[PATCH v5 06/18] add_timer_on(): Make sure callers have TIMER_PINNED flag

Anna-Maria Behnsen
2023-03-01T14:18:35Z

The implementation of the hierachical timer pull model will change the
timer bases per CPU. Timers, that have to expire on a specific CPU, require
the TIMER_PINNED flag. Otherwise they will be queued on the dedicated CPU
but in global timer base and those timers could also expire on other
CPUs. Timers with TIMER_DEFERRABLE flag end up in a separate base anyway
and are executed on the local CPU only.

Therefore add the missing TIMER_PINNED flag for those callers who use
add_timer_on() without the flag. No functional change.

Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: John Stultz <jstultz@google.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
---
v5: Add comment in workqueue.c that it's only a workaround for now
---
arch/x86/kernel/tsc_sync.c | 3 ++-
drivers/char/random.c | 2 +-
kernel/time/clocksource.c | 2 +-
kernel/workqueue.c | 15 +++++++++++++--
4 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c
index 9452dc9664b5..eab827288e0f 100644
--- a/arch/x86/kernel/tsc_sync.c
+++ b/arch/x86/kernel/tsc_sync.c
@@ -110,7 +110,8 @@ static int __init start_sync_check_timer(void)
if (!cpu_feature_enabled(X86_FEATURE_TSC_ADJUST) || tsc_clocksource_reliable)
return 0;

- timer_setup(&tsc_sync_check_timer, tsc_sync_check_timer_fn, 0);
+ timer_setup(&tsc_sync_check_timer, tsc_sync_check_timer_fn,
+ TIMER_PINNED);
tsc_sync_check_timer.expires = jiffies + SYNC_CHECK_INTERVAL;
add_timer(&tsc_sync_check_timer);

diff --git a/drivers/char/random.c b/drivers/char/random.c
index ce3ccd172cc8..db6a7c0695de 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1007,7 +1007,7 @@ static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = {
#define FASTMIX_PERM HSIPHASH_PERMUTATION
.pool = { HSIPHASH_CONST_0, HSIPHASH_CONST_1, HSIPHASH_CONST_2, HSIPHASH_CONST_3 },
#endif
- .mix = __TIMER_INITIALIZER(mix_interrupt_randomness, 0)
+ .mix = __TIMER_INITIALIZER(mix_interrupt_randomness, TIMER_PINNED)
};

/*
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 91836b727cef..e982c119e3c9 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -561,7 +561,7 @@ static inline void clocksource_start_watchdog(void)
{
if (watchdog_running || !watchdog || list_empty(&watchdog_list))
return;
- timer_setup(&watchdog_timer, clocksource_watchdog, 0);
+ timer_setup(&watchdog_timer, clocksource_watchdog, TIMER_PINNED);
watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
watchdog_running = 1;
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index b8b541caed48..a428d94084ee 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1677,10 +1677,21 @@ static void __queue_delayed_work(int cpu, struct workqueue_struct *wq,
dwork->cpu = cpu;
timer->expires = jiffies + delay;

- if (unlikely(cpu != WORK_CPU_UNBOUND))
+ if (unlikely(cpu != WORK_CPU_UNBOUND)) {
+ /*
+ * TODO: Setting the flag is a workaround for now; needs to
+ * be cleaned up with new work initializers and defines
+ */
+ timer->flags |= TIMER_PINNED;
add_timer_on(timer, cpu);
- else
+ } else {
+ /*
+ * TODO: Resetting the flag is a workaround for now; needs
+ * to be cleaned up with new work initializers and defines
+ */
+ timer->flags &= ~TIMER_PINNED;
add_timer(timer);
+ }
}

/**
--
2.30.2