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authorChuansheng Liu <chuansheng.liu@intel.com>2014-02-24 11:29:50 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-03-23 21:37:05 -0700
commitb46741f24d1c0d0d8dcfb3c63439338d2dc0337e (patch)
treee5c655ff39f3806adcd5601e44dcc67a49e74e04 /kernel
parentbb7d79fc8250eaa01ac6f82f9001ffcec0e7ca36 (diff)
genirq: Remove racy waitqueue_active check
commit c685689fd24d310343ac33942e9a54a974ae9c43 upstream. We hit one rare case below: T1 calling disable_irq(), but hanging at synchronize_irq() always; The corresponding irq thread is in sleeping state; And all CPUs are in idle state; After analysis, we found there is one possible scenerio which causes T1 is waiting there forever: CPU0 CPU1 synchronize_irq() wait_event() spin_lock() atomic_dec_and_test(&threads_active) insert the __wait into queue spin_unlock() if(waitqueue_active) atomic_read(&threads_active) wake_up() Here after inserted the __wait into queue on CPU0, and before test if queue is empty on CPU1, there is no barrier, it maybe cause it is not visible for CPU1 immediately, although CPU0 has updated the queue list. It is similar for CPU0 atomic_read() threads_active also. So we'd need one smp_mb() before waitqueue_active.that, but removing the waitqueue_active() check solves it as wel l and it makes things simple and clear. Signed-off-by: Chuansheng Liu <chuansheng.liu@intel.com> Cc: Xiaoming Wang <xiaoming.wang@intel.com> Link: http://lkml.kernel.org/r/1393212590-32543-1-git-send-email-chuansheng.liu@intel.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/irq/manage.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 86a500d7ea59..3d1bbbcc2923 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -777,8 +777,7 @@ static irqreturn_t irq_thread_fn(struct irq_desc *desc,
static void wake_threads_waitq(struct irq_desc *desc)
{
- if (atomic_dec_and_test(&desc->threads_active) &&
- waitqueue_active(&desc->wait_for_threads))
+ if (atomic_dec_and_test(&desc->threads_active))
wake_up(&desc->wait_for_threads);
}