Author: markj
Date: Tue Jul 5 17:59:04 2016
New Revision: 302346
URL: https://svnweb.freebsd.org/changeset/base/302346
Log:
Ensure that spinlock sections are balanced even after a panic.
vpanic() uses spinlock_enter() to disable interrupts before dumping core.
However, when the scheduler is stopped and INVARIANTS is not configured,
thread_lock() does not acquire a spinlock section, while thread_unlock()
releases one. This can result in interrupts staying enabled while the
kernel dumps core, complicating post-mortem analysis of the crash.
Approved by: re (gjb)
MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division
Modified:
head/sys/kern/kern_mutex.c
Modified: head/sys/kern/kern_mutex.c
==============================================================================
--- head/sys/kern/kern_mutex.c Tue Jul 5 16:37:01 2016 (r302345)
+++ head/sys/kern/kern_mutex.c Tue Jul 5 17:59:04 2016 (r302346)
@@ -657,8 +657,15 @@ thread_lock_flags_(struct thread *td, in
i = 0;
tid = (uintptr_t)curthread;
- if (SCHEDULER_STOPPED())
+ if (SCHEDULER_STOPPED()) {
+ /*
+ * Ensure that spinlock sections are balanced even when the
+ * scheduler is stopped, since we may otherwise inadvertently
+ * re-enable interrupts while dumping core.
+ */
+ spinlock_enter();
return;
+ }
#ifdef KDTRACE_HOOKS
spin_time -= lockstat_nsecs(&td->td_lock->lock_object);
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