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authorPeter Zijlstra <peterz@infradead.org>2021-10-18 16:41:05 +0200
committerPeter Zijlstra <peterz@infradead.org>2021-10-22 15:32:46 +0200
commit96611c26dc351c33f73b48756a9feacc109e5bab (patch)
treed1feeaf18f00f6777dceb73620de7938c94f2a13 /kernel/smp.c
parent09089db79859cbccccd8df95b034f36f7027efa6 (diff)
sched: Improve wake_up_all_idle_cpus() take #2
As reported by syzbot and experienced by Pavel, using cpus_read_lock() in wake_up_all_idle_cpus() generates lock inversion (against mmap_sem and possibly others). Instead, shrink the preempt disable region by iterating all CPUs and checking the online status for each individual CPU while having preemption disabled. Fixes: 8850cb663b5c ("sched: Simplify wake_up_*idle*()") Reported-by: syzbot+d5b23b18d2f4feae8a67@syzkaller.appspotmail.com Reported-by: Pavel Machek <pavel@ucw.cz> Reported-by: Qian Cai <quic_qiancai@quicinc.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Qian Cai <quic_qiancai@quicinc.com>
Diffstat (limited to 'kernel/smp.c')
-rw-r--r--kernel/smp.c12
1 files changed, 5 insertions, 7 deletions
diff --git a/kernel/smp.c b/kernel/smp.c
index ad0b68a3a3d3..01a7c1706a58 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -1170,14 +1170,12 @@ void wake_up_all_idle_cpus(void)
{
int cpu;
- cpus_read_lock();
- for_each_online_cpu(cpu) {
- if (cpu == raw_smp_processor_id())
- continue;
-
- wake_up_if_idle(cpu);
+ for_each_possible_cpu(cpu) {
+ preempt_disable();
+ if (cpu != smp_processor_id() && cpu_online(cpu))
+ wake_up_if_idle(cpu);
+ preempt_enable();
}
- cpus_read_unlock();
}
EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus);