Date: Fri, 8 Jun 2018 18:32:27 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r334851 - head/sys/arm64/arm64 Message-ID: <201806081832.w58IWRth024945@repo.freebsd.org>
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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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