* [PATCH RT 1/8] rcutree/rcu_bh_qs: disable irq while calling rcu_preempt_qs()
2014-03-05 0:24 [PATCH RT 0/8] Linux 3.8.13.14-rt28-rc1 Steven Rostedt
@ 2014-03-05 0:24 ` Steven Rostedt
2014-03-05 0:24 ` [PATCH RT 2/8] Revert "x86: Disable IST stacks for debug/int 3/stack fault for PREEMPT_RT" Steven Rostedt
` (6 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: Steven Rostedt @ 2014-03-05 0:24 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Thomas Gleixner, Carsten Emde, Sebastian Andrzej Siewior,
John Kacur, Paul Gortmaker, stable-rt, Tiejun Chen, Bin Jiang
[-- Attachment #1: 0001-rcutree-rcu_bh_qs-disable-irq-while-calling-rcu_pree.patch --]
[-- Type: text/plain, Size: 1599 bytes --]
3.8.13.14-rt28-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: Tiejun Chen <tiejun.chen@windriver.com>
Any callers to the function rcu_preempt_qs() must disable irqs in
order to protect the assignment to ->rcu_read_unlock_special. In
RT case, rcu_bh_qs() as the wrapper of rcu_preempt_qs() is called
in some scenarios where irq is enabled, like this path,
do_single_softirq()
|
+ local_irq_enable();
+ handle_softirq()
| |
| + rcu_bh_qs()
| |
| + rcu_preempt_qs()
|
+ local_irq_disable()
So here we'd better disable irq directly inside of rcu_bh_qs() to
fix this, otherwise the kernel may be freezable sometimes as
observed. And especially this way is also kind and safe for the
potential rcu_bh_qs() usage elsewhere in the future.
Cc: stable-rt@vger.kernel.org
Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: Bin Jiang <bin.jiang@windriver.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/rcutree.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 7ec834d..6f6d133 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -186,7 +186,12 @@ static void rcu_preempt_qs(int cpu);
void rcu_bh_qs(int cpu)
{
+ unsigned long flags;
+
+ /* Callers to this function, rcu_preempt_qs(), must disable irqs. */
+ local_irq_save(flags);
rcu_preempt_qs(cpu);
+ local_irq_restore(flags);
}
#else
void rcu_bh_qs(int cpu)
--
1.8.5.3
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH RT 2/8] Revert "x86: Disable IST stacks for debug/int 3/stack fault for PREEMPT_RT"
2014-03-05 0:24 [PATCH RT 0/8] Linux 3.8.13.14-rt28-rc1 Steven Rostedt
2014-03-05 0:24 ` [PATCH RT 1/8] rcutree/rcu_bh_qs: disable irq while calling rcu_preempt_qs() Steven Rostedt
@ 2014-03-05 0:24 ` Steven Rostedt
2014-03-05 0:24 ` [PATCH RT 3/8] rt: Make cpu_chill() use hrtimer instead of msleep() Steven Rostedt
` (5 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: Steven Rostedt @ 2014-03-05 0:24 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Thomas Gleixner, Carsten Emde, Sebastian Andrzej Siewior,
John Kacur, Paul Gortmaker, stable-rt, Brian Silverman,
Andi Kleen
[-- Attachment #1: 0002-Revert-x86-Disable-IST-stacks-for-debug-int-3-stack-.patch --]
[-- Type: text/plain, Size: 4379 bytes --]
3.8.13.14-rt28-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
where do I start. Let me explain what is going on here. The code
sequence
| pushf
| pop %edx
| or $0x1,%dh
| push %edx
| mov $0xe0,%eax
| popf
| sysenter
triggers the bug. On 64bit kernel we see the double fault (with 32bit and
64bit userland) and on 32bit kernel there is no problem. The reporter said
that double fault does not happen on 64bit kernel with 64bit userland and
this is because in that case the VDSO uses the "syscall" interface instead
of "sysenter".
The bug. "popf" loads the flags with the TF bit set which enables
"single stepping" and this leads to a debug exception. Usually on 64bit
we have a special IST stack for the debug exception. Due to patch [0] we
do not use the IST stack but the kernel stack instead. On 64bit the
sysenter instruction starts in kernel with the stack address NULL. The
code sequence above enters the debug exception (TF flag) after the
sysenter instruction was executed which sets the stack pointer to NULL
and we have a fault (it seems that the debug exception saves some bytes
on the stack).
To fix the double fault I'm going to drop patch [0]. It is completely
pointless. In do_debug() and do_stack_segment() we disable preemption
which means the task can't leave the CPU. So it does not matter if we run
on IST or on kernel stack.
There is a patch [1] which drops preempt_disable() call for a 32bit
kernel but not for 64bit so there should be no regression.
And [1] seems valid even for this code sequence. We enter the debug
exception with a 256bytes long per cpu stack and migrate to the kernel
stack before calling do_debug().
[0] x86-disable-debug-stack.patch
[1] fix-rt-int3-x86_32-3.2-rt.patch
Cc: stable-rt@vger.kernel.org
Reported-by: Brian Silverman <bsilver16384@gmail.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
arch/x86/include/asm/page_64_types.h | 21 ++++++---------------
arch/x86/kernel/cpu/common.c | 2 --
arch/x86/kernel/dumpstack_64.c | 4 ----
3 files changed, 6 insertions(+), 21 deletions(-)
diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index 65b85f4..320f7bb 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -14,21 +14,12 @@
#define IRQ_STACK_ORDER 2
#define IRQ_STACK_SIZE (PAGE_SIZE << IRQ_STACK_ORDER)
-#ifdef CONFIG_PREEMPT_RT_FULL
-# define STACKFAULT_STACK 0
-# define DOUBLEFAULT_STACK 1
-# define NMI_STACK 2
-# define DEBUG_STACK 0
-# define MCE_STACK 3
-# define N_EXCEPTION_STACKS 3 /* hw limit: 7 */
-#else
-# define STACKFAULT_STACK 1
-# define DOUBLEFAULT_STACK 2
-# define NMI_STACK 3
-# define DEBUG_STACK 4
-# define MCE_STACK 5
-# define N_EXCEPTION_STACKS 5 /* hw limit: 7 */
-#endif
+#define STACKFAULT_STACK 1
+#define DOUBLEFAULT_STACK 2
+#define NMI_STACK 3
+#define DEBUG_STACK 4
+#define MCE_STACK 5
+#define N_EXCEPTION_STACKS 5 /* hw limit: 7 */
#define PUD_PAGE_SIZE (_AC(1, UL) << PUD_SHIFT)
#define PUD_PAGE_MASK (~(PUD_PAGE_SIZE-1))
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 2636e0f..9c3ab43 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1103,9 +1103,7 @@ DEFINE_PER_CPU(struct task_struct *, fpu_owner_task);
*/
static const unsigned int exception_stack_sizes[N_EXCEPTION_STACKS] = {
[0 ... N_EXCEPTION_STACKS - 1] = EXCEPTION_STKSZ,
-#if DEBUG_STACK > 0
[DEBUG_STACK - 1] = DEBUG_STKSZ
-#endif
};
static DEFINE_PER_CPU_PAGE_ALIGNED(char, exception_stacks
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index f16c07b..b653675 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -21,14 +21,10 @@
(N_EXCEPTION_STACKS + DEBUG_STKSZ/EXCEPTION_STKSZ - 2)
static char x86_stack_ids[][8] = {
-#if DEBUG_STACK > 0
[ DEBUG_STACK-1 ] = "#DB",
-#endif
[ NMI_STACK-1 ] = "NMI",
[ DOUBLEFAULT_STACK-1 ] = "#DF",
-#if STACKFAULT_STACK > 0
[ STACKFAULT_STACK-1 ] = "#SS",
-#endif
[ MCE_STACK-1 ] = "#MC",
#if DEBUG_STKSZ > EXCEPTION_STKSZ
[ N_EXCEPTION_STACKS ...
--
1.8.5.3
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH RT 3/8] rt: Make cpu_chill() use hrtimer instead of msleep()
2014-03-05 0:24 [PATCH RT 0/8] Linux 3.8.13.14-rt28-rc1 Steven Rostedt
2014-03-05 0:24 ` [PATCH RT 1/8] rcutree/rcu_bh_qs: disable irq while calling rcu_preempt_qs() Steven Rostedt
2014-03-05 0:24 ` [PATCH RT 2/8] Revert "x86: Disable IST stacks for debug/int 3/stack fault for PREEMPT_RT" Steven Rostedt
@ 2014-03-05 0:24 ` Steven Rostedt
2014-03-05 0:24 ` [PATCH RT 4/8] kernel/hrtimer: be non-freezeable in cpu_chill() Steven Rostedt
` (4 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: Steven Rostedt @ 2014-03-05 0:24 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Thomas Gleixner, Carsten Emde, Sebastian Andrzej Siewior,
John Kacur, Paul Gortmaker, stable-rt
[-- Attachment #1: 0003-rt-Make-cpu_chill-use-hrtimer-instead-of-msleep.patch --]
[-- Type: text/plain, Size: 3762 bytes --]
3.8.13.14-rt28-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: Steven Rostedt <rostedt@goodmis.org>
Ulrich Obergfell pointed out that cpu_chill() calls msleep() which is woken
up by the ksoftirqd running the TIMER softirq. But as the cpu_chill() is
called from softirq context, it may block the ksoftirqd() from running, in
which case, it may never wake up the msleep() causing the deadlock.
I checked the vmcore, and irq/74-qla2xxx is stuck in the msleep() call,
running on CPU 8. The one ksoftirqd that is stuck, happens to be the one that
runs on CPU 8, and it is blocked on a lock held by irq/74-qla2xxx. As that
ksoftirqd is the one that will wake up irq/74-qla2xxx, and it happens to be
blocked on a lock that irq/74-qla2xxx holds, we have our deadlock.
The solution is not to convert the cpu_chill() back to a cpu_relax() as that
will re-create a possible live lock that the cpu_chill() fixed earlier, and may
also leave this bug open on other softirqs. The fix is to remove the
dependency on ksoftirqd from cpu_chill(). That is, instead of calling
msleep() that requires ksoftirqd to wake it up, use the
hrtimer_nanosleep() code that does the wakeup from hard irq context.
|Looks to be the lock of the block softirq. I don't have the core dump
|anymore, but from what I could tell the ksoftirqd was blocked on the
|block softirq lock, where the block softirq handler did a msleep
|(called by the qla2xxx interrupt handler).
|
|Looking at trigger_softirq() in block/blk-softirq.c, it can do a
|smp_callfunction() to another cpu to run the block softirq. If that
|happens to be the cpu where the qla2xx irq handler is doing the block
|softirq and is in a middle of a msleep(), I believe the ksoftirqd will
|try to run the softirq. If it does that, then BOOM, it's deadlocked
|because the ksoftirqd will never run the timer softirq either.
|I should have also stated that it was only one lock that was involved.
|But the lock owner was doing a msleep() that requires a wakeup by
|ksoftirqd to continue. If ksoftirqd happens to be blocked on a lock
|held by the msleep() caller, then you have your deadlock.
|
|It's best not to have any softirqs going to sleep requiring another
|softirq to wake it up. Note, if we ever require a timer softirq to do a
|cpu_chill() it will most definitely hit this deadlock.
Cc: stable-rt@vger.kernel.org
Found-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
[bigeasy: add the 4 | chapters from email]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
include/linux/delay.h | 2 +-
kernel/hrtimer.c | 15 +++++++++++++++
2 files changed, 16 insertions(+), 1 deletion(-)
diff --git a/include/linux/delay.h b/include/linux/delay.h
index e23a7c0..37caab3 100644
--- a/include/linux/delay.h
+++ b/include/linux/delay.h
@@ -53,7 +53,7 @@ static inline void ssleep(unsigned int seconds)
}
#ifdef CONFIG_PREEMPT_RT_FULL
-# define cpu_chill() msleep(1)
+extern void cpu_chill(void);
#else
# define cpu_chill() cpu_relax()
#endif
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index aa5eb4f..2f023aa 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1852,6 +1852,21 @@ SYSCALL_DEFINE2(nanosleep, struct timespec __user *, rqtp,
return hrtimer_nanosleep(&tu, rmtp, HRTIMER_MODE_REL, CLOCK_MONOTONIC);
}
+#ifdef CONFIG_PREEMPT_RT_FULL
+/*
+ * Sleep for 1 ms in hope whoever holds what we want will let it go.
+ */
+void cpu_chill(void)
+{
+ struct timespec tu = {
+ .tv_nsec = NSEC_PER_MSEC,
+ };
+
+ hrtimer_nanosleep(&tu, NULL, HRTIMER_MODE_REL, CLOCK_MONOTONIC);
+}
+EXPORT_SYMBOL(cpu_chill);
+#endif
+
/*
* Functions related to boot-time initialization:
*/
--
1.8.5.3
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH RT 4/8] kernel/hrtimer: be non-freezeable in cpu_chill()
2014-03-05 0:24 [PATCH RT 0/8] Linux 3.8.13.14-rt28-rc1 Steven Rostedt
` (2 preceding siblings ...)
2014-03-05 0:24 ` [PATCH RT 3/8] rt: Make cpu_chill() use hrtimer instead of msleep() Steven Rostedt
@ 2014-03-05 0:24 ` Steven Rostedt
2014-03-05 0:24 ` [PATCH RT 5/8] arm/unwind: use a raw_spin_lock Steven Rostedt
` (3 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: Steven Rostedt @ 2014-03-05 0:24 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Thomas Gleixner, Carsten Emde, Sebastian Andrzej Siewior,
John Kacur, Paul Gortmaker, stable-rt
[-- Attachment #1: 0004-kernel-hrtimer-be-non-freezeable-in-cpu_chill.patch --]
[-- Type: text/plain, Size: 2390 bytes --]
3.8.13.14-rt28-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Since we replaced msleep() by hrtimer I see now and then (rarely) this:
| [....] Waiting for /dev to be fully populated...
| =====================================
| [ BUG: udevd/229 still has locks held! ]
| 3.12.11-rt17 #23 Not tainted
| -------------------------------------
| 1 lock held by udevd/229:
| #0: (&type->i_mutex_dir_key#2){+.+.+.}, at: lookup_slow+0x28/0x98
|
| stack backtrace:
| CPU: 0 PID: 229 Comm: udevd Not tainted 3.12.11-rt17 #23
| (unwind_backtrace+0x0/0xf8) from (show_stack+0x10/0x14)
| (show_stack+0x10/0x14) from (dump_stack+0x74/0xbc)
| (dump_stack+0x74/0xbc) from (do_nanosleep+0x120/0x160)
| (do_nanosleep+0x120/0x160) from (hrtimer_nanosleep+0x90/0x110)
| (hrtimer_nanosleep+0x90/0x110) from (cpu_chill+0x30/0x38)
| (cpu_chill+0x30/0x38) from (dentry_kill+0x158/0x1ec)
| (dentry_kill+0x158/0x1ec) from (dput+0x74/0x15c)
| (dput+0x74/0x15c) from (lookup_real+0x4c/0x50)
| (lookup_real+0x4c/0x50) from (__lookup_hash+0x34/0x44)
| (__lookup_hash+0x34/0x44) from (lookup_slow+0x38/0x98)
| (lookup_slow+0x38/0x98) from (path_lookupat+0x208/0x7fc)
| (path_lookupat+0x208/0x7fc) from (filename_lookup+0x20/0x60)
| (filename_lookup+0x20/0x60) from (user_path_at_empty+0x50/0x7c)
| (user_path_at_empty+0x50/0x7c) from (user_path_at+0x14/0x1c)
| (user_path_at+0x14/0x1c) from (vfs_fstatat+0x48/0x94)
| (vfs_fstatat+0x48/0x94) from (SyS_stat64+0x14/0x30)
| (SyS_stat64+0x14/0x30) from (ret_fast_syscall+0x0/0x48)
For now I see no better way but to disable the freezer the sleep the period.
Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/hrtimer.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 2f023aa..2e66fbb 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1861,8 +1861,12 @@ void cpu_chill(void)
struct timespec tu = {
.tv_nsec = NSEC_PER_MSEC,
};
+ unsigned int freeze_flag = current->flags & PF_NOFREEZE;
+ current->flags |= PF_NOFREEZE;
hrtimer_nanosleep(&tu, NULL, HRTIMER_MODE_REL, CLOCK_MONOTONIC);
+ if (!freeze_flag)
+ current->flags &= ~PF_NOFREEZE;
}
EXPORT_SYMBOL(cpu_chill);
#endif
--
1.8.5.3
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH RT 5/8] arm/unwind: use a raw_spin_lock
2014-03-05 0:24 [PATCH RT 0/8] Linux 3.8.13.14-rt28-rc1 Steven Rostedt
` (3 preceding siblings ...)
2014-03-05 0:24 ` [PATCH RT 4/8] kernel/hrtimer: be non-freezeable in cpu_chill() Steven Rostedt
@ 2014-03-05 0:24 ` Steven Rostedt
2014-03-05 0:24 ` [PATCH RT 6/8] net: ip_send_unicast_reply: add missing local serialization Steven Rostedt
` (2 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: Steven Rostedt @ 2014-03-05 0:24 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Thomas Gleixner, Carsten Emde, Sebastian Andrzej Siewior,
John Kacur, Paul Gortmaker, stable-rt
[-- Attachment #1: 0005-arm-unwind-use-a-raw_spin_lock.patch --]
[-- Type: text/plain, Size: 2884 bytes --]
3.8.13.14-rt28-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Mostly unwind is done with irqs enabled however SLUB may call it with
irqs disabled while creating a new SLUB cache.
I had system freeze while loading a module which called
kmem_cache_create() on init. That means SLUB's __slab_alloc() disabled
interrupts and then
->new_slab_objects()
->new_slab()
->setup_object()
->setup_object_debug()
->init_tracking()
->set_track()
->save_stack_trace()
->save_stack_trace_tsk()
->walk_stackframe()
->unwind_frame()
->unwind_find_idx()
=>spin_lock_irqsave(&unwind_lock);
Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
arch/arm/kernel/unwind.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
index 00df012..bbafc67 100644
--- a/arch/arm/kernel/unwind.c
+++ b/arch/arm/kernel/unwind.c
@@ -87,7 +87,7 @@ extern const struct unwind_idx __start_unwind_idx[];
static const struct unwind_idx *__origin_unwind_idx;
extern const struct unwind_idx __stop_unwind_idx[];
-static DEFINE_SPINLOCK(unwind_lock);
+static DEFINE_RAW_SPINLOCK(unwind_lock);
static LIST_HEAD(unwind_tables);
/* Convert a prel31 symbol to an absolute address */
@@ -195,7 +195,7 @@ static const struct unwind_idx *unwind_find_idx(unsigned long addr)
/* module unwind tables */
struct unwind_table *table;
- spin_lock_irqsave(&unwind_lock, flags);
+ raw_spin_lock_irqsave(&unwind_lock, flags);
list_for_each_entry(table, &unwind_tables, list) {
if (addr >= table->begin_addr &&
addr < table->end_addr) {
@@ -207,7 +207,7 @@ static const struct unwind_idx *unwind_find_idx(unsigned long addr)
break;
}
}
- spin_unlock_irqrestore(&unwind_lock, flags);
+ raw_spin_unlock_irqrestore(&unwind_lock, flags);
}
pr_debug("%s: idx = %p\n", __func__, idx);
@@ -469,9 +469,9 @@ struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
tab->begin_addr = text_addr;
tab->end_addr = text_addr + text_size;
- spin_lock_irqsave(&unwind_lock, flags);
+ raw_spin_lock_irqsave(&unwind_lock, flags);
list_add_tail(&tab->list, &unwind_tables);
- spin_unlock_irqrestore(&unwind_lock, flags);
+ raw_spin_unlock_irqrestore(&unwind_lock, flags);
return tab;
}
@@ -483,9 +483,9 @@ void unwind_table_del(struct unwind_table *tab)
if (!tab)
return;
- spin_lock_irqsave(&unwind_lock, flags);
+ raw_spin_lock_irqsave(&unwind_lock, flags);
list_del(&tab->list);
- spin_unlock_irqrestore(&unwind_lock, flags);
+ raw_spin_unlock_irqrestore(&unwind_lock, flags);
kfree(tab);
}
--
1.8.5.3
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH RT 6/8] net: ip_send_unicast_reply: add missing local serialization
2014-03-05 0:24 [PATCH RT 0/8] Linux 3.8.13.14-rt28-rc1 Steven Rostedt
` (4 preceding siblings ...)
2014-03-05 0:24 ` [PATCH RT 5/8] arm/unwind: use a raw_spin_lock Steven Rostedt
@ 2014-03-05 0:24 ` Steven Rostedt
2014-03-05 0:24 ` [PATCH RT 7/8] rcu: Eliminate softirq processing from rcutree Steven Rostedt
2014-03-05 0:24 ` [PATCH RT 8/8] Linux 3.8.13.14-rt28-rc1 Steven Rostedt
7 siblings, 0 replies; 9+ messages in thread
From: Steven Rostedt @ 2014-03-05 0:24 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Thomas Gleixner, Carsten Emde, Sebastian Andrzej Siewior,
John Kacur, Paul Gortmaker, stable-rt, Nicholas Mc Guire
[-- Attachment #1: 0006-net-ip_send_unicast_reply-add-missing-local-serializ.patch --]
[-- Type: text/plain, Size: 3662 bytes --]
3.8.13.14-rt28-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: Nicholas Mc Guire <der.herr@hofr.at>
in response to the oops in ip_output.c:ip_send_unicast_reply under high
network load with CONFIG_PREEMPT_RT_FULL=y, reported by Sami Pietikainen
<Sami.Pietikainen@wapice.com>, this patch adds local serialization in
ip_send_unicast_reply.
from ip_output.c:
/*
* Generic function to send a packet as reply to another packet.
* Used to send some TCP resets/acks so far.
*
* Use a fake percpu inet socket to avoid false sharing and contention.
*/
static DEFINE_PER_CPU(struct inet_sock, unicast_sock) = {
...
which was added in commit be9f4a44 in linux-stable. The git log, wich
introduced the PER_CPU unicast_sock, states:
<snip>
commit be9f4a44e7d41cee50ddb5f038fc2391cbbb4046
Author: Eric Dumazet <edumazet@google.com>
Date: Thu Jul 19 07:34:03 2012 +0000
ipv4: tcp: remove per net tcp_sock
tcp_v4_send_reset() and tcp_v4_send_ack() use a single socket
per network namespace.
This leads to bad behavior on multiqueue NICS, because many cpus
contend for the socket lock and once socket lock is acquired, extra
false sharing on various socket fields slow down the operations.
To better resist to attacks, we use a percpu socket. Each cpu can
run without contention, using appropriate memory (local node)
<snip>
The per-cpu here thus is assuming exclusivity serializing per cpu - so
the use of get_cpu_ligh introduced in
net-use-cpu-light-in-ip-send-unicast-reply.patch, which droped the
preempt_disable in favor of a migrate_disable is probably wrong as this
only handles the referencial consistency but not the serialization. To
evade a preempt_disable here a local lock would be needed.
Therapie:
* add local lock:
* and re-introduce local serialization:
Tested on x86 with high network load using the testcase from Sami Pietikainen
while : ; do wget -O - ftp://LOCAL_SERVER/empty_file > /dev/null 2>&1; done
Link: http://www.spinics.net/lists/linux-rt-users/msg11007.html
Cc: stable-rt@vger.kernel.org
Signed-off-by: Nicholas Mc Guire <der.herr@hofr.at>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
net/ipv4/ip_output.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 90af992..6e75fb1 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -79,6 +79,7 @@
#include <linux/mroute.h>
#include <linux/netlink.h>
#include <linux/tcp.h>
+#include <linux/locallock.h>
int sysctl_ip_default_ttl __read_mostly = IPDEFTTL;
EXPORT_SYMBOL(sysctl_ip_default_ttl);
@@ -1471,6 +1472,9 @@ static DEFINE_PER_CPU(struct inet_sock, unicast_sock) = {
.uc_ttl = -1,
};
+/* serialize concurrent calls on the same CPU to ip_send_unicast_reply */
+static DEFINE_LOCAL_IRQ_LOCK(unicast_lock);
+
void ip_send_unicast_reply(struct net *net, struct sk_buff *skb, __be32 daddr,
__be32 saddr, const struct ip_reply_arg *arg,
unsigned int len)
@@ -1508,8 +1512,7 @@ void ip_send_unicast_reply(struct net *net, struct sk_buff *skb, __be32 daddr,
if (IS_ERR(rt))
return;
- get_cpu_light();
- inet = &__get_cpu_var(unicast_sock);
+ inet = &get_locked_var(unicast_lock, unicast_sock);
inet->tos = arg->tos;
sk = &inet->sk;
@@ -1533,7 +1536,7 @@ void ip_send_unicast_reply(struct net *net, struct sk_buff *skb, __be32 daddr,
ip_push_pending_frames(sk, &fl4);
}
- put_cpu_light();
+ put_locked_var(unicast_lock, unicast_sock);
ip_rt_put(rt);
}
--
1.8.5.3
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH RT 7/8] rcu: Eliminate softirq processing from rcutree
2014-03-05 0:24 [PATCH RT 0/8] Linux 3.8.13.14-rt28-rc1 Steven Rostedt
` (5 preceding siblings ...)
2014-03-05 0:24 ` [PATCH RT 6/8] net: ip_send_unicast_reply: add missing local serialization Steven Rostedt
@ 2014-03-05 0:24 ` Steven Rostedt
2014-03-05 0:24 ` [PATCH RT 8/8] Linux 3.8.13.14-rt28-rc1 Steven Rostedt
7 siblings, 0 replies; 9+ messages in thread
From: Steven Rostedt @ 2014-03-05 0:24 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Thomas Gleixner, Carsten Emde, Sebastian Andrzej Siewior,
John Kacur, Paul Gortmaker, stable-rt, Mike Galbraith,
Paul E. McKenney
[-- Attachment #1: 0007-rcu-Eliminate-softirq-processing-from-rcutree.patch --]
[-- Type: text/plain, Size: 12390 bytes --]
3.8.13.14-rt28-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Running RCU out of softirq is a problem for some workloads that would
like to manage RCU core processing independently of other softirq work,
for example, setting kthread priority. This commit therefore moves the
RCU core work from softirq to a per-CPU/per-flavor SCHED_OTHER kthread
named rcuc. The SCHED_OTHER approach avoids the scalability problems
that appeared with the earlier attempt to move RCU core processing to
from softirq to kthreads. That said, kernels built with RCU_BOOST=y
will run the rcuc kthreads at the RCU-boosting priority.
Cc: stable-rt@vger.kernel.org
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Mike Galbraith <bitbucket@online.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/rcutree.c | 114 ++++++++++++++++++++++++++++++++++++-----
kernel/rcutree.h | 3 +-
kernel/rcutree_plugin.h | 133 +++++-------------------------------------------
3 files changed, 114 insertions(+), 136 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 6f6d133..6a34f87 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -53,6 +53,11 @@
#include <linux/delay.h>
#include <linux/stop_machine.h>
#include <linux/random.h>
+#include <linux/delay.h>
+#include <linux/gfp.h>
+#include <linux/oom.h>
+#include <linux/smpboot.h>
+#include "time/tick-internal.h"
#include "rcutree.h"
#include <trace/events/rcu.h>
@@ -127,8 +132,6 @@ EXPORT_SYMBOL_GPL(rcu_scheduler_active);
*/
static int rcu_scheduler_fully_active __read_mostly;
-#ifdef CONFIG_RCU_BOOST
-
/*
* Control variables for per-CPU and per-rcu_node kthreads. These
* handle all flavors of RCU.
@@ -138,8 +141,6 @@ DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
DEFINE_PER_CPU(char, rcu_cpu_has_work);
-#endif /* #ifdef CONFIG_RCU_BOOST */
-
static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
static void invoke_rcu_core(void);
static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
@@ -2048,16 +2049,14 @@ __rcu_process_callbacks(struct rcu_state *rsp)
/*
* Do RCU core processing for the current CPU.
*/
-static void rcu_process_callbacks(struct softirq_action *unused)
+static void rcu_process_callbacks(void)
{
struct rcu_state *rsp;
if (cpu_is_offline(smp_processor_id()))
return;
- trace_rcu_utilization("Start RCU core");
for_each_rcu_flavor(rsp)
__rcu_process_callbacks(rsp);
- trace_rcu_utilization("End RCU core");
}
/*
@@ -2071,17 +2070,105 @@ static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
{
if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active)))
return;
- if (likely(!rsp->boost)) {
- rcu_do_batch(rsp, rdp);
- return;
- }
- invoke_rcu_callbacks_kthread();
+ rcu_do_batch(rsp, rdp);
}
+static void rcu_wake_cond(struct task_struct *t, int status)
+{
+ /*
+ * If the thread is yielding, only wake it when this
+ * is invoked from idle
+ */
+ if (t && (status != RCU_KTHREAD_YIELDING || is_idle_task(current)))
+ wake_up_process(t);
+}
+
+/*
+ * Wake up this CPU's rcuc kthread to do RCU core processing.
+ */
static void invoke_rcu_core(void)
{
- raise_softirq(RCU_SOFTIRQ);
+ unsigned long flags;
+ struct task_struct *t;
+
+ if (!cpu_online(smp_processor_id()))
+ return;
+ local_irq_save(flags);
+ __this_cpu_write(rcu_cpu_has_work, 1);
+ t = __this_cpu_read(rcu_cpu_kthread_task);
+ if (t != NULL && current != t)
+ rcu_wake_cond(t, __this_cpu_read(rcu_cpu_kthread_status));
+ local_irq_restore(flags);
+}
+
+static void rcu_cpu_kthread_park(unsigned int cpu)
+{
+ per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU;
+}
+
+static int rcu_cpu_kthread_should_run(unsigned int cpu)
+{
+ return __this_cpu_read(rcu_cpu_has_work);
+}
+
+/*
+ * Per-CPU kernel thread that invokes RCU callbacks. This replaces the
+ * RCU softirq used in flavors and configurations of RCU that do not
+ * support RCU priority boosting.
+ */
+static void rcu_cpu_kthread(unsigned int cpu)
+{
+ unsigned int *statusp = &__get_cpu_var(rcu_cpu_kthread_status);
+ char work, *workp = &__get_cpu_var(rcu_cpu_has_work);
+ int spincnt;
+
+ for (spincnt = 0; spincnt < 10; spincnt++) {
+ trace_rcu_utilization("Start CPU kthread@rcu_wait");
+ local_bh_disable();
+ *statusp = RCU_KTHREAD_RUNNING;
+ this_cpu_inc(rcu_cpu_kthread_loops);
+ local_irq_disable();
+ work = *workp;
+ *workp = 0;
+ local_irq_enable();
+ if (work)
+ rcu_process_callbacks();
+ local_bh_enable();
+ if (*workp == 0) {
+ trace_rcu_utilization("End CPU kthread@rcu_wait");
+ *statusp = RCU_KTHREAD_WAITING;
+ return;
+ }
+ }
+ *statusp = RCU_KTHREAD_YIELDING;
+ trace_rcu_utilization("Start CPU kthread@rcu_yield");
+ schedule_timeout_interruptible(2);
+ trace_rcu_utilization("End CPU kthread@rcu_yield");
+ *statusp = RCU_KTHREAD_WAITING;
+}
+
+static struct smp_hotplug_thread rcu_cpu_thread_spec = {
+ .store = &rcu_cpu_kthread_task,
+ .thread_should_run = rcu_cpu_kthread_should_run,
+ .thread_fn = rcu_cpu_kthread,
+ .thread_comm = "rcuc/%u",
+ .setup = rcu_cpu_kthread_setup,
+ .park = rcu_cpu_kthread_park,
+};
+
+/*
+ * Spawn per-CPU RCU core processing kthreads.
+ */
+static int __init rcu_spawn_core_kthreads(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu)
+ per_cpu(rcu_cpu_has_work, cpu) = 0;
+ BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec));
+ return 0;
}
+early_initcall(rcu_spawn_core_kthreads);
/*
* Handle any core-RCU processing required by a call_rcu() invocation.
@@ -3087,7 +3174,6 @@ void __init rcu_init(void)
rcu_init_one(&rcu_bh_state, &rcu_bh_data);
__rcu_init_preempt();
rcu_init_nocb();
- open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
/*
* We don't need protection against CPU-hotplug here because
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 5cfdff9..d67eaed 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -519,10 +519,9 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
static void __init __rcu_init_preempt(void);
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
-static void invoke_rcu_callbacks_kthread(void);
static bool rcu_is_callbacks_kthread(void);
+static void rcu_cpu_kthread_setup(unsigned int cpu);
#ifdef CONFIG_RCU_BOOST
-static void rcu_preempt_do_callbacks(void);
static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
struct rcu_node *rnp);
#endif /* #ifdef CONFIG_RCU_BOOST */
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 778f138..a24ee9f 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -24,11 +24,6 @@
* Paul E. McKenney <paulmck@linux.vnet.ibm.com>
*/
-#include <linux/delay.h>
-#include <linux/gfp.h>
-#include <linux/oom.h>
-#include <linux/smpboot.h>
-
#define RCU_KTHREAD_PRIO 1
#ifdef CONFIG_RCU_BOOST
@@ -648,15 +643,6 @@ static void rcu_preempt_check_callbacks(int cpu)
t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS;
}
-#ifdef CONFIG_RCU_BOOST
-
-static void rcu_preempt_do_callbacks(void)
-{
- rcu_do_batch(&rcu_preempt_state, &__get_cpu_var(rcu_preempt_data));
-}
-
-#endif /* #ifdef CONFIG_RCU_BOOST */
-
/*
* Queue a preemptible-RCU callback for invocation after a grace period.
*/
@@ -1092,6 +1078,19 @@ static void __init __rcu_init_preempt(void)
#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
+/*
+ * If boosting, set rcuc kthreads to realtime priority.
+ */
+static void rcu_cpu_kthread_setup(unsigned int cpu)
+{
+#ifdef CONFIG_RCU_BOOST
+ struct sched_param sp;
+
+ sp.sched_priority = RCU_KTHREAD_PRIO;
+ sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
+#endif /* #ifdef CONFIG_RCU_BOOST */
+}
+
#ifdef CONFIG_RCU_BOOST
#include "rtmutex_common.h"
@@ -1123,16 +1122,6 @@ static void rcu_initiate_boost_trace(struct rcu_node *rnp)
#endif /* #else #ifdef CONFIG_RCU_TRACE */
-static void rcu_wake_cond(struct task_struct *t, int status)
-{
- /*
- * If the thread is yielding, only wake it when this
- * is invoked from idle
- */
- if (status != RCU_KTHREAD_YIELDING || is_idle_task(current))
- wake_up_process(t);
-}
-
/*
* Carry out RCU priority boosting on the task indicated by ->exp_tasks
* or ->boost_tasks, advancing the pointer to the next task in the
@@ -1276,23 +1265,6 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
}
/*
- * Wake up the per-CPU kthread to invoke RCU callbacks.
- */
-static void invoke_rcu_callbacks_kthread(void)
-{
- unsigned long flags;
-
- local_irq_save(flags);
- __this_cpu_write(rcu_cpu_has_work, 1);
- if (__this_cpu_read(rcu_cpu_kthread_task) != NULL &&
- current != __this_cpu_read(rcu_cpu_kthread_task)) {
- rcu_wake_cond(__this_cpu_read(rcu_cpu_kthread_task),
- __this_cpu_read(rcu_cpu_kthread_status));
- }
- local_irq_restore(flags);
-}
-
-/*
* Is the current CPU running the RCU-callbacks kthread?
* Caller must have preemption disabled.
*/
@@ -1346,67 +1318,6 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
return 0;
}
-static void rcu_kthread_do_work(void)
-{
- rcu_do_batch(&rcu_sched_state, &__get_cpu_var(rcu_sched_data));
- rcu_do_batch(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
- rcu_preempt_do_callbacks();
-}
-
-static void rcu_cpu_kthread_setup(unsigned int cpu)
-{
- struct sched_param sp;
-
- sp.sched_priority = RCU_KTHREAD_PRIO;
- sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
-}
-
-static void rcu_cpu_kthread_park(unsigned int cpu)
-{
- per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU;
-}
-
-static int rcu_cpu_kthread_should_run(unsigned int cpu)
-{
- return __get_cpu_var(rcu_cpu_has_work);
-}
-
-/*
- * Per-CPU kernel thread that invokes RCU callbacks. This replaces the
- * RCU softirq used in flavors and configurations of RCU that do not
- * support RCU priority boosting.
- */
-static void rcu_cpu_kthread(unsigned int cpu)
-{
- unsigned int *statusp = &__get_cpu_var(rcu_cpu_kthread_status);
- char work, *workp = &__get_cpu_var(rcu_cpu_has_work);
- int spincnt;
-
- for (spincnt = 0; spincnt < 10; spincnt++) {
- trace_rcu_utilization("Start CPU kthread@rcu_wait");
- local_bh_disable();
- *statusp = RCU_KTHREAD_RUNNING;
- this_cpu_inc(rcu_cpu_kthread_loops);
- local_irq_disable();
- work = *workp;
- *workp = 0;
- local_irq_enable();
- if (work)
- rcu_kthread_do_work();
- local_bh_enable();
- if (*workp == 0) {
- trace_rcu_utilization("End CPU kthread@rcu_wait");
- *statusp = RCU_KTHREAD_WAITING;
- return;
- }
- }
- *statusp = RCU_KTHREAD_YIELDING;
- trace_rcu_utilization("Start CPU kthread@rcu_yield");
- schedule_timeout_interruptible(2);
- trace_rcu_utilization("End CPU kthread@rcu_yield");
- *statusp = RCU_KTHREAD_WAITING;
-}
-
/*
* Set the per-rcu_node kthread's affinity to cover all CPUs that are
* served by the rcu_node in question. The CPU hotplug lock is still
@@ -1440,27 +1351,14 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
free_cpumask_var(cm);
}
-static struct smp_hotplug_thread rcu_cpu_thread_spec = {
- .store = &rcu_cpu_kthread_task,
- .thread_should_run = rcu_cpu_kthread_should_run,
- .thread_fn = rcu_cpu_kthread,
- .thread_comm = "rcuc/%u",
- .setup = rcu_cpu_kthread_setup,
- .park = rcu_cpu_kthread_park,
-};
-
/*
* Spawn all kthreads -- called as soon as the scheduler is running.
*/
static int __init rcu_spawn_kthreads(void)
{
struct rcu_node *rnp;
- int cpu;
rcu_scheduler_fully_active = 1;
- for_each_possible_cpu(cpu)
- per_cpu(rcu_cpu_has_work, cpu) = 0;
- BUG_ON(smpboot_register_percpu_thread(&rcu_cpu_thread_spec));
rnp = rcu_get_root(rcu_state);
(void)rcu_spawn_one_boost_kthread(rcu_state, rnp);
if (NUM_RCU_NODES > 1) {
@@ -1488,11 +1386,6 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
-static void invoke_rcu_callbacks_kthread(void)
-{
- WARN_ON_ONCE(1);
-}
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH RT 8/8] Linux 3.8.13.14-rt28-rc1
2014-03-05 0:24 [PATCH RT 0/8] Linux 3.8.13.14-rt28-rc1 Steven Rostedt
` (6 preceding siblings ...)
2014-03-05 0:24 ` [PATCH RT 7/8] rcu: Eliminate softirq processing from rcutree Steven Rostedt
@ 2014-03-05 0:24 ` Steven Rostedt
7 siblings, 0 replies; 9+ messages in thread
From: Steven Rostedt @ 2014-03-05 0:24 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Thomas Gleixner, Carsten Emde, Sebastian Andrzej Siewior,
John Kacur, Paul Gortmaker
[-- Attachment #1: 0008-Linux-3.8.13.14-rt28-rc1.patch --]
[-- Type: text/plain, Size: 408 bytes --]
3.8.13.14-rt28-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
---
localversion-rt | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/localversion-rt b/localversion-rt
index be1e37b..124baf7 100644
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt27
+-rt28-rc1
--
1.8.5.3
^ permalink raw reply related [flat|nested] 9+ messages in thread