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Subject[PATCH] sched: Wake up all non-exclusive waiters in __wake_up_common()
Date
__wake_up_common() should wake up all non-exclusive waiters and
exclusive waiters as many as nr_exclusive, but currently it does not.

Consider a wait queue like the following for example:

A(exclusive) -> B(non-exclusive) -> C(non-exclusive)

Current code will wake up only A when nr_exclusive = 1, but has to wake
up A, B and C. Make it do as we expect.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
---
kernel/sched/wait.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 9453efe..0ea1083 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -67,12 +67,23 @@ static void __wake_up_common(wait_queue_head_t *q, unsigned int mode,
{
wait_queue_t *curr, *next;

+ /*
+ * We use nr_exclusive = 0 to wake up all no matter whether
+ * WQ_FLAG_EXCLUSIVE is set. However, we have to distinguish
+ * between the case and having finished all exclusive wake-up.
+ * So make nr_exclusive non-zero in advance in the former case.
+ */
+ nr_exclusive = nr_exclusive ?: -1;
+
list_for_each_entry_safe(curr, next, &q->task_list, task_list) {
unsigned flags = curr->flags;

+ if ((flags & WQ_FLAG_EXCLUSIVE) && !nr_exclusive)
+ continue;
+
if (curr->func(curr, mode, wake_flags, key) &&
- (flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive)
- break;
+ (flags & WQ_FLAG_EXCLUSIVE))
+ nr_exclusive--;
}
}

--
1.9.1
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