diff options
| author | Dexuan Cui <[email protected]> | 2018-05-15 19:52:50 +0000 |
|---|---|---|
| committer | Thomas Gleixner <[email protected]> | 2018-05-15 22:45:54 +0200 |
| commit | 5596fe34495cf0f645f417eb928ef224df3e3cb4 (patch) | |
| tree | 4f4586ef828c6f79c94a048f5d891c386d17ca37 | |
| parent | 67b8d5c7081221efa252e111cd52532ec6d4266f (diff) | |
tick/broadcast: Use for_each_cpu() specially on UP kernels
for_each_cpu() unintuitively reports CPU0 as set independent of the actual
cpumask content on UP kernels. This causes an unexpected PIT interrupt
storm on a UP kernel running in an SMP virtual machine on Hyper-V, and as
a result, the virtual machine can suffer from a strange random delay of 1~20
minutes during boot-up, and sometimes it can hang forever.
Protect if by checking whether the cpumask is empty before entering the
for_each_cpu() loop.
[ tglx: Use !IS_ENABLED(CONFIG_SMP) instead of #ifdeffery ]
Signed-off-by: Dexuan Cui <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Josh Poulson <[email protected]>
Cc: "Michael Kelley (EOSG)" <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: [email protected]
Cc: Rakib Mullick <[email protected]>
Cc: Jork Loeser <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: KY Srinivasan <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Link: https://lkml.kernel.org/r/KL1P15301MB000678289FE55BA365B3279ABF990@KL1P15301MB0006.APCP153.PROD.OUTLOOK.COM
Link: https://lkml.kernel.org/r/KL1P15301MB0006FA63BC22BEB64902EAA0BF930@KL1P15301MB0006.APCP153.PROD.OUTLOOK.COM
| -rw-r--r-- | kernel/time/tick-broadcast.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index b398c2ea69b2..aa2094d5dd27 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -612,6 +612,14 @@ static void tick_handle_oneshot_broadcast(struct clock_event_device *dev) now = ktime_get(); /* Find all expired events */ for_each_cpu(cpu, tick_broadcast_oneshot_mask) { + /* + * Required for !SMP because for_each_cpu() reports + * unconditionally CPU0 as set on UP kernels. + */ + if (!IS_ENABLED(CONFIG_SMP) && + cpumask_empty(tick_broadcast_oneshot_mask)) + break; + td = &per_cpu(tick_cpu_device, cpu); if (td->evtdev->next_event <= now) { cpumask_set_cpu(cpu, tmpmask); |