Messages in this thread Patch in this message | | | Date | Tue, 04 Mar 2014 19:33:34 -0500 | From | Steven Rostedt <> | Subject | [PATCH RT 1/6] rcutree/rcu_bh_qs: disable irq while calling rcu_preempt_qs() |
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3.2.55-rt79-rc1 stable review patch. If anyone has any objections, please let me know.
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From: Tiejun Chen <tiejun.chen@windriver.com>
Any callers to the function rcu_preempt_qs() must disable irqs in order to protect the assignment to ->rcu_read_unlock_special. In RT case, rcu_bh_qs() as the wrapper of rcu_preempt_qs() is called in some scenarios where irq is enabled, like this path,
do_single_softirq() | + local_irq_enable(); + handle_softirq() | | | + rcu_bh_qs() | | | + rcu_preempt_qs() | + local_irq_disable()
So here we'd better disable irq directly inside of rcu_bh_qs() to fix this, otherwise the kernel may be freezable sometimes as observed. And especially this way is also kind and safe for the potential rcu_bh_qs() usage elsewhere in the future.
Cc: stable-rt@vger.kernel.org Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com> Signed-off-by: Bin Jiang <bin.jiang@windriver.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> --- kernel/rcutree.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 82c2224..6c2ec2d 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -175,7 +175,12 @@ static void rcu_preempt_qs(int cpu); void rcu_bh_qs(int cpu) { + unsigned long flags; + + /* Callers to this function, rcu_preempt_qs(), must disable irqs. */ + local_irq_save(flags); rcu_preempt_qs(cpu); + local_irq_restore(flags); } #else void rcu_bh_qs(int cpu) -- 1.8.5.3
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