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Frederic Weisbecker b416514054 entry/rcu: Check TIF_RESCHED _after_ delayed RCU wake-up 
RCU sometimes needs to perform a delayed wake up for specific kthreads
handling offloaded callbacks (RCU_NOCB).  These wakeups are performed
by timers and upon entry to idle (also to guest and to user on nohz_full).

However the delayed wake-up on kernel exit is actually performed after
the thread flags are fetched towards the fast path check for work to
do on exit to user. As a result, and if there is no other pending work
to do upon that kernel exit, the current task will resume to userspace
with TIF_RESCHED set and the pending wake up ignored.

Fix this with fetching the thread flags _after_ the delayed RCU-nocb
kthread wake-up.

Fixes: 47b8ff194c ("entry: Explicitly flush pending rcuog wakeup before last rescheduling point")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230315194349.10798-3-joel@joelfernandes.org
2023-03-21 15:13:15 +01:00
..
common.c entry/rcu: Check TIF_RESCHED _after_ delayed RCU wake-up 2023-03-21 15:13:15 +01:00
common.h kernel: Implement selective syscall userspace redirection 2020-12-02 15:07:56 +01:00
kvm.c entry/kvm: Exit to user mode when TIF_NOTIFY_SIGNAL is set 2022-06-07 11:19:00 -04:00
Makefile kernel: Implement selective syscall userspace redirection 2020-12-02 15:07:56 +01:00
syscall_user_dispatch.c signal: Replace force_fatal_sig with force_exit_sig when in doubt 2021-11-19 09:15:58 -06:00