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When updating/accessing the timehands, barriers are needed to ensure
that: - th_generation update is visible after the parameters update is visible; - the read of parameters is not reordered before initial read of th_generation. On UP kernels, compiler barriers are enough. For SMP machines, CPU barriers must be used too, as was confirmed by submitter by testing on the Freescale T4240 platform with 24 PowerPC processors. Submitted by: Sebastian Huber <sebastian.huber@embedded-brains.de> MFC after: 1 week
This commit is contained in:
Konstantin Belousov
parent
125954c873
commit
2c6946dca2
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=284178
@ -34,6 +34,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/timetc.h>
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#include <sys/timex.h>
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#include <sys/vdso.h>
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#include <machine/atomic.h>
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/*
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* A large step happens on boot. This constant detects such steps.
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@ -71,7 +72,7 @@ struct timehands {
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struct timeval th_microtime;
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struct timespec th_nanotime;
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/* Fields not to be copied in tc_windup start with th_generation. */
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volatile u_int th_generation;
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u_int th_generation;
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struct timehands *th_next;
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};
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@ -189,6 +190,33 @@ tc_delta(struct timehands *th)
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tc->tc_counter_mask);
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}
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static u_int
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tc_getgen(struct timehands *th)
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{
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#ifdef SMP
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return (atomic_load_acq_int(&th->th_generation));
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#else
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u_int gen;
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gen = th->th_generation;
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__compiler_membar();
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return (gen);
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#endif
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}
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static void
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tc_setgen(struct timehands *th, u_int newgen)
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{
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#ifdef SMP
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atomic_store_rel_int(&th->th_generation, newgen);
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#else
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__compiler_membar();
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th->th_generation = newgen;
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#endif
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}
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/*
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* Functions for reading the time. We have to loop until we are sure that
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* the timehands that we operated on was not updated under our feet. See
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@ -204,10 +232,10 @@ fbclock_binuptime(struct bintime *bt)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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*bt = th->th_offset;
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bintime_addx(bt, th->th_scale * tc_delta(th));
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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}
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void
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@ -262,9 +290,9 @@ fbclock_getbinuptime(struct bintime *bt)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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*bt = th->th_offset;
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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}
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void
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@ -275,9 +303,9 @@ fbclock_getnanouptime(struct timespec *tsp)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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bintime2timespec(&th->th_offset, tsp);
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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}
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void
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@ -288,9 +316,9 @@ fbclock_getmicrouptime(struct timeval *tvp)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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bintime2timeval(&th->th_offset, tvp);
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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}
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void
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@ -301,9 +329,9 @@ fbclock_getbintime(struct bintime *bt)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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*bt = th->th_offset;
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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bintime_add(bt, &boottimebin);
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}
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@ -315,9 +343,9 @@ fbclock_getnanotime(struct timespec *tsp)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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*tsp = th->th_nanotime;
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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}
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void
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@ -328,9 +356,9 @@ fbclock_getmicrotime(struct timeval *tvp)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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*tvp = th->th_microtime;
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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}
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#else /* !FFCLOCK */
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void
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@ -341,10 +369,10 @@ binuptime(struct bintime *bt)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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*bt = th->th_offset;
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bintime_addx(bt, th->th_scale * tc_delta(th));
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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}
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void
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@ -399,9 +427,9 @@ getbinuptime(struct bintime *bt)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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*bt = th->th_offset;
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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}
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void
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@ -412,9 +440,9 @@ getnanouptime(struct timespec *tsp)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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bintime2timespec(&th->th_offset, tsp);
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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}
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void
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@ -425,9 +453,9 @@ getmicrouptime(struct timeval *tvp)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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bintime2timeval(&th->th_offset, tvp);
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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}
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void
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@ -438,9 +466,9 @@ getbintime(struct bintime *bt)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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*bt = th->th_offset;
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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bintime_add(bt, &boottimebin);
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}
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@ -452,9 +480,9 @@ getnanotime(struct timespec *tsp)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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*tsp = th->th_nanotime;
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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}
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void
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@ -465,9 +493,9 @@ getmicrotime(struct timeval *tvp)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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*tvp = th->th_microtime;
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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}
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#endif /* FFCLOCK */
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@ -880,11 +908,11 @@ ffclock_read_counter(ffcounter *ffcount)
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*/
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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ffth = fftimehands;
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delta = tc_delta(th);
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*ffcount = ffth->tick_ffcount;
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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*ffcount += delta;
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}
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@ -988,9 +1016,9 @@ dtrace_getnanotime(struct timespec *tsp)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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*tsp = th->th_nanotime;
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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}
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/*
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@ -1028,7 +1056,7 @@ sysclock_getsnapshot(struct sysclock_snap *clock_snap, int fast)
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do {
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th = timehands;
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gen = th->th_generation;
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gen = tc_getgen(th);
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fbi->th_scale = th->th_scale;
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fbi->tick_time = th->th_offset;
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#ifdef FFCLOCK
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@ -1042,7 +1070,7 @@ sysclock_getsnapshot(struct sysclock_snap *clock_snap, int fast)
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#endif
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if (!fast)
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delta = tc_delta(th);
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} while (gen == 0 || gen != th->th_generation);
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} while (gen == 0 || gen != tc_getgen(th));
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clock_snap->delta = delta;
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clock_snap->sysclock_active = sysclock_active;
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@ -1260,7 +1288,7 @@ tc_windup(void)
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tho = timehands;
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th = tho->th_next;
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ogen = th->th_generation;
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th->th_generation = 0;
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tc_setgen(th, 0);
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bcopy(tho, th, offsetof(struct timehands, th_generation));
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/*
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@ -1377,7 +1405,7 @@ tc_windup(void)
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*/
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if (++ogen == 0)
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ogen = 1;
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th->th_generation = ogen;
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tc_setgen(th, ogen);
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/* Go live with the new struct timehands. */
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#ifdef FFCLOCK
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@ -1651,13 +1679,13 @@ pps_capture(struct pps_state *pps)
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KASSERT(pps != NULL, ("NULL pps pointer in pps_capture"));
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th = timehands;
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pps->capgen = th->th_generation;
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pps->capgen = tc_getgen(th);
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pps->capth = th;
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#ifdef FFCLOCK
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pps->capffth = fftimehands;
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#endif
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pps->capcount = th->th_counter->tc_get_timecount(th->th_counter);
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if (pps->capgen != th->th_generation)
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if (pps->capgen != tc_getgen(th))
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pps->capgen = 0;
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}
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@ -1677,7 +1705,7 @@ pps_event(struct pps_state *pps, int event)
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KASSERT(pps != NULL, ("NULL pps pointer in pps_event"));
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/* If the timecounter was wound up underneath us, bail out. */
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if (pps->capgen == 0 || pps->capgen != pps->capth->th_generation)
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if (pps->capgen == 0 || pps->capgen != tc_getgen(pps->capth))
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return;
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/* Things would be easier with arrays. */
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@ -1727,7 +1755,7 @@ pps_event(struct pps_state *pps, int event)
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bintime2timespec(&bt, &ts);
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/* If the timecounter was wound up underneath us, bail out. */
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if (pps->capgen != pps->capth->th_generation)
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if (pps->capgen != tc_getgen(pps->capth))
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return;
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*pcount = pps->capcount;
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