Author: kib
Date: Tue Oct 18 10:33:28 2016
New Revision: 307555
URL: https://svnweb.freebsd.org/changeset/base/307555
Log:
MFC r307064:
When downgrading exclusively busied page to shared-busy state, wakeup
waiters.
Modified:
stable/10/sys/vm/vm_page.c
Directory Properties:
stable/10/ (props changed)
Modified: stable/10/sys/vm/vm_page.c
==============================================================================
--- stable/10/sys/vm/vm_page.c Tue Oct 18 10:20:58 2016 (r307554)
+++ stable/10/sys/vm/vm_page.c Tue Oct 18 10:33:28 2016 (r307555)
@@ -515,15 +515,26 @@ void
vm_page_busy_downgrade(vm_page_t m)
{
u_int x;
+ bool locked;
vm_page_assert_xbusied(m);
+ locked = mtx_owned(vm_page_lockptr(m));
for (;;) {
x = m->busy_lock;
x &= VPB_BIT_WAITERS;
+ if (x != 0 && !locked)
+ vm_page_lock(m);
if (atomic_cmpset_rel_int(&m->busy_lock,
- VPB_SINGLE_EXCLUSIVER | x, VPB_SHARERS_WORD(1) | x))
+ VPB_SINGLE_EXCLUSIVER | x, VPB_SHARERS_WORD(1)))
break;
+ if (x != 0 && !locked)
+ vm_page_unlock(m);
+ }
+ if (x != 0) {
+ wakeup(m);
+ if (!locked)
+ vm_page_unlock(m);
}
}
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