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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