From 0e4097c3354e2f5a5ad8affd9dc7f7f7d00bb6b9 Mon Sep 17 00:00:00 2001
From: Wanpeng Li <wanpeng.li@hotmail.com>
Date: Sun, 9 Jul 2017 00:40:28 -0700
Subject: [PATCH] sched/cputime: Don't use smp_processor_id() in preemptible
context
Recent kernels trigger this warning:
BUG: using smp_processor_id() in preemptible [00000000] code: 99-trinity/181
caller is debug_smp_processor_id+0x17/0x19
CPU: 0 PID: 181 Comm: 99-trinity Not tainted 4.12.0-01059-g2a42eb9 #1
Call Trace:
dump_stack+0x82/0xb8
check_preemption_disabled()
debug_smp_processor_id()
vtime_delta()
task_cputime()
thread_group_cputime()
thread_group_cputime_adjusted()
wait_consider_task()
do_wait()
SYSC_wait4()
do_syscall_64()
entry_SYSCALL64_slow_path()
As Frederic pointed out:
| Although those sched_clock_cpu() things seem to only matter when the
| sched_clock() is unstable. And that stability is a condition for nohz_full
| to work anyway. So probably sched_clock() alone would be enough.
This patch fixes it by replacing sched_clock_cpu() with sched_clock() to
avoid calling smp_processor_id() in a preemptible context.
Reported-by: Xiaolong Ye <xiaolong.ye@intel.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1499586028-7402-1-git-send-email-wanpeng.li@hotmail.com
[ Prettified the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/cputime.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 6e3ea4ac1bdaf..14d2dbf97c531 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -683,7 +683,7 @@ static u64 vtime_delta(struct vtime *vtime)
{
unsigned long long clock;
- clock = sched_clock_cpu(smp_processor_id());
+ clock = sched_clock();
if (clock < vtime->starttime)
return 0;
@@ -814,7 +814,7 @@ void arch_vtime_task_switch(struct task_struct *prev)
write_seqcount_begin(&vtime->seqcount);
vtime->state = VTIME_SYS;
- vtime->starttime = sched_clock_cpu(smp_processor_id());
+ vtime->starttime = sched_clock();
write_seqcount_end(&vtime->seqcount);
}
@@ -826,7 +826,7 @@ void vtime_init_idle(struct task_struct *t, int cpu)
local_irq_save(flags);
write_seqcount_begin(&vtime->seqcount);
vtime->state = VTIME_SYS;
- vtime->starttime = sched_clock_cpu(cpu);
+ vtime->starttime = sched_clock();
write_seqcount_end(&vtime->seqcount);
local_irq_restore(flags);
}
--
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