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[PATCH RT 5/8] timer-fd: Prevent live lock

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From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

If hrtimer_try_to_cancel() requires a retry, then depending on the
priority setting te retry loop might prevent timer callback completion
on RT. Prevent that by waiting for completion on RT, no change for a
non RT kernel.

Reported-by: Sankara Muthukrishnan <sankara.m@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: stable-rt@xxxxxxxxxxxxxxx
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 fs/timerfd.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/timerfd.c b/fs/timerfd.c
index dffeb37..57f0e4e 100644
--- a/fs/timerfd.c
+++ b/fs/timerfd.c
@@ -313,7 +313,7 @@ SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
 		if (hrtimer_try_to_cancel(&ctx->tmr) >= 0)
 			break;
 		spin_unlock_irq(&ctx->wqh.lock);
-		cpu_relax();
+		hrtimer_wait_for_timer(&ctx->tmr);
 	}
 
 	/*
-- 
1.7.8.3


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