Date: Mon, 18 Dec 2017 17:26:25 +0000 (UTC) From: Mark Johnston <markj@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r326935 - in head/sys/cddl/dev/dtrace: amd64 i386 Message-ID: <201712181726.vBIHQPor013173@repo.freebsd.org>
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Author: markj Date: Mon Dec 18 17:26:24 2017 New Revision: 326935 URL: https://svnweb.freebsd.org/changeset/base/326935 Log: Avoid CPU migration in dtrace_gethrtime() on x86. dtrace_gethrtime() may be called outside of probe context, and in particular, from the DTRACEIOC_BUFSNAP handler. Disable interrupts rather than using sched_pin() to help ensure that we don't call any external functions when in probe context. PR: 218452 MFC after: 1 week Modified: head/sys/cddl/dev/dtrace/amd64/dtrace_subr.c head/sys/cddl/dev/dtrace/i386/dtrace_subr.c Modified: head/sys/cddl/dev/dtrace/amd64/dtrace_subr.c ============================================================================== --- head/sys/cddl/dev/dtrace/amd64/dtrace_subr.c Mon Dec 18 17:17:07 2017 (r326934) +++ head/sys/cddl/dev/dtrace/amd64/dtrace_subr.c Mon Dec 18 17:26:24 2017 (r326935) @@ -353,11 +353,11 @@ SYSINIT(dtrace_gethrtime_init, SI_SUB_SMP, SI_ORDER_AN * Returns nanoseconds since boot. */ uint64_t -dtrace_gethrtime() +dtrace_gethrtime(void) { uint64_t tsc; - uint32_t lo; - uint32_t hi; + uint32_t lo, hi; + register_t rflags; /* * We split TSC value into lower and higher 32-bit halves and separately @@ -365,7 +365,10 @@ dtrace_gethrtime() * (see nsec_scale calculations) taking into account 32-bit shift of * the higher half and finally add. */ + rflags = intr_disable(); tsc = rdtsc() - tsc_skew[curcpu]; + intr_restore(rflags); + lo = tsc; hi = tsc >> 32; return (((lo * nsec_scale) >> SCALE_SHIFT) + Modified: head/sys/cddl/dev/dtrace/i386/dtrace_subr.c ============================================================================== --- head/sys/cddl/dev/dtrace/i386/dtrace_subr.c Mon Dec 18 17:17:07 2017 (r326934) +++ head/sys/cddl/dev/dtrace/i386/dtrace_subr.c Mon Dec 18 17:26:24 2017 (r326935) @@ -355,11 +355,11 @@ SYSINIT(dtrace_gethrtime_init, SI_SUB_SMP, SI_ORDER_AN * Returns nanoseconds since boot. */ uint64_t -dtrace_gethrtime() +dtrace_gethrtime(void) { uint64_t tsc; - uint32_t lo; - uint32_t hi; + uint32_t lo, hi; + register_t eflags; /* * We split TSC value into lower and higher 32-bit halves and separately @@ -367,7 +367,10 @@ dtrace_gethrtime() * (see nsec_scale calculations) taking into account 32-bit shift of * the higher half and finally add. */ + eflags = intr_disable(); tsc = rdtsc() - tsc_skew[curcpu]; + intr_restore(eflags); + lo = tsc; hi = tsc >> 32; return (((lo * nsec_scale) >> SCALE_SHIFT) +
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