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authorChuansheng Liu <chuansheng.liu@intel.com>2014-02-24 11:29:50 +0800
committerThomas Gleixner <tglx@linutronix.de>2014-02-27 10:54:16 +0100
commitc685689fd24d310343ac33942e9a54a974ae9c43 (patch)
tree998f7faccc33aecb3bdf3cee4e9f8d1f5728dd26 /kernel
parent6dba6ecba7d937e9b04b46f6cdff25e574f64857 (diff)
downloadlinux-c685689fd24d310343ac33942e9a54a974ae9c43.tar.bz2
genirq: Remove racy waitqueue_active check
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 Cc: stable@vger.kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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 481a13c43b17..d3bf660cb57f 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -802,8 +802,7 @@ 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);
}