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SubjectRe: [PATCH] rcu: Fix missing TICK_DEP_MASK_RCU_EXP dependency check
On Tue, Dec 20, 2022 at 10:16:25PM +0800, Zqiang wrote:
> This commit add TICK_DEP_MASK_RCU_EXP dependency check in
> check_tick_dependency(), fix commit df1e849ae4559 ("rcu: Enable
> tick for nohz_full CPUs slow to provide expedited QS").
>
> Signed-off-by: Zqiang <qiang1.zhang@intel.com>

Again, good eyes, thank you!!!

I have queued this for further review and testing, given that it affects
pretty much only RCU. However, if someone else would rather take it:

Acked-by: Paul E. McKenney <paulmck@kernel.org>

Thanx, Paul

------------------------------------------------------------------------

commit f22caef6cda5ed19a55ec2e703f60f1fa85e52bc
Author: Zqiang <qiang1.zhang@intel.com>
Date: Tue Dec 20 22:16:25 2022 +0800

rcu: Fix missing TICK_DEP_MASK_RCU_EXP dependency check

This commit adds checks for the TICK_DEP_MASK_RCU_EXP bit, thus enabling
RCU expedited grace periods to actually force-enable scheduling-clock
interrupts on holdout CPUs.

Fixes: df1e849ae455 ("rcu: Enable tick for nohz_full CPUs slow to provide expedited QS")
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index 2e713a7d9aa3a..3e8619c72f774 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -371,7 +371,8 @@ TRACE_EVENT(itimer_expire,
tick_dep_name(PERF_EVENTS) \
tick_dep_name(SCHED) \
tick_dep_name(CLOCK_UNSTABLE) \
- tick_dep_name_end(RCU)
+ tick_dep_name(RCU) \
+ tick_dep_name_end(RCU_EXP)

#undef tick_dep_name
#undef tick_dep_mask_name
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index b0e3c9205946f..ba2ac1469d473 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -281,6 +281,11 @@ static bool check_tick_dependency(atomic_t *dep)
return true;
}

+ if (val & TICK_DEP_MASK_RCU_EXP) {
+ trace_tick_stop(0, TICK_DEP_MASK_RCU_EXP);
+ return true;
+ }
+
return false;
}

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