Author: jah
Date: Sat Jan 14 19:35:36 2017
New Revision: 312191
URL: https://svnweb.freebsd.org/changeset/base/312191
Log:
Add comment explaining relative order of sched_unpin() and mtx_unlock().
Suggested by: alc
MFC after: 1 week
Modified:
head/sys/i386/i386/pmap.c
Modified: head/sys/i386/i386/pmap.c
==============================================================================
--- head/sys/i386/i386/pmap.c Sat Jan 14 18:04:12 2017 (r312190)
+++ head/sys/i386/i386/pmap.c Sat Jan 14 19:35:36 2017 (r312191)
@@ -4216,6 +4216,12 @@ pmap_zero_page(vm_page_t m)
invlcaddr(pc->pc_cmap_addr2);
pagezero(pc->pc_cmap_addr2);
*cmap_pte2 = 0;
+
+ /*
+ * Unpin the thread before releasing the lock. Otherwise the thread
+ * could be rescheduled while still bound to the current CPU, only
+ * to unpin itself immediately upon resuming execution.
+ */
sched_unpin();
mtx_unlock(&pc->pc_cmap_lock);
}
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