diff options
| author | Mark Johnston <markj@FreeBSD.org> | 2022-09-23 23:41:30 +0000 |
|---|---|---|
| committer | Mark Johnston <markj@FreeBSD.org> | 2022-09-24 00:09:06 +0000 |
| commit | c2d27b0ec7000d28b4f31148005ccfe371f47db3 (patch) | |
| tree | c6504f3786bef3f3036a8a8e2012a5b627d7d61e | |
| parent | 7652321b7909002877cabcaee56dc996814070e8 (diff) | |
| download | src-c2d27b0ec7000d28b4f31148005ccfe371f47db3.tar.gz src-c2d27b0ec7000d28b4f31148005ccfe371f47db3.zip | |
sched_4bsd: Fix a racy thread state modification
When a thread switching off-CPU is migrating to a remote CPU,
sched_switch() may trigger a rescheduling of the thread currently
running on that CPU. When doing so, it must ensure that that thread is
locked before modifying thread state. If the thread's lock is not the
scheduler lock, then the thread is in the process of switching off-CPU
and no extra effort is needed, and the initiator does not hold the
thread's lock and thus should not modify any thread state.
Reported and tested by: Steve Kargl
MFC after: 1 week
| -rw-r--r-- | sys/kern/sched_4bsd.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/sys/kern/sched_4bsd.c b/sys/kern/sched_4bsd.c index 9d48aa746f6d..8bd697a67e7e 100644 --- a/sys/kern/sched_4bsd.c +++ b/sys/kern/sched_4bsd.c @@ -1282,9 +1282,10 @@ kick_other_cpu(int pri, int cpuid) } #endif /* defined(IPI_PREEMPTION) && defined(PREEMPTION) */ - ast_sched_locked(pcpu->pc_curthread, TDA_SCHED); - ipi_cpu(cpuid, IPI_AST); - return; + if (pcpu->pc_curthread->td_lock == &sched_lock) { + ast_sched_locked(pcpu->pc_curthread, TDA_SCHED); + ipi_cpu(cpuid, IPI_AST); + } } #endif /* SMP */ |