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| author | Frederic Weisbecker <frederic@kernel.org> | 2023-03-15 22:43:43 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-03-30 13:49:13 +0300 |
| commit | d716ea059cd3d6abfbedda164a67b3659e19d2de (patch) | |
| tree | 6dc894b0638655f7f5916c069919c703713700b2 | |
| parent | ab33a8f7649b0324639a336e1081aaea51a4523e (diff) | |
| download | linux-d716ea059cd3d6abfbedda164a67b3659e19d2de.tar.xz | |
entry/rcu: Check TIF_RESCHED _after_ delayed RCU wake-up
[ Upstream commit b416514054810cf2d2cc348ae477cea619b64da7 ]
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: 47b8ff194c1f ("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
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | kernel/entry/common.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/entry/common.c b/kernel/entry/common.c index 1314894d2efa..be61332c66b5 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -192,13 +192,14 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs, static void exit_to_user_mode_prepare(struct pt_regs *regs) { - unsigned long ti_work = read_thread_flags(); + unsigned long ti_work; lockdep_assert_irqs_disabled(); /* Flush pending rcuog wakeup before the last need_resched() check */ tick_nohz_user_enter_prepare(); + ti_work = read_thread_flags(); if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK)) ti_work = exit_to_user_mode_loop(regs, ti_work); |