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entry: Explicitly flush pending rcuog wakeup before last rescheduling point

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Following the idle loop model, cleanly check for pending rcuog wakeup
before the last rescheduling point on resuming to user mode. This
way we can avoid to do it from rcu_user_enter() with the last resort
self-IPI hack that enforces rescheduling.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210131230548.32970-5-frederic@kernel.org
This commit is contained in:
Frederic Weisbecker
2021-02-01 00:05:47 +01:00
committed by Ingo Molnar
parent f8bb5cae96
commit 47b8ff194c
2 changed files with 14 additions and 5 deletions
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7
kernel/entry/common.c
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@@ -184,6 +184,10 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
* enabled above.
*/
local_irq_disable_exit_to_user();
/* Check if any of the above work has queued a deferred wakeup */
rcu_nocb_flush_deferred_wakeup();
ti_work = READ_ONCE(current_thread_info()->flags);
}
@@ -197,6 +201,9 @@ static void exit_to_user_mode_prepare(struct pt_regs *regs)
lockdep_assert_irqs_disabled();
/* Flush pending rcuog wakeup before the last need_resched() check */
rcu_nocb_flush_deferred_wakeup();
if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
ti_work = exit_to_user_mode_loop(regs, ti_work);