Author: tychon
Date: Tue Oct 13 18:28:48 2020
New Revision: 366678
URL: https://svnweb.freebsd.org/changeset/base/366678
Log:
eliminate possible race in parallel TLB shootdown IPI
On the target side TLB shootdown IPI handler, prevent the compiler
from performing a forward store optimization which may mask a
subsequent update to the scoreboard by the initiator.
Reported by: Max Laier, Anton Rang
Discussed with: kib
Sponsored by: Dell EMC Isilon
Modified:
head/sys/amd64/amd64/mp_machdep.c
Modified: head/sys/amd64/amd64/mp_machdep.c
==============================================================================
--- head/sys/amd64/amd64/mp_machdep.c Tue Oct 13 18:04:19 2020
(r366677)
+++ head/sys/amd64/amd64/mp_machdep.c Tue Oct 13 18:28:48 2020
(r366678)
@@ -1094,7 +1094,7 @@ invlop_handler(void)
for (;;) {
for (initiator_cpu_id = 0; initiator_cpu_id <= mp_maxid;
initiator_cpu_id++) {
- if (scoreboard[initiator_cpu_id] == 0)
+ if (atomic_load_int(&scoreboard[initiator_cpu_id]) == 0)
break;
}
if (initiator_cpu_id > mp_maxid)
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