hrtimer: Prevent all reprogramming if hang detected

[cascardo/linux.git] / kernel / hrtimer.c

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index d55092c..e3724fd 100644 (file)
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -569,6 +569,23 @@ hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
 
        cpu_base->expires_next.tv64 = expires_next.tv64;
 
+       /*
+        * If a hang was detected in the last timer interrupt then we
+        * leave the hang delay active in the hardware. We want the
+        * system to make progress. That also prevents the following
+        * scenario:
+        * T1 expires 50ms from now
+        * T2 expires 5s from now
+        *
+        * T1 is removed, so this code is called and would reprogram
+        * the hardware to 5s from now. Any hrtimer_start after that
+        * will not reprogram the hardware due to hang_detected being
+        * set. So we'd effectivly block all timers until the T2 event
+        * fires.
+        */
+       if (cpu_base->hang_detected)
+               return;
+
        if (cpu_base->expires_next.tv64 != KTIME_MAX)
                tick_program_event(cpu_base->expires_next, 1);
 }