeper;
- ktime_t base, *offset = offsets[offs];
+ const ktime_t *offset = offsets[offs];
unsigned int seq;
+ ktime_t base;
u64 nsecs;
WARN_ON(timekeeping_suspended);
@@ -1043,7 +1045,7 @@ EXPORT_SYMBOL_GPL(ktime_get_coarse_with_offset);
*/
ktime_t ktime_mono_to_any(ktime_t tmono, enum tk_offsets offs)
{
- ktime_t *offset = offsets[offs];
+ const ktime_t *offset = offsets[offs];
unsigned int seq;
ktime_t tconv;
--
2.53.0
^ permalink raw reply related
* [PATCH 06/12] hrtimer: Remove hrtimer_get_expires_ns()
From: Thomas Weißschuh (Schneider Electric) @ 2026-03-11 10:15 UTC (permalink / raw)
To: Jan Kiszka, Kieran Bingham, John Stultz, Thomas Gleixner,
Anna-Maria Behnsen, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Frederic Weisbecker, Stephen Boyd
Cc: linux-kernel, linux-trace-kernel,
Thomas Weißschuh (Schneider Electric)
In-Reply-To: <20260311-hrtimer-cleanups-v1-0-095357392669@linutronix.de>
There are no users left.
Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
---
include/linux/hrtimer.h | 5 -----
1 file changed, 5 deletions(-)
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index c087b7142330..9ced498fefaa 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -116,11 +116,6 @@ static inline ktime_t hrtimer_get_softexpires(const struct hrtimer *timer)
return timer->_softexpires;
}
-static inline s64 hrtimer_get_expires_ns(const struct hrtimer *timer)
-{
- return ktime_to_ns(timer->node.expires);
-}
-
ktime_t hrtimer_cb_get_time(const struct hrtimer *timer);
static inline ktime_t hrtimer_expires_remaining(const struct hrtimer *timer)
--
2.53.0
^ permalink raw reply related
* [PATCH 07/12] hrtimer: Don't zero-initialize ret in hrtimer_nanosleep()
From: Thomas Weißschuh (Schneider Electric) @ 2026-03-11 10:15 UTC (permalink / raw)
To: Jan Kiszka, Kieran Bingham, John Stultz, Thomas Gleixner,
Anna-Maria Behnsen, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Frederic Weisbecker, Stephen Boyd
Cc: linux-kernel, linux-trace-kernel,
Thomas Weißschuh (Schneider Electric)
In-Reply-To: <20260311-hrtimer-cleanups-v1-0-095357392669@linutronix.de>
The value will be assigned to before any usage.
No other function in hrtimer.c does such a zero-initialization.
Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
---
kernel/time/hrtimer.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index b94bd56b739f..226cac8c82cc 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -2328,7 +2328,7 @@ long hrtimer_nanosleep(ktime_t rqtp, const enum hrtimer_mode mode, const clockid
{
struct restart_block *restart;
struct hrtimer_sleeper t;
- int ret = 0;
+ int ret;
hrtimer_setup_sleeper_on_stack(&t, clockid, mode);
hrtimer_set_expires_range_ns(&t.timer, rqtp, current->timer_slack_ns);
--
2.53.0
^ permalink raw reply related
* [PATCH 08/12] hrtimer: Drop spurious space in 'enum hrtimer_base_type'
From: Thomas Weißschuh (Schneider Electric) @ 2026-03-11 10:15 UTC (permalink / raw)
To: Jan Kiszka, Kieran Bingham, John Stultz, Thomas Gleixner,
Anna-Maria Behnsen, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Frederic Weisbecker, Stephen Boyd
Cc: linux-kernel, linux-trace-kernel,
Thomas Weißschuh (Schneider Electric)
In-Reply-To: <20260311-hrtimer-cleanups-v1-0-095357392669@linutronix.de>
This spurious space makes grepping for the enum definition annoying.
Remove it.
Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
---
include/linux/hrtimer_defs.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/hrtimer_defs.h b/include/linux/hrtimer_defs.h
index 0f851b2432c3..e6d4dc1b61e0 100644
--- a/include/linux/hrtimer_defs.h
+++ b/include/linux/hrtimer_defs.h
@@ -35,7 +35,7 @@ struct hrtimer_clock_base {
ktime_t offset;
} __hrtimer_clock_base_align;
-enum hrtimer_base_type {
+enum hrtimer_base_type {
HRTIMER_BASE_MONOTONIC,
HRTIMER_BASE_REALTIME,
HRTIMER_BASE_BOOTTIME,
--
2.53.0
^ permalink raw reply related
* [PATCH 09/12] hrtimer: Drop unnecessary pointer indirection in hrtimer_expire_entry event
From: Thomas Weißschuh (Schneider Electric) @ 2026-03-11 10:15 UTC (permalink / raw)
To: Jan Kiszka, Kieran Bingham, John Stultz, Thomas Gleixner,
Anna-Maria Behnsen, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Frederic Weisbecker, Stephen Boyd
Cc: linux-kernel, linux-trace-kernel,
Thomas Weißschuh (Schneider Electric)
In-Reply-To: <20260311-hrtimer-cleanups-v1-0-095357392669@linutronix.de>
This pointer indirection is a remnant from when ktime_t was a struct,
today it is pointless.
Drop the pointer indirection.
Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
---
include/trace/events/timer.h | 7 +++----
kernel/time/hrtimer.c | 4 ++--
2 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index a54613f59e55..07cbb9836b91 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -254,14 +254,13 @@ TRACE_EVENT(hrtimer_start,
/**
* hrtimer_expire_entry - called immediately before the hrtimer callback
* @hrtimer: pointer to struct hrtimer
- * @now: pointer to variable which contains current time of the
- * timers base.
+ * @now: variable which contains current time of the timers base.
*
* Allows to determine the timer latency.
*/
TRACE_EVENT(hrtimer_expire_entry,
- TP_PROTO(struct hrtimer *hrtimer, ktime_t *now),
+ TP_PROTO(struct hrtimer *hrtimer, ktime_t now),
TP_ARGS(hrtimer, now),
@@ -273,7 +272,7 @@ TRACE_EVENT(hrtimer_expire_entry,
TP_fast_assign(
__entry->hrtimer = hrtimer;
- __entry->now = *now;
+ __entry->now = now;
__entry->function = ACCESS_PRIVATE(hrtimer, function);
),
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 226cac8c82cc..d350bceb3c95 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1884,7 +1884,7 @@ EXPORT_SYMBOL_GPL(hrtimer_active);
* __run_hrtimer() invocations.
*/
static void __run_hrtimer(struct hrtimer_cpu_base *cpu_base, struct hrtimer_clock_base *base,
- struct hrtimer *timer, ktime_t *now, unsigned long flags)
+ struct hrtimer *timer, ktime_t now, unsigned long flags)
__must_hold(&cpu_base->lock)
{
enum hrtimer_restart (*fn)(struct hrtimer *);
@@ -1989,7 +1989,7 @@ static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now,
if (basenow < hrtimer_get_softexpires(timer))
break;
- __run_hrtimer(cpu_base, base, timer, &basenow, flags);
+ __run_hrtimer(cpu_base, base, timer, basenow, flags);
if (active_mask == HRTIMER_ACTIVE_SOFT)
hrtimer_sync_wait_running(cpu_base, flags);
}
--
2.53.0
^ permalink raw reply related
* [PATCH 10/12] hrtimer: Mark index and clockid of clock base as const
From: Thomas Weißschuh (Schneider Electric) @ 2026-03-11 10:15 UTC (permalink / raw)
To: Jan Kiszka, Kieran Bingham, John Stultz, Thomas Gleixner,
Anna-Maria Behnsen, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Frederic Weisbecker, Stephen Boyd
Cc: linux-kernel, linux-trace-kernel,
Thomas Weißschuh (Schneider Electric)
In-Reply-To: <20260311-hrtimer-cleanups-v1-0-095357392669@linutronix.de>
These fields are initialized once and are never supposed to change.
Mark them as const to make this explicit.
Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
---
include/linux/hrtimer_defs.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/hrtimer_defs.h b/include/linux/hrtimer_defs.h
index e6d4dc1b61e0..a03240c0b14f 100644
--- a/include/linux/hrtimer_defs.h
+++ b/include/linux/hrtimer_defs.h
@@ -26,8 +26,8 @@
*/
struct hrtimer_clock_base {
struct hrtimer_cpu_base *cpu_base;
- unsigned int index;
- clockid_t clockid;
+ const unsigned int index;
+ const clockid_t clockid;
seqcount_raw_spinlock_t seq;
ktime_t expires_next;
struct hrtimer *running;
--
2.53.0
^ permalink raw reply related
* [PATCH 11/12] hrtimer: Remove trailing comma after HRTIMER_MAX_CLOCK_BASES
From: Thomas Weißschuh (Schneider Electric) @ 2026-03-11 10:15 UTC (permalink / raw)
To: Jan Kiszka, Kieran Bingham, John Stultz, Thomas Gleixner,
Anna-Maria Behnsen, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Frederic Weisbecker, Stephen Boyd
Cc: linux-kernel, linux-trace-kernel,
Thomas Weißschuh (Schneider Electric)
In-Reply-To: <20260311-hrtimer-cleanups-v1-0-095357392669@linutronix.de>
HRTIMER_MAX_CLOCK_BASES is required to stay the last value of the enum.
Drop the trailing comma so no new members are added after it by mistake.
Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
---
include/linux/hrtimer_defs.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/hrtimer_defs.h b/include/linux/hrtimer_defs.h
index a03240c0b14f..52ed9e46ff13 100644
--- a/include/linux/hrtimer_defs.h
+++ b/include/linux/hrtimer_defs.h
@@ -44,7 +44,7 @@ enum hrtimer_base_type {
HRTIMER_BASE_REALTIME_SOFT,
HRTIMER_BASE_BOOTTIME_SOFT,
HRTIMER_BASE_TAI_SOFT,
- HRTIMER_MAX_CLOCK_BASES,
+ HRTIMER_MAX_CLOCK_BASES
};
/**
--
2.53.0
^ permalink raw reply related
* [PATCH 12/12] hrtimer: Add a helper to retrieve a hrtimer from its timerqueue node
From: Thomas Weißschuh (Schneider Electric) @ 2026-03-11 10:15 UTC (permalink / raw)
To: Jan Kiszka, Kieran Bingham, John Stultz, Thomas Gleixner,
Anna-Maria Behnsen, Steven Rostedt, Masami Hiramatsu,
Mathieu Desnoyers, Frederic Weisbecker, Stephen Boyd
Cc: linux-kernel, linux-trace-kernel,
Thomas Weißschuh (Schneider Electric)
In-Reply-To: <20260311-hrtimer-cleanups-v1-0-095357392669@linutronix.de>
The container_of() call is open-coded multiple times.
Add a helper macro.
Use container_of_const() to preserve constness.
Signed-off-by: Thomas Weißschuh (Schneider Electric) <thomas.weissschuh@linutronix.de>
---
kernel/time/hrtimer.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index d350bceb3c95..94955f967207 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -534,6 +534,8 @@ static inline void debug_activate(struct hrtimer *timer, enum hrtimer_mode mode,
for (bool done = false; !done; active &= ~(1U << idx)) \
for (base = &cpu_base->clock_base[idx]; !done; done = true)
+#define hrtimer_from_timerqueue_node(_n) container_of_const(_n, struct hrtimer, node)
+
#if defined(CONFIG_NO_HZ_COMMON)
/*
* Same as hrtimer_bases_next_event() below, but skips the excluded timer and
@@ -578,7 +580,7 @@ static __always_inline struct hrtimer *clock_base_next_timer(struct hrtimer_cloc
{
struct timerqueue_linked_node *next = timerqueue_linked_first(&base->active);
- return container_of(next, struct hrtimer, node);
+ return hrtimer_from_timerqueue_node(next);
}
/* Find the base with the earliest expiry */
@@ -1960,7 +1962,7 @@ static __always_inline struct hrtimer *clock_base_next_timer_safe(struct hrtimer
{
struct timerqueue_linked_node *next = timerqueue_linked_first(&base->active);
- return next ? container_of(next, struct hrtimer, node) : NULL;
+ return next ? hrtimer_from_timerqueue_node(next) : NULL;
}
static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now,
@@ -2438,7 +2440,7 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
struct hrtimer *timer;
while ((node = timerqueue_linked_first(&old_base->active))) {
- timer = container_of(node, struct hrtimer, node);
+ timer = hrtimer_from_timerqueue_node(node);
BUG_ON(hrtimer_callback_running(timer));
debug_hrtimer_deactivate(timer);
--
2.53.0
^ permalink raw reply related
* Re: [PATCH v2 1/2] kthread: remove kthread_exit()
From: David Laight @ 2026-03-11 10:47 UTC (permalink / raw)
To: Christian Brauner
Cc: Linus Torvalds, linux-kernel, linux-modules, linux-nfs, bpf,
kunit-dev, linux-doc, linux-trace-kernel, netfs, io-uring, audit,
rcu, kvm, virtualization, netdev, linux-mm, linux-security-module,
Christian Loehle, linux-fsdevel
In-Reply-To: <20260310-work-kernel-exit-v2-1-30711759d87b@kernel.org>
On Tue, 10 Mar 2026 15:56:09 +0100
Christian Brauner <brauner@kernel.org> wrote:
> In 28aaa9c39945 ("kthread: consolidate kthread exit paths to prevent use-after-free")
> we folded kthread_exit() into do_exit() when we fixed a nasty UAF bug.
> We left kthread_exit() around as an alias to do_exit(). Remove it
> completely.
...
> -#define module_put_and_kthread_exit(code) kthread_exit(code)
> +#define module_put_and_kthread_exit(code) do_exit(code)
I'm intrigued...
How does that actually know to do the module_put()?
(I know it does one - otherwise my driver wouldn't unload.)
The corresponding try_module_get(THIS_MODULE) is done before the
kthread_run() (and has to be 'put' if that fails).
So there is an explicit 'get' but an implicit 'put'.
While a loadable module that creates a kthread usually needs to give
the kthread a reference to its module and then have that reference
released as the kthread exits, I can imagine cases where that isn't true.
(Or broken code that just hopes the module won't be unloaded just
as the kthread exits.)
It actually makes me think that module_put_and_exit() ought to have
a 'module' parameter.
Or, perhaps, kthread_create() should have the module parameter and
hold a reference to that module until it exits.
David
^ permalink raw reply
* Re: [PATCH v2 1/3] tracing: Have futex syscall trace event show specific user data
From: kernel test robot @ 2026-03-11 11:23 UTC (permalink / raw)
To: Steven Rostedt, linux-kernel, linux-trace-kernel
Cc: oe-kbuild-all, Masami Hiramatsu, Mark Rutland, Mathieu Desnoyers,
Andrew Morton, Linux Memory Management List, Thomas Gleixner,
Brian Geffon, John Stultz, Ian Rogers, Suleiman Souhlal
In-Reply-To: <20260310201036.542627924@kernel.org>
Hi Steven,
kernel test robot noticed the following build warnings:
[auto build test WARNING on tip/locking/core]
[also build test WARNING on trace/for-next akpm-mm/mm-everything linus/master v7.0-rc3 next-20260310]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Steven-Rostedt/tracing-Have-futex-syscall-trace-event-show-specific-user-data/20260311-041422
base: tip/locking/core
patch link: https://lore.kernel.org/r/20260310201036.542627924%40kernel.org
patch subject: [PATCH v2 1/3] tracing: Have futex syscall trace event show specific user data
config: arc-randconfig-001-20260311 (https://download.01.org/0day-ci/archive/20260311/202603111911.zAWpiGlz-lkp@intel.com/config)
compiler: arc-linux-gcc (GCC) 14.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260311/202603111911.zAWpiGlz-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603111911.zAWpiGlz-lkp@intel.com/
All warnings (new ones prefixed by >>):
kernel/trace/trace_syscalls.c: In function 'syscall_get_futex':
>> kernel/trace/trace_syscalls.c:807:15: warning: variable 'buf' set but not used [-Wunused-but-set-variable]
807 | char *buf;
| ^~~
vim +/buf +807 kernel/trace/trace_syscalls.c
801
802 static int
803 syscall_get_futex(unsigned long *args, char **buffer, int *size, int buf_size)
804 {
805 struct syscall_user_buffer *sbuf;
806 const char __user *ptr;
> 807 char *buf;
808
809 /* buf_size of zero means user doesn't want user space read */
810 if (!buf_size)
811 return -1;
812
813 /* If the syscall_buffer is NULL, tracing is being shutdown */
814 sbuf = READ_ONCE(syscall_buffer);
815 if (!sbuf)
816 return -1;
817
818 ptr = (char __user *)args[0];
819
820 *buffer = trace_user_fault_read(&sbuf->buf, ptr, 4, NULL, NULL);
821 if (!*buffer)
822 return -1;
823
824 /* Add room for the value */
825 *size += 4;
826
827 buf = *buffer;
828
829 return 0;
830 }
831
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply
* [RFC PATCH v2 0/3] disable optimistic spinning for ftrace_lock
From: Yafang Shao @ 2026-03-11 11:52 UTC (permalink / raw)
To: peterz, mingo, will, boqun, longman, rostedt, mhiramat,
mark.rutland, mathieu.desnoyers, david.laight.linux
Cc: linux-kernel, linux-trace-kernel, Yafang Shao
Recently, we resolved a latency spike issue caused by concurrently running
bpftrace processes. The root cause was high contention on the ftrace_lock
due to optimistic spinning. We can optimize this by disabling optimistic
spinning for ftrace_lock.
While semaphores may present similar challenges, I'm not currently aware of
specific instances that exhibit this exact issue. Should we encounter
problematic semaphores in production workloads, we can address them at that
time.
PATCH #1: introduce slow_mutex_[un]lock to disable optimistic spinning
PATCH #2: add variant for rtmutex
PATCH #3: disable optimistic spinning for ftrace_lock
v1->v2:
- add slow_mutex_[un]lock (Steven)
- add variant for rtmutex (Waiman)
- revise commit log for clarity and accuracy (Waiman, Peter)
- note that semaphores may present similar challenges (David)
RFC v1: https://lore.kernel.org/bpf/20260304074650.58165-1-laoar.shao@gmail.com/
Yafang Shao (3):
locking/mutex: Add slow path variants for lock/unlock
locking/rtmutex: Add slow path variants for lock/unlock
ftrace: Disable optimistic spinning for ftrace_lock
include/linux/mutex.h | 4 ++
include/linux/rtmutex.h | 3 +
kernel/locking/mutex.c | 41 +++++++++++---
kernel/locking/rtmutex.c | 37 +++++++-----
kernel/locking/rtmutex_api.c | 47 +++++++++++++---
kernel/trace/ftrace.c | 106 +++++++++++++++++------------------
6 files changed, 157 insertions(+), 81 deletions(-)
--
2.47.3
^ permalink raw reply
* [RFC PATCH v2 1/3] locking/mutex: Add slow path variants for lock/unlock
From: Yafang Shao @ 2026-03-11 11:52 UTC (permalink / raw)
To: peterz, mingo, will, boqun, longman, rostedt, mhiramat,
mark.rutland, mathieu.desnoyers, david.laight.linux
Cc: linux-kernel, linux-trace-kernel, Yafang Shao
In-Reply-To: <20260311115250.78488-1-laoar.shao@gmail.com>
Background
==========
One of our latency-sensitive services reported random CPU pressure spikes.
After a thorough investigation, we finally identified the root cause of the
CPU pressure spikes. The key kernel stacks are as follows:
- Task A
2026-02-14-16:53:40.938243: [CPU198] 2156302(bpftrace) cgrp:4019437 pod:4019253
find_kallsyms_symbol+142
module_address_lookup+104
kallsyms_lookup_buildid+203
kallsyms_lookup+20
print_rec+64
t_show+67
seq_read_iter+709
seq_read+165
vfs_read+165
ksys_read+103
__x64_sys_read+25
do_syscall_64+56
entry_SYSCALL_64_after_hwframe+100
This task (2156302, bpftrace) is reading the
/sys/kernel/tracing/available_filter_functions to check if a function
is traceable:
https://github.com/bpftrace/bpftrace/blob/master/src/tracefs/tracefs.h#L21
Reading the available_filter_functions file is time-consuming, as it
contains tens of thousands of functions:
$ cat /sys/kernel/tracing/available_filter_functions | wc -l
59221
$ time cat /sys/kernel/tracing/available_filter_functions > /dev/null
real 0m0.458s user 0m0.001s sys 0m0.457s
Consequently, the ftrace_lock is held by this task for an extended period.
- Other Tasks
2026-02-14-16:53:41.437094: [CPU79] 2156308(bpftrace) cgrp:4019437 pod:4019253
mutex_spin_on_owner+108
__mutex_lock.constprop.0+1132
__mutex_lock_slowpath+19
mutex_lock+56
t_start+51
seq_read_iter+250
seq_read+165
vfs_read+165
ksys_read+103
__x64_sys_read+25
do_syscall_64+56
entry_SYSCALL_64_after_hwframe+100
Since ftrace_lock is held by Task-A and Task-A is actively running on a
CPU, all other tasks waiting for the same lock will spin on their
respective CPUs. This leads to increased CPU pressure.
Reproduction
============
This issue can be reproduced simply by running
`cat available_filter_functions`.
- Single process reading available_filter_functions:
$ time cat /sys/kernel/tracing/available_filter_functions > /dev/null
real 0m0.458s user 0m0.001s sys 0m0.457s
- Six processes reading available_filter_functions simultaneously:
for i in `seq 0 5`; do
time cat /sys/kernel/tracing/available_filter_functions > /dev/null &
done
The results are as follows:
real 0m2.666s user 0m0.001s sys 0m2.557s
real 0m2.718s user 0m0.000s sys 0m2.655s
real 0m2.718s user 0m0.001s sys 0m2.600s
real 0m2.733s user 0m0.001s sys 0m2.554s
real 0m2.735s user 0m0.000s sys 0m2.573s
real 0m2.738s user 0m0.000s sys 0m2.664s
As more processes are added, the system time increases correspondingly.
Solution
========
One approach is to optimize the reading of available_filter_functions to
make it as fast as possible. However, the risk lies in the contention
caused by optimistic spin locking.
Therefore, we need to consider an alternative solution that avoids
optimistic spinning for heavy mutexes that may be held for long durations.
Note that we do not want to disable CONFIG_MUTEX_SPIN_ON_OWNER entirely, as
that could lead to unexpected performance regressions.
In this patch, two new APIs are introduced to allow heavy locks to
selectively disable optimistic spinning.
slow_mutex_lock() - lock a mutex without optimistic spinning
slow_mutex_unlock() - unlock the slow mutex
- The result of this optimization
After applying this slow mutex to ftrace_lock and concurrently running six
processes, the results are as follows:
real 0m2.691s user 0m0.001s sys 0m0.458s
real 0m2.785s user 0m0.001s sys 0m0.467s
real 0m2.787s user 0m0.000s sys 0m0.469s
real 0m2.787s user 0m0.000s sys 0m0.466s
real 0m2.788s user 0m0.001s sys 0m0.468s
real 0m2.789s user 0m0.000s sys 0m0.471s
The system time remains similar to that of running a single process.
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
include/linux/mutex.h | 4 ++++
kernel/locking/mutex.c | 41 ++++++++++++++++++++++++++++++++++-------
2 files changed, 38 insertions(+), 7 deletions(-)
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index ecaa0440f6ec..eed0e87c084c 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -189,11 +189,13 @@ extern int __must_check mutex_lock_interruptible_nested(struct mutex *lock,
extern int __must_check _mutex_lock_killable(struct mutex *lock,
unsigned int subclass, struct lockdep_map *nest_lock) __cond_acquires(0, lock);
extern void mutex_lock_io_nested(struct mutex *lock, unsigned int subclass) __acquires(lock);
+extern void slow_mutex_lock_nested(struct mutex *lock, unsigned int subclass);
#define mutex_lock(lock) mutex_lock_nested(lock, 0)
#define mutex_lock_interruptible(lock) mutex_lock_interruptible_nested(lock, 0)
#define mutex_lock_killable(lock) _mutex_lock_killable(lock, 0, NULL)
#define mutex_lock_io(lock) mutex_lock_io_nested(lock, 0)
+#define slow_mutex_lock(lock) slow_mutex_lock_nested(lock, 0)
#define mutex_lock_nest_lock(lock, nest_lock) \
do { \
@@ -215,6 +217,7 @@ extern void mutex_lock(struct mutex *lock) __acquires(lock);
extern int __must_check mutex_lock_interruptible(struct mutex *lock) __cond_acquires(0, lock);
extern int __must_check mutex_lock_killable(struct mutex *lock) __cond_acquires(0, lock);
extern void mutex_lock_io(struct mutex *lock) __acquires(lock);
+extern void slow_mutex_lock(struct mutex *lock) __acquires(lock);
# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
@@ -247,6 +250,7 @@ extern int mutex_trylock(struct mutex *lock) __cond_acquires(true, lock);
#endif
extern void mutex_unlock(struct mutex *lock) __releases(lock);
+#define slow_mutex_unlock(lock) mutex_unlock(lock)
extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) __cond_acquires(true, lock);
diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 2a1d165b3167..5766d824b3fe 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -443,8 +443,11 @@ static inline int mutex_can_spin_on_owner(struct mutex *lock)
*/
static __always_inline bool
mutex_optimistic_spin(struct mutex *lock, struct ww_acquire_ctx *ww_ctx,
- struct mutex_waiter *waiter)
+ struct mutex_waiter *waiter, const bool slow)
{
+ if (slow)
+ return false;
+
if (!waiter) {
/*
* The purpose of the mutex_can_spin_on_owner() function is
@@ -577,7 +580,8 @@ EXPORT_SYMBOL(ww_mutex_unlock);
static __always_inline int __sched
__mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclass,
struct lockdep_map *nest_lock, unsigned long ip,
- struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx)
+ struct ww_acquire_ctx *ww_ctx, const bool use_ww_ctx,
+ const bool slow)
{
DEFINE_WAKE_Q(wake_q);
struct mutex_waiter waiter;
@@ -615,7 +619,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
trace_contention_begin(lock, LCB_F_MUTEX | LCB_F_SPIN);
if (__mutex_trylock(lock) ||
- mutex_optimistic_spin(lock, ww_ctx, NULL)) {
+ mutex_optimistic_spin(lock, ww_ctx, NULL, slow)) {
/* got the lock, yay! */
lock_acquired(&lock->dep_map, ip);
if (ww_ctx)
@@ -716,7 +720,7 @@ __mutex_lock_common(struct mutex *lock, unsigned int state, unsigned int subclas
* to run.
*/
clear_task_blocked_on(current, lock);
- if (mutex_optimistic_spin(lock, ww_ctx, &waiter))
+ if (mutex_optimistic_spin(lock, ww_ctx, &waiter, slow))
break;
set_task_blocked_on(current, lock);
trace_contention_begin(lock, LCB_F_MUTEX);
@@ -773,14 +777,21 @@ static int __sched
__mutex_lock(struct mutex *lock, unsigned int state, unsigned int subclass,
struct lockdep_map *nest_lock, unsigned long ip)
{
- return __mutex_lock_common(lock, state, subclass, nest_lock, ip, NULL, false);
+ return __mutex_lock_common(lock, state, subclass, nest_lock, ip, NULL, false, false);
+}
+
+static int __sched
+__slow_mutex_lock(struct mutex *lock, unsigned int state, unsigned int subclass,
+ struct lockdep_map *nest_lock, unsigned long ip)
+{
+ return __mutex_lock_common(lock, state, subclass, nest_lock, ip, NULL, false, true);
}
static int __sched
__ww_mutex_lock(struct mutex *lock, unsigned int state, unsigned int subclass,
unsigned long ip, struct ww_acquire_ctx *ww_ctx)
{
- return __mutex_lock_common(lock, state, subclass, NULL, ip, ww_ctx, true);
+ return __mutex_lock_common(lock, state, subclass, NULL, ip, ww_ctx, true, false);
}
/**
@@ -861,11 +872,17 @@ mutex_lock_io_nested(struct mutex *lock, unsigned int subclass)
token = io_schedule_prepare();
__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE,
- subclass, NULL, _RET_IP_, NULL, 0);
+ subclass, NULL, _RET_IP_, NULL, 0, false);
io_schedule_finish(token);
}
EXPORT_SYMBOL_GPL(mutex_lock_io_nested);
+void __sched
+slow_mutex_lock_nested(struct mutex *lock, unsigned int subclass)
+{
+ __slow_mutex_lock(lock, TASK_UNINTERRUPTIBLE, subclass, NULL, _RET_IP_);
+}
+
static inline int
ww_mutex_deadlock_injection(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
{
@@ -923,6 +940,16 @@ ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
}
EXPORT_SYMBOL_GPL(ww_mutex_lock_interruptible);
+#else
+
+void __sched slow_mutex_lock(struct mutex *lock)
+{
+ might_sleep();
+
+ if (!__mutex_trylock_fast(lock))
+ __slow_mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, NULL, _RET_IP_);
+}
+
#endif
/*
--
2.47.3
^ permalink raw reply related
* [RFC PATCH v2 2/3] locking/rtmutex: Add slow path variants for lock/unlock
From: Yafang Shao @ 2026-03-11 11:52 UTC (permalink / raw)
To: peterz, mingo, will, boqun, longman, rostedt, mhiramat,
mark.rutland, mathieu.desnoyers, david.laight.linux
Cc: linux-kernel, linux-trace-kernel, Yafang Shao
In-Reply-To: <20260311115250.78488-1-laoar.shao@gmail.com>
Add slow mutex APIs for rtmutex:
slow_rt_mutex_lock: lock a rtmutex without optimistic spinning
slow_rt_mutex_unlock: unlock the slow rtmutex
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
include/linux/rtmutex.h | 3 +++
kernel/locking/rtmutex.c | 37 +++++++++++++++++-----------
kernel/locking/rtmutex_api.c | 47 ++++++++++++++++++++++++++++++------
3 files changed, 66 insertions(+), 21 deletions(-)
diff --git a/include/linux/rtmutex.h b/include/linux/rtmutex.h
index ede4c6bf6f22..22294a916ddc 100644
--- a/include/linux/rtmutex.h
+++ b/include/linux/rtmutex.h
@@ -109,6 +109,7 @@ extern void __rt_mutex_init(struct rt_mutex *lock, const char *name, struct lock
#ifdef CONFIG_DEBUG_LOCK_ALLOC
extern void rt_mutex_lock_nested(struct rt_mutex *lock, unsigned int subclass);
+extern void slow_rt_mutex_lock_nested(struct rt_mutex *lock, unsigned int subclass);
extern void _rt_mutex_lock_nest_lock(struct rt_mutex *lock, struct lockdep_map *nest_lock);
#define rt_mutex_lock(lock) rt_mutex_lock_nested(lock, 0)
#define rt_mutex_lock_nest_lock(lock, nest_lock) \
@@ -116,9 +117,11 @@ extern void _rt_mutex_lock_nest_lock(struct rt_mutex *lock, struct lockdep_map *
typecheck(struct lockdep_map *, &(nest_lock)->dep_map); \
_rt_mutex_lock_nest_lock(lock, &(nest_lock)->dep_map); \
} while (0)
+#define slow_rt_mutex_lock(lock) slow_rt_mutex_lock_nested(lock, 0)
#else
extern void rt_mutex_lock(struct rt_mutex *lock);
+extern void slow_rt_mutex_lock(struct rt_mutex *lock);
#define rt_mutex_lock_nested(lock, subclass) rt_mutex_lock(lock)
#define rt_mutex_lock_nest_lock(lock, nest_lock) rt_mutex_lock(lock)
#endif
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index c80902eacd79..663ff96cb1be 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -1480,10 +1480,13 @@ static __always_inline void __rt_mutex_unlock(struct rt_mutex_base *lock)
#ifdef CONFIG_SMP
static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock,
struct rt_mutex_waiter *waiter,
- struct task_struct *owner)
+ struct task_struct *owner,
+ const bool slow)
{
bool res = true;
+ if (slow)
+ return false;
rcu_read_lock();
for (;;) {
/* If owner changed, trylock again. */
@@ -1517,7 +1520,8 @@ static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock,
#else
static bool rtmutex_spin_on_owner(struct rt_mutex_base *lock,
struct rt_mutex_waiter *waiter,
- struct task_struct *owner)
+ struct task_struct *owner,
+ const bool slow)
{
return false;
}
@@ -1606,7 +1610,8 @@ static int __sched rt_mutex_slowlock_block(struct rt_mutex_base *lock,
unsigned int state,
struct hrtimer_sleeper *timeout,
struct rt_mutex_waiter *waiter,
- struct wake_q_head *wake_q)
+ struct wake_q_head *wake_q,
+ const bool slow)
__releases(&lock->wait_lock) __acquires(&lock->wait_lock)
{
struct rt_mutex *rtm = container_of(lock, struct rt_mutex, rtmutex);
@@ -1642,7 +1647,7 @@ static int __sched rt_mutex_slowlock_block(struct rt_mutex_base *lock,
owner = NULL;
raw_spin_unlock_irq_wake(&lock->wait_lock, wake_q);
- if (!owner || !rtmutex_spin_on_owner(lock, waiter, owner)) {
+ if (!owner || !rtmutex_spin_on_owner(lock, waiter, owner, slow)) {
lockevent_inc(rtmutex_slow_sleep);
rt_mutex_schedule();
}
@@ -1693,7 +1698,8 @@ static int __sched __rt_mutex_slowlock(struct rt_mutex_base *lock,
unsigned int state,
enum rtmutex_chainwalk chwalk,
struct rt_mutex_waiter *waiter,
- struct wake_q_head *wake_q)
+ struct wake_q_head *wake_q,
+ const bool slow)
{
struct rt_mutex *rtm = container_of(lock, struct rt_mutex, rtmutex);
struct ww_mutex *ww = ww_container_of(rtm);
@@ -1718,7 +1724,7 @@ static int __sched __rt_mutex_slowlock(struct rt_mutex_base *lock,
ret = task_blocks_on_rt_mutex(lock, waiter, current, ww_ctx, chwalk, wake_q);
if (likely(!ret))
- ret = rt_mutex_slowlock_block(lock, ww_ctx, state, NULL, waiter, wake_q);
+ ret = rt_mutex_slowlock_block(lock, ww_ctx, state, NULL, waiter, wake_q, slow);
if (likely(!ret)) {
/* acquired the lock */
@@ -1749,7 +1755,8 @@ static int __sched __rt_mutex_slowlock(struct rt_mutex_base *lock,
static inline int __rt_mutex_slowlock_locked(struct rt_mutex_base *lock,
struct ww_acquire_ctx *ww_ctx,
unsigned int state,
- struct wake_q_head *wake_q)
+ struct wake_q_head *wake_q,
+ const bool slow)
{
struct rt_mutex_waiter waiter;
int ret;
@@ -1758,7 +1765,7 @@ static inline int __rt_mutex_slowlock_locked(struct rt_mutex_base *lock,
waiter.ww_ctx = ww_ctx;
ret = __rt_mutex_slowlock(lock, ww_ctx, state, RT_MUTEX_MIN_CHAINWALK,
- &waiter, wake_q);
+ &waiter, wake_q, slow);
debug_rt_mutex_free_waiter(&waiter);
lockevent_cond_inc(rtmutex_slow_wake, !wake_q_empty(wake_q));
@@ -1773,7 +1780,8 @@ static inline int __rt_mutex_slowlock_locked(struct rt_mutex_base *lock,
*/
static int __sched rt_mutex_slowlock(struct rt_mutex_base *lock,
struct ww_acquire_ctx *ww_ctx,
- unsigned int state)
+ unsigned int state,
+ const bool slow)
{
DEFINE_WAKE_Q(wake_q);
unsigned long flags;
@@ -1797,7 +1805,7 @@ static int __sched rt_mutex_slowlock(struct rt_mutex_base *lock,
* irqsave/restore variants.
*/
raw_spin_lock_irqsave(&lock->wait_lock, flags);
- ret = __rt_mutex_slowlock_locked(lock, ww_ctx, state, &wake_q);
+ ret = __rt_mutex_slowlock_locked(lock, ww_ctx, state, &wake_q, slow);
raw_spin_unlock_irqrestore_wake(&lock->wait_lock, flags, &wake_q);
rt_mutex_post_schedule();
@@ -1805,14 +1813,14 @@ static int __sched rt_mutex_slowlock(struct rt_mutex_base *lock,
}
static __always_inline int __rt_mutex_lock(struct rt_mutex_base *lock,
- unsigned int state)
+ unsigned int state, const bool slow)
{
lockdep_assert(!current->pi_blocked_on);
if (likely(rt_mutex_try_acquire(lock)))
return 0;
- return rt_mutex_slowlock(lock, NULL, state);
+ return rt_mutex_slowlock(lock, NULL, state, slow);
}
#endif /* RT_MUTEX_BUILD_MUTEX */
@@ -1827,7 +1835,8 @@ static __always_inline int __rt_mutex_lock(struct rt_mutex_base *lock,
* @wake_q: The wake_q to wake tasks after we release the wait_lock
*/
static void __sched rtlock_slowlock_locked(struct rt_mutex_base *lock,
- struct wake_q_head *wake_q)
+ struct wake_q_head *wake_q,
+ const bool slow)
__releases(&lock->wait_lock) __acquires(&lock->wait_lock)
{
struct rt_mutex_waiter waiter;
@@ -1863,7 +1872,7 @@ static void __sched rtlock_slowlock_locked(struct rt_mutex_base *lock,
owner = NULL;
raw_spin_unlock_irq_wake(&lock->wait_lock, wake_q);
- if (!owner || !rtmutex_spin_on_owner(lock, &waiter, owner)) {
+ if (!owner || !rtmutex_spin_on_owner(lock, &waiter, owner, slow)) {
lockevent_inc(rtlock_slow_sleep);
schedule_rtlock();
}
diff --git a/kernel/locking/rtmutex_api.c b/kernel/locking/rtmutex_api.c
index 59dbd29cb219..b196cdd35ff1 100644
--- a/kernel/locking/rtmutex_api.c
+++ b/kernel/locking/rtmutex_api.c
@@ -37,21 +37,29 @@ subsys_initcall(init_rtmutex_sysctl);
* The atomic acquire/release ops are compiled away, when either the
* architecture does not support cmpxchg or when debugging is enabled.
*/
-static __always_inline int __rt_mutex_lock_common(struct rt_mutex *lock,
+static __always_inline int ___rt_mutex_lock_common(struct rt_mutex *lock,
unsigned int state,
struct lockdep_map *nest_lock,
- unsigned int subclass)
+ unsigned int subclass,
+ const bool slow)
{
int ret;
might_sleep();
mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, _RET_IP_);
- ret = __rt_mutex_lock(&lock->rtmutex, state);
+ ret = __rt_mutex_lock(&lock->rtmutex, state, slow);
if (ret)
mutex_release(&lock->dep_map, _RET_IP_);
return ret;
}
+static __always_inline int __rt_mutex_lock_common(struct rt_mutex *lock,
+ unsigned int state,
+ struct lockdep_map *nest_lock,
+ unsigned int subclass)
+{
+ return ___rt_mutex_lock_common(lock, state, nest_lock, subclass, false);
+}
void rt_mutex_base_init(struct rt_mutex_base *rtb)
{
__rt_mutex_base_init(rtb);
@@ -77,6 +85,11 @@ void __sched _rt_mutex_lock_nest_lock(struct rt_mutex *lock, struct lockdep_map
}
EXPORT_SYMBOL_GPL(_rt_mutex_lock_nest_lock);
+void __sched slow_rt_mutex_lock_nested(struct rt_mutex *lock, unsigned int subclass)
+{
+ ___rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, NULL, subclass, true);
+}
+
#else /* !CONFIG_DEBUG_LOCK_ALLOC */
/**
@@ -89,6 +102,11 @@ void __sched rt_mutex_lock(struct rt_mutex *lock)
__rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, NULL, 0);
}
EXPORT_SYMBOL_GPL(rt_mutex_lock);
+
+void __sched slow_rt_mutex_lock(struct rt_mutex *lock)
+{
+ ___rt_mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, NULL, 0, true);
+}
#endif
/**
@@ -401,7 +419,7 @@ int __sched rt_mutex_wait_proxy_lock(struct rt_mutex_base *lock,
raw_spin_lock_irq(&lock->wait_lock);
/* sleep on the mutex */
set_current_state(TASK_INTERRUPTIBLE);
- ret = rt_mutex_slowlock_block(lock, NULL, TASK_INTERRUPTIBLE, to, waiter, NULL);
+ ret = rt_mutex_slowlock_block(lock, NULL, TASK_INTERRUPTIBLE, to, waiter, NULL, false);
/*
* try_to_take_rt_mutex() sets the waiter bit unconditionally. We might
* have to fix that up.
@@ -521,17 +539,18 @@ static void __mutex_rt_init_generic(struct mutex *mutex)
debug_check_no_locks_freed((void *)mutex, sizeof(*mutex));
}
-static __always_inline int __mutex_lock_common(struct mutex *lock,
+static __always_inline int ___mutex_lock_common(struct mutex *lock,
unsigned int state,
unsigned int subclass,
struct lockdep_map *nest_lock,
- unsigned long ip)
+ unsigned long ip,
+ const bool slow)
{
int ret;
might_sleep();
mutex_acquire_nest(&lock->dep_map, subclass, 0, nest_lock, ip);
- ret = __rt_mutex_lock(&lock->rtmutex, state);
+ ret = __rt_mutex_lock(&lock->rtmutex, state, slow);
if (ret)
mutex_release(&lock->dep_map, ip);
else
@@ -539,6 +558,15 @@ static __always_inline int __mutex_lock_common(struct mutex *lock,
return ret;
}
+static __always_inline int __mutex_lock_common(struct mutex *lock,
+ unsigned int state,
+ unsigned int subclass,
+ struct lockdep_map *nest_lock,
+ unsigned long ip)
+{
+ ___mutex_lock_common(lock, state, subclass, nest_lock, ip, false);
+}
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC
void mutex_rt_init_lockdep(struct mutex *mutex, const char *name, struct lock_class_key *key)
{
@@ -644,6 +672,11 @@ int __sched mutex_trylock(struct mutex *lock)
return __rt_mutex_trylock(&lock->rtmutex);
}
EXPORT_SYMBOL(mutex_trylock);
+
+void __sched slow_mutex_lock(struct mutex *lock)
+{
+ ___mutex_lock_common(lock, state, subclass, nest_lock, ip, true);
+}
#endif /* !CONFIG_DEBUG_LOCK_ALLOC */
void __sched mutex_unlock(struct mutex *lock)
--
2.47.3
^ permalink raw reply related
* [RFC PATCH v2 3/3] ftrace: Disable optimistic spinning for ftrace_lock
From: Yafang Shao @ 2026-03-11 11:52 UTC (permalink / raw)
To: peterz, mingo, will, boqun, longman, rostedt, mhiramat,
mark.rutland, mathieu.desnoyers, david.laight.linux
Cc: linux-kernel, linux-trace-kernel, Yafang Shao
In-Reply-To: <20260311115250.78488-1-laoar.shao@gmail.com>
The ftrace_lock may be held for a relatively long duration. For example,
reading the available_filter_functions file takes considerable time:
$ time cat /sys/kernel/tracing/available_filter_functions &> /dev/null
real 0m0.457s user 0m0.001s sys 0m0.455s
When the lock owner is continuously running, other tasks waiting for the
lock will spin repeatedly until they hit a cond_resched() point, wasting
CPU cycles.
ftrace_lock is currently used in the following scenarios:
- Debugging
- Live patching
Neither of these scenarios are in the application critical path.
Therefore, it is reasonable to make tasks sleep when they cannot acquire
the lock immediately, rather than spinning and consuming CPU resources.
Performance Comparison
======================
- Before this change
- Single task reading available_filter_functions:
real 0m0.457s user 0m0.001s sys 0m0.455s
- Six concurrent processes:
real 0m2.666s user 0m0.001s sys 0m2.557s
real 0m2.718s user 0m0.000s sys 0m2.655s
real 0m2.718s user 0m0.001s sys 0m2.600s
real 0m2.733s user 0m0.001s sys 0m2.554s
real 0m2.735s user 0m0.000s sys 0m2.573s
real 0m2.738s user 0m0.000s sys 0m2.664s
- After this change
- Single task:
real 0m0.454s user 0m0.002s sys 0m0.453s
- Six concurrent processes:
real 0m2.691s user 0m0.001s sys 0m0.458s
real 0m2.785s user 0m0.001s sys 0m0.467s
real 0m2.787s user 0m0.000s sys 0m0.469s
real 0m2.787s user 0m0.000s sys 0m0.466s
real 0m2.788s user 0m0.001s sys 0m0.468s
real 0m2.789s user 0m0.000s sys 0m0.471s
The system time significantly decreases in the concurrent case, as tasks
now sleep while waiting for the lock instead of busy-spinning.
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
kernel/trace/ftrace.c | 106 +++++++++++++++++++++---------------------
1 file changed, 53 insertions(+), 53 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 827fb9a0bf0d..00c195e280c5 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1284,10 +1284,10 @@ static void clear_ftrace_mod_list(struct list_head *head)
if (!head)
return;
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
list_for_each_entry_safe(p, n, head, list)
free_ftrace_mod(p);
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
}
void free_ftrace_hash(struct ftrace_hash *hash)
@@ -4254,7 +4254,7 @@ static void *t_start(struct seq_file *m, loff_t *pos)
void *p = NULL;
loff_t l;
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
if (unlikely(ftrace_disabled))
return NULL;
@@ -4305,7 +4305,7 @@ static void *t_start(struct seq_file *m, loff_t *pos)
static void t_stop(struct seq_file *m, void *p)
{
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
}
void * __weak
@@ -4362,11 +4362,11 @@ static __init void ftrace_check_work_func(struct work_struct *work)
struct ftrace_page *pg;
struct dyn_ftrace *rec;
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
do_for_each_ftrace_rec(pg, rec) {
test_for_valid_rec(rec);
} while_for_each_ftrace_rec();
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
}
static int __init ftrace_check_for_weak_functions(void)
@@ -5123,7 +5123,7 @@ static void process_mod_list(struct list_head *head, struct ftrace_ops *ops,
if (!new_hash)
goto out; /* warn? */
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
list_for_each_entry_safe(ftrace_mod, n, head, list) {
@@ -5145,7 +5145,7 @@ static void process_mod_list(struct list_head *head, struct ftrace_ops *ops,
ftrace_mod->func = func;
}
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
list_for_each_entry_safe(ftrace_mod, n, &process_mods, list) {
@@ -5159,11 +5159,11 @@ static void process_mod_list(struct list_head *head, struct ftrace_ops *ops,
if (enable && list_empty(head))
new_hash->flags &= ~FTRACE_HASH_FL_MOD;
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
ftrace_hash_move_and_update_ops(ops, orig_hash,
new_hash, enable);
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
out:
mutex_unlock(&ops->func_hash->regex_lock);
@@ -5465,7 +5465,7 @@ register_ftrace_function_probe(char *glob, struct trace_array *tr,
return -EINVAL;
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
/* Check if the probe_ops is already registered */
list_for_each_entry(iter, &tr->func_probes, list) {
if (iter->probe_ops == probe_ops) {
@@ -5476,7 +5476,7 @@ register_ftrace_function_probe(char *glob, struct trace_array *tr,
if (!probe) {
probe = kzalloc_obj(*probe);
if (!probe) {
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
return -ENOMEM;
}
probe->probe_ops = probe_ops;
@@ -5488,7 +5488,7 @@ register_ftrace_function_probe(char *glob, struct trace_array *tr,
acquire_probe_locked(probe);
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
/*
* Note, there's a small window here that the func_hash->filter_hash
@@ -5540,7 +5540,7 @@ register_ftrace_function_probe(char *glob, struct trace_array *tr,
}
}
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
if (!count) {
/* Nothing was added? */
@@ -5560,7 +5560,7 @@ register_ftrace_function_probe(char *glob, struct trace_array *tr,
ret = ftrace_startup(&probe->ops, 0);
out_unlock:
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
if (!ret)
ret = count;
@@ -5619,7 +5619,7 @@ unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr,
return -EINVAL;
}
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
/* Check if the probe_ops is already registered */
list_for_each_entry(iter, &tr->func_probes, list) {
if (iter->probe_ops == probe_ops) {
@@ -5636,7 +5636,7 @@ unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr,
acquire_probe_locked(probe);
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
mutex_lock(&probe->ops.func_hash->regex_lock);
@@ -5679,7 +5679,7 @@ unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr,
goto out_unlock;
}
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
WARN_ON(probe->ref < count);
@@ -5703,7 +5703,7 @@ unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr,
probe_ops->free(probe_ops, tr, entry->ip, probe->data);
kfree(entry);
}
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
out_unlock:
mutex_unlock(&probe->ops.func_hash->regex_lock);
@@ -5714,7 +5714,7 @@ unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr,
return ret;
err_unlock_ftrace:
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
return ret;
}
@@ -5943,9 +5943,9 @@ ftrace_set_hash(struct ftrace_ops *ops, unsigned char *buf, int len,
goto out_regex_unlock;
}
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
ret = ftrace_hash_move_and_update_ops(ops, orig_hash, hash, enable);
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
out_regex_unlock:
mutex_unlock(&ops->func_hash->regex_lock);
@@ -6205,7 +6205,7 @@ __modify_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
* Now the ftrace_ops_list_func() is called to do the direct callers.
* We can safely change the direct functions attached to each entry.
*/
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
size = 1 << hash->size_bits;
for (i = 0; i < size; i++) {
@@ -6219,7 +6219,7 @@ __modify_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
/* Prevent store tearing if a trampoline concurrently accesses the value */
WRITE_ONCE(ops->direct_call, addr);
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
out:
/* Removing the tmp_ops will add the updated direct callers to the functions */
@@ -6625,7 +6625,7 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, b
* Now the ftrace_ops_list_func() is called to do the direct callers.
* We can safely change the direct functions attached to each entry.
*/
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
size = 1 << hash->size_bits;
for (i = 0; i < size; i++) {
@@ -6637,7 +6637,7 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, b
}
}
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
out:
/* Removing the tmp_ops will add the updated direct callers to the functions */
@@ -6980,10 +6980,10 @@ int ftrace_regex_release(struct inode *inode, struct file *file)
} else
orig_hash = &iter->ops->func_hash->notrace_hash;
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
ftrace_hash_move_and_update_ops(iter->ops, orig_hash,
iter->hash, filter_hash);
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
}
mutex_unlock(&iter->ops->func_hash->regex_lock);
@@ -7464,12 +7464,12 @@ void ftrace_create_filter_files(struct ftrace_ops *ops,
*/
void ftrace_destroy_filter_files(struct ftrace_ops *ops)
{
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
if (ops->flags & FTRACE_OPS_FL_ENABLED)
ftrace_shutdown(ops, 0);
ops->flags |= FTRACE_OPS_FL_DELETED;
ftrace_free_filter(ops);
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
}
static __init int ftrace_init_dyn_tracefs(struct dentry *d_tracer)
@@ -7571,7 +7571,7 @@ static int ftrace_process_locs(struct module *mod,
if (!start_pg)
return -ENOMEM;
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
/*
* Core and each module needs their own pages, as
@@ -7661,7 +7661,7 @@ static int ftrace_process_locs(struct module *mod,
local_irq_restore(flags);
ret = 0;
out:
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
/* We should have used all pages unless we skipped some */
if (pg_unuse) {
@@ -7868,7 +7868,7 @@ void ftrace_release_mod(struct module *mod)
struct ftrace_page *tmp_page = NULL;
struct ftrace_page *pg;
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
/*
* To avoid the UAF problem after the module is unloaded, the
@@ -7913,7 +7913,7 @@ void ftrace_release_mod(struct module *mod)
last_pg = &pg->next;
}
out_unlock:
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
/* Need to synchronize with ftrace_location_range() */
if (tmp_page)
@@ -7938,7 +7938,7 @@ void ftrace_module_enable(struct module *mod)
struct dyn_ftrace *rec;
struct ftrace_page *pg;
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
if (ftrace_disabled)
goto out_unlock;
@@ -8008,7 +8008,7 @@ void ftrace_module_enable(struct module *mod)
ftrace_arch_code_modify_post_process();
out_unlock:
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
process_cached_mods(mod->name);
}
@@ -8267,7 +8267,7 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr)
key.ip = start;
key.flags = end; /* overload flags, as it is unsigned long */
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
/*
* If we are freeing module init memory, then check if
@@ -8310,7 +8310,7 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr)
/* More than one function may be in this block */
goto again;
}
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
list_for_each_entry_safe(func, func_next, &clear_hash, list) {
clear_func_from_hashes(func);
@@ -8686,22 +8686,22 @@ static void clear_ftrace_pids(struct trace_array *tr, int type)
void ftrace_clear_pids(struct trace_array *tr)
{
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
clear_ftrace_pids(tr, TRACE_PIDS | TRACE_NO_PIDS);
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
}
static void ftrace_pid_reset(struct trace_array *tr, int type)
{
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
clear_ftrace_pids(tr, type);
ftrace_update_pid_func();
ftrace_startup_all(0);
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
}
/* Greater than any max PID */
@@ -8713,7 +8713,7 @@ static void *fpid_start(struct seq_file *m, loff_t *pos)
struct trace_pid_list *pid_list;
struct trace_array *tr = m->private;
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
rcu_read_lock_sched();
pid_list = rcu_dereference_sched(tr->function_pids);
@@ -8740,7 +8740,7 @@ static void fpid_stop(struct seq_file *m, void *p)
__releases(RCU)
{
rcu_read_unlock_sched();
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
}
static int fpid_show(struct seq_file *m, void *v)
@@ -8766,7 +8766,7 @@ static void *fnpid_start(struct seq_file *m, loff_t *pos)
struct trace_pid_list *pid_list;
struct trace_array *tr = m->private;
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
rcu_read_lock_sched();
pid_list = rcu_dereference_sched(tr->function_no_pids);
@@ -9057,7 +9057,7 @@ static int prepare_direct_functions_for_ipmodify(struct ftrace_ops *ops)
unsigned long ip = entry->ip;
bool found_op = false;
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
do_for_each_ftrace_op(op, ftrace_ops_list) {
if (!(op->flags & FTRACE_OPS_FL_DIRECT))
continue;
@@ -9066,7 +9066,7 @@ static int prepare_direct_functions_for_ipmodify(struct ftrace_ops *ops)
break;
}
} while_for_each_ftrace_op(op);
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
if (found_op) {
if (!op->ops_func)
@@ -9106,7 +9106,7 @@ static void cleanup_direct_functions_after_ipmodify(struct ftrace_ops *ops)
unsigned long ip = entry->ip;
bool found_op = false;
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
do_for_each_ftrace_op(op, ftrace_ops_list) {
if (!(op->flags & FTRACE_OPS_FL_DIRECT))
continue;
@@ -9115,7 +9115,7 @@ static void cleanup_direct_functions_after_ipmodify(struct ftrace_ops *ops)
break;
}
} while_for_each_ftrace_op(op);
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
/* The cleanup is optional, ignore any errors */
if (found_op && op->ops_func)
@@ -9153,11 +9153,11 @@ static int register_ftrace_function_nolock(struct ftrace_ops *ops)
ftrace_ops_init(ops);
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
ret = ftrace_startup(ops, 0);
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
return ret;
}
@@ -9200,9 +9200,9 @@ int unregister_ftrace_function(struct ftrace_ops *ops)
{
int ret;
- mutex_lock(&ftrace_lock);
+ slow_mutex_lock(&ftrace_lock);
ret = ftrace_shutdown(ops, 0);
- mutex_unlock(&ftrace_lock);
+ slow_mutex_unlock(&ftrace_lock);
cleanup_direct_functions_after_ipmodify(ops);
return ret;
--
2.47.3
^ permalink raw reply related
* Re: [RFC PATCH v2 0/3] disable optimistic spinning for ftrace_lock
From: Peter Zijlstra @ 2026-03-11 11:54 UTC (permalink / raw)
To: Yafang Shao
Cc: mingo, will, boqun, longman, rostedt, mhiramat, mark.rutland,
mathieu.desnoyers, david.laight.linux, linux-kernel,
linux-trace-kernel
In-Reply-To: <20260311115250.78488-1-laoar.shao@gmail.com>
On Wed, Mar 11, 2026 at 07:52:47PM +0800, Yafang Shao wrote:
> Recently, we resolved a latency spike issue caused by concurrently running
> bpftrace processes. The root cause was high contention on the ftrace_lock
> due to optimistic spinning. We can optimize this by disabling optimistic
> spinning for ftrace_lock.
>
> While semaphores may present similar challenges, I'm not currently aware of
> specific instances that exhibit this exact issue. Should we encounter
> problematic semaphores in production workloads, we can address them at that
> time.
>
> PATCH #1: introduce slow_mutex_[un]lock to disable optimistic spinning
> PATCH #2: add variant for rtmutex
> PATCH #3: disable optimistic spinning for ftrace_lock
>
So I really utterly hate this.
^ permalink raw reply
* Re: [RFC PATCH v2 0/3] disable optimistic spinning for ftrace_lock
From: Yafang Shao @ 2026-03-11 11:55 UTC (permalink / raw)
To: Peter Zijlstra
Cc: mingo, will, boqun, longman, rostedt, mhiramat, mark.rutland,
mathieu.desnoyers, david.laight.linux, linux-kernel,
linux-trace-kernel
In-Reply-To: <20260311115426.GN606826@noisy.programming.kicks-ass.net>
On Wed, Mar 11, 2026 at 7:54 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Wed, Mar 11, 2026 at 07:52:47PM +0800, Yafang Shao wrote:
> > Recently, we resolved a latency spike issue caused by concurrently running
> > bpftrace processes. The root cause was high contention on the ftrace_lock
> > due to optimistic spinning. We can optimize this by disabling optimistic
> > spinning for ftrace_lock.
> >
> > While semaphores may present similar challenges, I'm not currently aware of
> > specific instances that exhibit this exact issue. Should we encounter
> > problematic semaphores in production workloads, we can address them at that
> > time.
> >
> > PATCH #1: introduce slow_mutex_[un]lock to disable optimistic spinning
> > PATCH #2: add variant for rtmutex
> > PATCH #3: disable optimistic spinning for ftrace_lock
> >
>
> So I really utterly hate this.
Do you have any other suggestions for optimizing this?
--
Regards
Yafang
^ permalink raw reply
* Re: [RFC PATCH v2 0/3] disable optimistic spinning for ftrace_lock
From: David Laight @ 2026-03-11 12:53 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Yafang Shao, mingo, will, boqun, longman, rostedt, mhiramat,
mark.rutland, mathieu.desnoyers, linux-kernel, linux-trace-kernel
In-Reply-To: <20260311115426.GN606826@noisy.programming.kicks-ass.net>
On Wed, 11 Mar 2026 12:54:26 +0100
Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Mar 11, 2026 at 07:52:47PM +0800, Yafang Shao wrote:
> > Recently, we resolved a latency spike issue caused by concurrently running
> > bpftrace processes. The root cause was high contention on the ftrace_lock
> > due to optimistic spinning. We can optimize this by disabling optimistic
> > spinning for ftrace_lock.
> >
> > While semaphores may present similar challenges, I'm not currently aware of
> > specific instances that exhibit this exact issue. Should we encounter
> > problematic semaphores in production workloads, we can address them at that
> > time.
> >
> > PATCH #1: introduce slow_mutex_[un]lock to disable optimistic spinning
> > PATCH #2: add variant for rtmutex
> > PATCH #3: disable optimistic spinning for ftrace_lock
> >
>
> So I really utterly hate this.
Yep...
Adding the extra parameter is likely to have a measurable impact
on everything else.
The problematic path is obvious: find_kallsyms_symbol+142
module_address_lookup+104
kallsyms_lookup_buildid+203
kallsyms_lookup+20
print_rec+64
t_show+67
seq_read_iter+709
seq_read+165
vfs_read+165
ksys_read+103
__x64_sys_read+25
do_syscall_64+56
entry_SYSCALL_64_after_hwframe+100
The code needs to drop the ftrace_lock across t_show.
Although there is a bigger issue of why on earth the code is reading the
list of filter functions at all - never mind all the time.
I'll do it by hand when debugging, but I'd have though anything using bpf
will know exactly where to add its hooks.
David
^ permalink raw reply
* [PATCH v3 0/4] tracing/preemptirq: Optimize disabled tracepoint overhead
From: Wander Lairson Costa @ 2026-03-11 12:50 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
Dietmar Eggemann, Steven Rostedt, Ben Segall, Mel Gorman,
Valentin Schneider, Masami Hiramatsu, Mathieu Desnoyers,
Andrew Morton, open list:SCHEDULER, open list:TRACING
Cc: acme, williams, gmonaco, Wander Lairson Costa
The preempt and IRQ tracepoints currently impose measurable overhead
even when they are compiled in but not actively enabled. This overhead
stems from external function calls and unconditional tracepoint checks
in highly active code paths.
The v2 series optimized within the existing CONFIG_TRACE_IRQFLAGS
path, which still required the heavy lockdep and irqsoff
infrastructure to be enabled. This v3 takes a different approach by
providing independent, user-selectable configurations
(CONFIG_TRACE_PREEMPT_TOGGLE and CONFIG_TRACE_IRQFLAGS_TOGGLE) that
expose the tracepoints without pulling in the heavier infrastructure.
The preempt optimization uses inline static key checks, while the IRQ
optimization employs lightweight wrapper functions that check raw
hardware state. Making both configurations explicitly user-selectable
addresses upstream feedback regarding the impact on code generation,
ensuring that this optimization remains strictly opt-in.
---
Performance Measurements
Measurements were taken using the tracer-benchmark kernel module [1].
The module creates one kthread per online CPU. Each thread performs
a configurable number of iterations of
local_irq_disable()/local_irq_enable() and
preempt_disable()/preempt_enable() pairs, timing each pair with
ktime_get_ns(). All threads start simultaneously via a completion
to maximize contention. Per-CPU results (average, median) are aggregated across
CPUs. The 99th percentile is measured separately
on a single pinned CPU. The kernel used was version 7.0.0. All
values are in nanoseconds. Each run collected 10^7 samples.
Configurations compared:
- 7.0.0: stock kernel
- irqsoff: stock kernel with CONFIG_IRQSOFF_TRACER=y and
CONFIG_PREEMPT_TRACER=y
- preemptirq: patched kernel with CONFIG_TRACE_PREEMPT_TOGGLE=y
and CONFIG_TRACE_IRQFLAGS_TOGGLE=y
The '+' suffix indicates the test ran with tracepoints enabled.
IRQ Metrics
Metric 7.0.0 irqsoff irqsoff+ preemptirq preemptirq+
average 19 27 175 19 166
median 19 27 172 19 164
99 percentile 21 29 234 21 221
Preempt Metrics
Metric 7.0.0 irqsoff irqsoff+ preemptirq preemptirq+
average 16 21 169 16 160
median 16 21 165 17 159
99 percentile 18 23 236 18 217
The preemptirq configuration matches the stock kernel performance
when tracepoints are disabled, while the irqsoff configuration adds
~40% overhead even when inactive. When tracepoints are enabled,
preemptirq is also slightly faster than irqsoff.
Binary size impact (stripped vmlinux, defconfig):
7.0.0: 43404576 bytes
preemptirq: 43429152 bytes (+24576 bytes, +0.057%)
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
---
References:
[1] https://github.com/walac/tracer-benchmark
Changes in v3:
- Reworked series from 2 to 4 patches
- IRQ tracing rearchitected: instead of optimizing within
CONFIG_TRACE_IRQFLAGS, introduced independent
CONFIG_TRACE_IRQFLAGS_TOGGLE that provides irq_disable/irq_enable
tracepoints without pulling in lockdep or irqsoff infrastructure
- Made TRACE_PREEMPT_TOGGLE user-selectable in Kconfig, addressing
upstream feedback about code generation impact
- Preempt optimization now handles CONFIG_PREEMPT_TRACER alongside
CONFIG_DEBUG_PREEMPT in the three-way #if split
- Fixed __preempt_trace_enabled() macro to accept val as parameter
- Resolved circular header dependency on m68k by placing
tracepoint-defs.h include inside conditional blocks instead of
at the top of preempt.h and irqflags.h
- Moved atomic.h include from tracepoint-defs.h to tracepoint.h
to break circular dependency chain on ARM32
- Used EXPORT_TRACEPOINT_SYMBOL() instead of raw
EXPORT_SYMBOL(__tracepoint_*) for proper tracepoint registration
- Narrowed core.c compilation guard to CONFIG_DEBUG_PREEMPT ||
CONFIG_PREEMPT_TRACER since TRACE_PREEMPT_TOGGLE is now handled
inline
- Updated performance benchmarks on 7.0.0, including
tracepoint-enabled measurements and binary size impact
Changes in v2:
- Fixed build failure on arm32 (circular dependency:
atomic.h -> cmpxchg.h -> irqflags.h -> tracepoint.h -> atomic.h)
Wander Lairson Costa (4):
tracing/preemptirq: Optimize preempt_disable/enable() tracepoint
overhead
trace/preemptirq: make TRACE_PREEMPT_TOGGLE user-selectable
trace/preemptirq: add TRACE_IRQFLAGS_TOGGLE
trace/preemptirq: Implement trace_irqflags hooks
include/linux/irqflags.h | 62 +++++++++++++++++++++++++++-
include/linux/preempt.h | 49 ++++++++++++++++++++--
include/linux/tracepoint-defs.h | 1 -
include/linux/tracepoint.h | 1 +
include/trace/events/preemptirq.h | 2 +-
kernel/sched/core.c | 2 +-
kernel/trace/Kconfig | 19 +++++++--
kernel/trace/trace_preemptirq.c | 68 +++++++++++++++++++++++++++++++
8 files changed, 193 insertions(+), 11 deletions(-)
--
2.53.0
^ permalink raw reply
* [PATCH v3 1/4] tracing/preemptirq: Optimize preempt_disable/enable() tracepoint overhead
From: Wander Lairson Costa @ 2026-03-11 12:50 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
Dietmar Eggemann, Steven Rostedt, Ben Segall, Mel Gorman,
Valentin Schneider, Masami Hiramatsu, Mathieu Desnoyers,
Andrew Morton, open list:SCHEDULER, open list:TRACING
Cc: acme, williams, gmonaco, Wander Lairson Costa
In-Reply-To: <20260311125021.197638-1-wander@redhat.com>
When CONFIG_TRACE_PREEMPT_TOGGLE is enabled, preempt_count_add() and
preempt_count_sub() become external function calls (defined in
kernel/sched/core.c) rather than inlined operations. These functions
also perform preempt_count() checks and call trace_preempt_on/off()
unconditionally, even when no tracing consumer is active.
Reduce this overhead by splitting the #if logic in preempt.h into
three cases. When CONFIG_DEBUG_PREEMPT or CONFIG_PREEMPT_TRACER is
set, keep external function calls because DEBUG_PREEMPT needs runtime
validation checks, and PREEMPT_TRACER needs the preemptoff latency
tracer hooks (tracer_preempt_on/off, called via trace_preempt_on/off).
When CONFIG_TRACE_PREEMPT_TOGGLE alone is set, provide new inline
versions of preempt_count_add/sub() that check the tracepoint static
key via the __preempt_trace_enabled() macro before calling into the
tracing path. The macro evaluates to true when the preempt_enable or
preempt_disable tracepoint has subscribers AND the preempt count
equals val (indicating the first preempt disable or last preempt
enable), preserving the original preempt_latency_start/stop semantics.
When none of the above are set, use pure inline macros with no tracing
overhead.
The preempt_count_dec_and_test() macro is refactored out of the
three-way #if into a separate block shared by the first two cases,
since both need it to call the (potentially inline)
preempt_count_sub() before checking should_resched().
The inline path calls thin __trace_preempt_on/off() wrappers (added
in trace_preemptirq.c) that invoke trace_preempt_on/off(), keeping
the full tracepoint machinery out of the inline code.
The #include <linux/tracepoint-defs.h> is placed inside the
CONFIG_TRACE_PREEMPT_TOGGLE block rather than at the top of the file
to avoid a circular include dependency on architectures where
asm/irqflags.h includes linux/preempt.h (e.g. m68k):
preempt.h -> tracepoint-defs.h -> static_key.h -> jump_label.h ->
atomic.h -> irqflags.h -> asm/irqflags.h -> preempt.h (guarded)
If the include were at the top, this chain would be traversed before
hardirq_count() is defined (at line 110), causing a build failure on
m68k. Placing it inside the #elif block ensures it is only pulled in
when CONFIG_TRACE_PREEMPT_TOGGLE is enabled and avoids the cycle for
configurations that do not select it.
In core.c, narrow the compilation guard for the external
preempt_count_add/sub() from CONFIG_DEBUG_PREEMPT ||
CONFIG_TRACE_PREEMPT_TOGGLE to CONFIG_DEBUG_PREEMPT ||
CONFIG_PREEMPT_TRACER, since CONFIG_TRACE_PREEMPT_TOGGLE is now
handled inline.
Signed-off-by: Wander Lairson Costa <wander@redhat.com>
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
---
include/linux/preempt.h | 49 +++++++++++++++++++++++++++++++--
kernel/sched/core.c | 2 +-
kernel/trace/trace_preemptirq.c | 19 +++++++++++++
3 files changed, 66 insertions(+), 4 deletions(-)
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index d964f965c8ffc..f59a92f930d81 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -189,17 +189,60 @@ static __always_inline unsigned char interrupt_context_level(void)
*/
#define in_atomic_preempt_off() (preempt_count() != PREEMPT_DISABLE_OFFSET)
-#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_TRACE_PREEMPT_TOGGLE)
+#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)
extern void preempt_count_add(int val);
extern void preempt_count_sub(int val);
-#define preempt_count_dec_and_test() \
- ({ preempt_count_sub(1); should_resched(0); })
+#elif defined(CONFIG_TRACE_PREEMPT_TOGGLE)
+/*
+ * Avoid the circular dependency on architectures where asm/irqflags.h
+ * includes linux/preempt.h (e.g. m68k):
+ *
+ * preempt.h <--------------------+
+ * tracepoint-defs.h |
+ * static_key.h |
+ * jump_label.h |
+ * atomic.h |
+ * irqflags.h |
+ * asm/irqflags.h |
+ * preempt.h --------------+
+ */
+#include <linux/tracepoint-defs.h>
+
+extern void __trace_preempt_on(void);
+extern void __trace_preempt_off(void);
+
+DECLARE_TRACEPOINT(preempt_enable);
+DECLARE_TRACEPOINT(preempt_disable);
+
+#define __preempt_trace_enabled(type, val) \
+ (tracepoint_enabled(preempt_##type) && preempt_count() == (val))
+
+static __always_inline void preempt_count_add(int val)
+{
+ __preempt_count_add(val);
+
+ if (__preempt_trace_enabled(disable, val))
+ __trace_preempt_off();
+}
+
+static __always_inline void preempt_count_sub(int val)
+{
+ if (__preempt_trace_enabled(enable, val))
+ __trace_preempt_on();
+
+ __preempt_count_sub(val);
+}
#else
#define preempt_count_add(val) __preempt_count_add(val)
#define preempt_count_sub(val) __preempt_count_sub(val)
#define preempt_count_dec_and_test() __preempt_count_dec_and_test()
#endif
+#if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_TRACE_PREEMPT_TOGGLE)
+#define preempt_count_dec_and_test() \
+ ({ preempt_count_sub(1); should_resched(0); })
+#endif
+
#define __preempt_count_inc() __preempt_count_add(1)
#define __preempt_count_dec() __preempt_count_sub(1)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b7f77c165a6e0..125e5d71d1bd3 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5733,7 +5733,7 @@ static inline void sched_tick_stop(int cpu) { }
#endif /* !CONFIG_NO_HZ_FULL */
#if defined(CONFIG_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \
- defined(CONFIG_TRACE_PREEMPT_TOGGLE))
+ defined(CONFIG_PREEMPT_TRACER))
/*
* If the value passed in is equal to the current preempt count
* then we just disabled preemption. Start timing the latency.
diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c
index 0c42b15c38004..9f098fcb28012 100644
--- a/kernel/trace/trace_preemptirq.c
+++ b/kernel/trace/trace_preemptirq.c
@@ -115,6 +115,25 @@ NOKPROBE_SYMBOL(trace_hardirqs_off);
#ifdef CONFIG_TRACE_PREEMPT_TOGGLE
+#if !defined(CONFIG_DEBUG_PREEMPT) && !defined(CONFIG_PREEMPT_TRACER)
+EXPORT_TRACEPOINT_SYMBOL(preempt_disable);
+EXPORT_TRACEPOINT_SYMBOL(preempt_enable);
+
+void __trace_preempt_on(void)
+{
+ trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
+}
+EXPORT_SYMBOL(__trace_preempt_on);
+NOKPROBE_SYMBOL(__trace_preempt_on);
+
+void __trace_preempt_off(void)
+{
+ trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip());
+}
+EXPORT_SYMBOL(__trace_preempt_off);
+NOKPROBE_SYMBOL(__trace_preempt_off);
+#endif /* !CONFIG_DEBUG_PREEMPT */
+
void trace_preempt_on(unsigned long a0, unsigned long a1)
{
trace(preempt_enable, TP_ARGS(a0, a1));
--
2.53.0
^ permalink raw reply related
* [PATCH v3 2/4] trace/preemptirq: make TRACE_PREEMPT_TOGGLE user-selectable
From: Wander Lairson Costa @ 2026-03-11 12:50 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
Dietmar Eggemann, Steven Rostedt, Ben Segall, Mel Gorman,
Valentin Schneider, Masami Hiramatsu, Mathieu Desnoyers,
Andrew Morton, open list:SCHEDULER, open list:TRACING
Cc: acme, williams, gmonaco, Wander Lairson Costa
In-Reply-To: <20260311125021.197638-1-wander@redhat.com>
Make TRACE_PREEMPT_TOGGLE directly selectable so that
preempt_enable/preempt_disable tracepoints can be enabled in
production kernels without requiring the preemptoff latency tracer
overhead.
Signed-off-by: Wander Lairson Costa <wander@redhat.com>
---
kernel/trace/Kconfig | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 49de13cae4288..e007459ecf361 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -413,10 +413,10 @@ config STACK_TRACER
Say N if unsure.
config TRACE_PREEMPT_TOGGLE
- bool
+ bool "Preempt disable/enable tracing hooks"
help
- Enables hooks which will be called when preemption is first disabled,
- and last enabled.
+ Enables hooks into preemption disable and enable paths for
+ tracing or latency measurement.
config IRQSOFF_TRACER
bool "Interrupts-off Latency Tracer"
--
2.53.0
^ permalink raw reply related
* [PATCH v3 3/4] trace/preemptirq: add TRACE_IRQFLAGS_TOGGLE
From: Wander Lairson Costa @ 2026-03-11 12:50 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
Dietmar Eggemann, Steven Rostedt, Ben Segall, Mel Gorman,
Valentin Schneider, Masami Hiramatsu, Mathieu Desnoyers,
Andrew Morton, open list:SCHEDULER, open list:TRACING
Cc: acme, williams, gmonaco, Wander Lairson Costa
In-Reply-To: <20260311125021.197638-1-wander@redhat.com>
The IRQ disable/enable tracepoints are currently gated behind
TRACE_IRQFLAGS, a hidden config that cannot be selected directly by
users. It is only enabled when selected by PROVE_LOCKING or
IRQSOFF_TRACER, both of which carry overhead beyond what is needed
for just the tracepoints.
Introduce TRACE_IRQFLAGS_TOGGLE, a user-selectable config that enables
the irq_disable and irq_enable tracepoints independently. It is
mutually exclusive with TRACE_IRQFLAGS and mirrors how
TRACE_PREEMPT_TOGGLE works for preemption tracepoints.
Make this option depend on CONFIG_JUMP_LABEL to avoid a circular header
dependency. Without TRACE_IRQFLAGS, irqflags.h must check the static
key before invoking the tracepoint. Using tracepoint_enabled() for this
check pulls in tracepoint_defs.h, which eventually includes atomic.h
and cmpxchg.h, circling back to irqflags.h. Enforcing CONFIG_JUMP_LABEL
allows the use of static_key_false() directly, avoiding the inclusion
of the full tracepoint header chain and preventing the cycle.
Signed-off-by: Wander Lairson Costa <wander@redhat.com>
---
kernel/trace/Kconfig | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index e007459ecf361..8bea77b5f1200 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -162,7 +162,7 @@ config RING_BUFFER_ALLOW_SWAP
config PREEMPTIRQ_TRACEPOINTS
bool
- depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS
+ depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS || TRACE_IRQFLAGS_TOGGLE
select TRACING
default y
help
@@ -418,6 +418,17 @@ config TRACE_PREEMPT_TOGGLE
Enables hooks into preemption disable and enable paths for
tracing or latency measurement.
+config TRACE_IRQFLAGS_TOGGLE
+ bool "IRQ disable/enable tracing hooks"
+ default n
+ depends on TRACE_IRQFLAGS_SUPPORT && JUMP_LABEL && !TRACE_IRQFLAGS
+ help
+ Enables hooks into IRQ disable and enable paths for tracing.
+
+ This provides the irq_disable and irq_enable tracepoints
+ without pulling in the full TRACE_IRQFLAGS infrastructure
+ used by lockdep and the irqsoff latency tracer.
+
config IRQSOFF_TRACER
bool "Interrupts-off Latency Tracer"
default n
--
2.53.0
^ permalink raw reply related
* [PATCH v3 4/4] trace/preemptirq: Implement trace_irqflags hooks
From: Wander Lairson Costa @ 2026-03-11 12:50 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot,
Dietmar Eggemann, Steven Rostedt, Ben Segall, Mel Gorman,
Valentin Schneider, Masami Hiramatsu, Mathieu Desnoyers,
Andrew Morton, Wander Lairson Costa, open list, open list:TRACING
Cc: acme, williams, gmonaco
In-Reply-To: <20260311125021.197638-1-wander@redhat.com>
The previous commit introduced the CONFIG_TRACE_IRQFLAGS_TOGGLE symbol.
This patch implements the actual infrastructure to allow tracing
irq_disable and irq_enable events without pulling in the heavy
CONFIG_TRACE_IRQFLAGS dependencies like lockdep or the irqsoff tracer.
The implementation hooks into the local_irq_* macros in irqflags.h.
Instead of using the heavy trace_hardirqs_on/off calls, it uses
lightweight tracepoint_enabled() checks. If the tracepoint is enabled,
it calls into specific wrapper functions in trace_preemptirq.c.
These wrappers check the raw hardware state via raw_irqs_disabled() to
filter out redundant events, such as disabling interrupts when they
are already disabled. This approach is simpler than the full
TRACE_IRQFLAGS method which requires maintaining a per-cpu software
state variable.
To support this, the tracepoint definitions are exposed under the new
configuration. Additionally, a circular header dependency involving
irqflags.h, tracepoint-defs.h, and atomic.h is resolved by moving the
atomic.h inclusion to tracepoint.h, allowing irqflags.h to include
tracepoint-defs.h safely.
Signed-off-by: Wander Lairson Costa <wander@redhat.com>
---
include/linux/irqflags.h | 62 ++++++++++++++++++++++++++++++-
include/linux/tracepoint-defs.h | 1 -
include/linux/tracepoint.h | 1 +
include/trace/events/preemptirq.h | 2 +-
kernel/trace/trace_preemptirq.c | 49 ++++++++++++++++++++++++
5 files changed, 112 insertions(+), 3 deletions(-)
diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h
index 57b074e0cfbbb..f40557bebd325 100644
--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -18,6 +18,19 @@
#include <asm/irqflags.h>
#include <asm/percpu.h>
+/*
+ * Avoid the circular dependency
+ * irqflags.h <-----------------+
+ * tracepoint_defs.h |
+ * static_key.h |
+ * jump_label.h |
+ * atomic.h |
+ * cmpxchg.h ---------+
+ */
+#ifdef CONFIG_TRACE_IRQFLAGS_TOGGLE
+#include <linux/tracepoint-defs.h>
+#endif
+
struct task_struct;
/* Currently lockdep_softirqs_on/off is used only by lockdep */
@@ -232,7 +245,54 @@ extern void warn_bogus_irq_restore(void);
} while (0)
-#else /* !CONFIG_TRACE_IRQFLAGS */
+#elif defined(CONFIG_TRACE_IRQFLAGS_TOGGLE) /* !CONFIG_TRACE_IRQFLAGS */
+
+DECLARE_TRACEPOINT(irq_enable);
+DECLARE_TRACEPOINT(irq_disable);
+
+void trace_local_irq_enable(void);
+void trace_local_irq_disable(void);
+void trace_local_irq_save(unsigned long flags);
+void trace_local_irq_restore(unsigned long flags);
+void trace_safe_halt(void);
+
+#define local_irq_enable() \
+ do { \
+ if (tracepoint_enabled(irq_enable)) \
+ trace_local_irq_enable(); \
+ raw_local_irq_enable(); \
+ } while (0)
+
+#define local_irq_disable() \
+ do { \
+ if (tracepoint_enabled(irq_disable)) \
+ trace_local_irq_disable(); \
+ else \
+ raw_local_irq_disable(); \
+ } while (0)
+
+#define local_irq_save(flags) \
+ do { \
+ raw_local_irq_save(flags); \
+ if (tracepoint_enabled(irq_disable)) \
+ trace_local_irq_save(flags); \
+ } while (0)
+
+#define local_irq_restore(flags) \
+ do { \
+ if (tracepoint_enabled(irq_enable)) \
+ trace_local_irq_restore(flags); \
+ raw_local_irq_restore(flags); \
+ } while (0)
+
+#define safe_halt() \
+ do { \
+ if (tracepoint_enabled(irq_enable)) \
+ trace_safe_halt(); \
+ raw_safe_halt(); \
+ } while (0)
+
+#else /* !CONFIG_TRACE_IRQFLAGS_TOGGLE */
#define local_irq_enable() do { raw_local_irq_enable(); } while (0)
#define local_irq_disable() do { raw_local_irq_disable(); } while (0)
diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
index aebf0571c736e..cb1f15a4e43f0 100644
--- a/include/linux/tracepoint-defs.h
+++ b/include/linux/tracepoint-defs.h
@@ -8,7 +8,6 @@
* trace_print_flags{_u64}. Otherwise linux/tracepoint.h should be used.
*/
-#include <linux/atomic.h>
#include <linux/static_key.h>
struct static_call_key;
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 22ca1c8b54f32..e7d8c5ca00c79 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -20,6 +20,7 @@
#include <linux/rcupdate_trace.h>
#include <linux/tracepoint-defs.h>
#include <linux/static_call.h>
+#include <linux/atomic.h>
struct module;
struct tracepoint;
diff --git a/include/trace/events/preemptirq.h b/include/trace/events/preemptirq.h
index f99562d2b496b..a607a6f4e29ca 100644
--- a/include/trace/events/preemptirq.h
+++ b/include/trace/events/preemptirq.h
@@ -32,7 +32,7 @@ DECLARE_EVENT_CLASS(preemptirq_template,
(void *)((unsigned long)(_stext) + __entry->parent_offs))
);
-#ifdef CONFIG_TRACE_IRQFLAGS
+#if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_TRACE_IRQFLAGS_TOGGLE)
DEFINE_EVENT(preemptirq_template, irq_disable,
TP_PROTO(unsigned long ip, unsigned long parent_ip),
TP_ARGS(ip, parent_ip));
diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c
index 9f098fcb28012..0f32da96d2f01 100644
--- a/kernel/trace/trace_preemptirq.c
+++ b/kernel/trace/trace_preemptirq.c
@@ -111,8 +111,57 @@ void trace_hardirqs_off(void)
}
EXPORT_SYMBOL(trace_hardirqs_off);
NOKPROBE_SYMBOL(trace_hardirqs_off);
+
#endif /* CONFIG_TRACE_IRQFLAGS */
+#ifdef CONFIG_TRACE_IRQFLAGS_TOGGLE
+EXPORT_TRACEPOINT_SYMBOL(irq_disable);
+EXPORT_TRACEPOINT_SYMBOL(irq_enable);
+
+void trace_local_irq_enable(void)
+{
+ if (raw_irqs_disabled())
+ trace(irq_enable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1));
+}
+EXPORT_SYMBOL(trace_local_irq_enable);
+NOKPROBE_SYMBOL(trace_local_irq_enable);
+
+void trace_local_irq_disable(void)
+{
+ const bool was_disabled = raw_irqs_disabled();
+
+ raw_local_irq_disable();
+ if (!was_disabled)
+ trace(irq_disable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1));
+}
+EXPORT_SYMBOL(trace_local_irq_disable);
+NOKPROBE_SYMBOL(trace_local_irq_disable);
+
+void trace_local_irq_save(unsigned long flags)
+{
+ if (!raw_irqs_disabled_flags(flags))
+ trace(irq_disable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1));
+}
+EXPORT_SYMBOL(trace_local_irq_save);
+NOKPROBE_SYMBOL(trace_local_irq_save);
+
+void trace_local_irq_restore(unsigned long flags)
+{
+ if (!raw_irqs_disabled_flags(flags) && raw_irqs_disabled())
+ trace(irq_enable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1));
+}
+EXPORT_SYMBOL(trace_local_irq_restore);
+NOKPROBE_SYMBOL(trace_local_irq_restore);
+
+void trace_safe_halt(void)
+{
+ if (raw_irqs_disabled())
+ trace(irq_enable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1));
+}
+EXPORT_SYMBOL(trace_safe_halt);
+NOKPROBE_SYMBOL(trace_safe_halt);
+#endif /* CONFIG_TRACE_IRQFLAGS_TOGGLE */
+
#ifdef CONFIG_TRACE_PREEMPT_TOGGLE
#if !defined(CONFIG_DEBUG_PREEMPT) && !defined(CONFIG_PREEMPT_TRACER)
--
2.53.0
^ permalink raw reply related
* Re: [PATCH 36/61] arch/sh: Prefer IS_ERR_OR_NULL over manual NULL check
From: Geert Uytterhoeven @ 2026-03-11 13:15 UTC (permalink / raw)
To: Philipp Hahn
Cc: amd-gfx, apparmor, bpf, ceph-devel, cocci, dm-devel, dri-devel,
gfs2, intel-gfx, intel-wired-lan, iommu, kvm, linux-arm-kernel,
linux-block, linux-bluetooth, linux-btrfs, linux-cifs, linux-clk,
linux-erofs, linux-ext4, linux-fsdevel, linux-gpio, linux-hyperv,
linux-input, linux-kernel, linux-leds, linux-media, linux-mips,
linux-mm, linux-modules, linux-mtd, linux-nfs, linux-omap,
linux-phy, linux-pm, linux-rockchip, linux-s390, linux-scsi,
linux-sctp, linux-security-module, linux-sh, linux-sound,
linux-stm32, linux-trace-kernel, linux-usb, linux-wireless,
netdev, ntfs3, samba-technical, sched-ext, target-devel,
tipc-discussion, v9fs, Yoshinori Sato, Rich Felker,
John Paul Adrian Glaubitz
In-Reply-To: <20260310-b4-is_err_or_null-v1-36-bd63b656022d@avm.de>
On Tue, 10 Mar 2026 at 12:56, Philipp Hahn <phahn-oss@avm.de> wrote:
> Prefer using IS_ERR_OR_NULL() over using IS_ERR() and a manual NULL
> check.
>
> Change generated with coccinelle.
>
> To: Yoshinori Sato <ysato@users.sourceforge.jp>
> To: Rich Felker <dalias@libc.org>
> To: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
> Cc: linux-sh@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Philipp Hahn <phahn-oss@avm.de>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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