Author: kib
Date: Fri Jun 8 18:32:26 2018
New Revision: 334851
URL: https://svnweb.freebsd.org/changeset/base/334851
Log:
Restore release semantic for the old thread unlock on arm64.
With the introduction of pmap_switch(), the DSB instruction on the
address map switch is not necessary executed, which is fixed by
changing the unlock store to release. Also remove comment which
documented pre-pmap_switch() code.
Reviewed by: andrew
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Modified:
head/sys/arm64/arm64/swtch.S
Modified: head/sys/arm64/arm64/swtch.S
==============================================================================
--- head/sys/arm64/arm64/swtch.S Fri Jun 8 18:24:46 2018
(r334850)
+++ head/sys/arm64/arm64/swtch.S Fri Jun 8 18:32:26 2018
(r334851)
@@ -165,10 +165,9 @@ ENTRY(cpu_switch)
mov x0, x19
/*
- * Release the old thread. This doesn't need to be a store-release
- * as the above dsb instruction will provide release semantics.
+ * Release the old thread.
*/
- str x2, [x0, #TD_LOCK]
+ stlr x2, [x0, #TD_LOCK]
#if defined(SCHED_ULE) && defined(SMP)
/* Spin if TD_LOCK points to a blocked_lock */
ldr x2, =_C_LABEL(blocked_lock)
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