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| author | Paul E. McKenney <paulmck@kernel.org> | 2020-03-12 16:55:07 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-04-05 14:22:15 -0700 |
| commit | bf37da98c51825c90432d340e135cced37a7460d (patch) | |
| tree | bce8b75a3caa6a7f7feeadb20187c7c5f2851539 /kernel/rcu | |
| parent | aa93ec620be378cce1454286122915533ff8fa48 (diff) | |
| download | linux-bf37da98c51825c90432d340e135cced37a7460d.tar.bz2 | |
rcu: Don't acquire lock in NMI handler in rcu_nmi_enter_common()
The rcu_nmi_enter_common() function can be invoked both in interrupt
and NMI handlers. If it is invoked from process context (as opposed
to userspace or idle context) on a nohz_full CPU, it might acquire the
CPU's leaf rcu_node structure's ->lock. Because this lock is held only
with interrupts disabled, this is safe from an interrupt handler, but
doing so from an NMI handler can result in self-deadlock.
This commit therefore adds "irq" to the "if" condition so as to only
acquire the ->lock from irq handlers or process context, never from
an NMI handler.
Fixes: 5b14557b073c ("rcu: Avoid tick_dep_set_cpu() misordering")
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: <stable@vger.kernel.org> # 5.5.x
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 550193a9ce76..2c17859233db 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -825,7 +825,7 @@ static __always_inline void rcu_nmi_enter_common(bool irq) rcu_cleanup_after_idle(); incby = 1; - } else if (tick_nohz_full_cpu(rdp->cpu) && + } else if (irq && tick_nohz_full_cpu(rdp->cpu) && rdp->dynticks_nmi_nesting == DYNTICK_IRQ_NONIDLE && READ_ONCE(rdp->rcu_urgent_qs) && !READ_ONCE(rdp->rcu_forced_tick)) { |