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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 21:38:15 -0700
commit56f1c4124bd0c769591071916abc5358b8811c1a (patch)
tree388d4eb722cdeb1ce8c076e13da61129bb7dfcef /kernel
parent3ec34db27ae6cc05ebb61732cbdeecce38c486c1 (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 dc4db3228dcd..9bd5c8a6c8ee 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);
}