timerfd: Prepare for PREEMPT_RT

Use the hrtimer_cancel_wait_running() synchronization mechanism to prevent priority inversion and live locks on PREEMPT_RT. [ tglx: Split out of combo patch ] Signed-off-by: Anna-Maria Gleixner <[email protected]> Signed-off-by: Sebastian Andrzej Siewior <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Acked-by: Peter Zijlstra (Intel) <[email protected]> Link: https://lkml.kernel.org/r/[email protected]
tadfisher · Aug 1, 2019 · a125ecc · a125ecc
1 parent 51ae330
commit a125ecc
Showing 1 changed file with 5 additions and 1 deletion.
diff --git a/fs/timerfd.c b/fs/timerfd.c
@@ -471,7 +471,11 @@ static int do_timerfd_settime(int ufd, int flags,
 				break;
 		}
 		spin_unlock_irq(&ctx->wqh.lock);
-		cpu_relax();
+
+		if (isalarm(ctx))
+			hrtimer_cancel_wait_running(&ctx->t.alarm.timer);
+		else
+			hrtimer_cancel_wait_running(&ctx->t.tmr);
 	}
 
 	/*