diff options
| author | Paul E. McKenney <paulmck@kernel.org> | 2020-03-12 16:55:07 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-04-21 09:08:14 +0200 |
| commit | fe092f4ded424c212d2611d15441a8e8609706b7 (patch) | |
| tree | dc0712d57495465d37f257fcdfc2fee11f30faf0 /kernel | |
| parent | 634781fc6f75bd185907607bd22d275ed49d82f8 (diff) | |
rcu: Don't acquire lock in NMI handler in rcu_nmi_enter_common()
commit bf37da98c51825c90432d340e135cced37a7460d upstream.
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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
| -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 c0a9865b1f6a..fbb484a2e3e8 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -816,7 +816,7 @@ 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) && !rdp->rcu_forced_tick) { raw_spin_lock_rcu_node(rdp->mynode); |