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Subject: timer-fd: Prevent live lock
From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 25 Jan 2012 11:08:40 +0100
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.9/older/patches-4.9.20-rt16.tar.xz
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@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
fs/timerfd.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/fs/timerfd.c
+++ b/fs/timerfd.c
@@ -460,7 +460,10 @@ static int do_timerfd_settime(int ufd, i
break;
}
spin_unlock_irq(&ctx->wqh.lock);
- cpu_relax();
+ if (isalarm(ctx))
+ hrtimer_wait_for_timer(&ctx->t.alarm.timer);
+ else
+ hrtimer_wait_for_timer(&ctx->t.tmr);
}
/*
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