diff options
| -rw-r--r-- | kernel/timer.c | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/kernel/timer.c b/kernel/timer.c index 1433d87f46b..13e2b513be0 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -1429,7 +1429,7 @@ static inline u64 time_interpolator_get_cycles(unsigned int src) } } -static inline u64 time_interpolator_get_counter(void) +static inline u64 time_interpolator_get_counter(int writelock) { unsigned int src = time_interpolator->source; @@ -1443,6 +1443,15 @@ static inline u64 time_interpolator_get_counter(void) now = time_interpolator_get_cycles(src); if (lcycle && time_after(lcycle, now)) return lcycle; + + /* When holding the xtime write lock, there's no need + * to add the overhead of the cmpxchg. Readers are + * force to retry until the write lock is released. + */ + if (writelock) { + time_interpolator->last_cycle = now; + return now; + } /* Keep track of the last timer value returned. The use of cmpxchg here * will cause contention in an SMP environment. */ @@ -1456,7 +1465,7 @@ static inline u64 time_interpolator_get_counter(void) void time_interpolator_reset(void) { time_interpolator->offset = 0; - time_interpolator->last_counter = time_interpolator_get_counter(); + time_interpolator->last_counter = time_interpolator_get_counter(1); } #define GET_TI_NSECS(count,i) (((((count) - i->last_counter) & (i)->mask) * (i)->nsec_per_cyc) >> (i)->shift) @@ -1468,7 +1477,7 @@ unsigned long time_interpolator_get_offset(void) return 0; return time_interpolator->offset + - GET_TI_NSECS(time_interpolator_get_counter(), time_interpolator); + GET_TI_NSECS(time_interpolator_get_counter(0), time_interpolator); } #define INTERPOLATOR_ADJUST 65536 @@ -1491,7 +1500,7 @@ static void time_interpolator_update(long delta_nsec) * and the tuning logic insures that. */ - counter = time_interpolator_get_counter(); + counter = time_interpolator_get_counter(1); offset = time_interpolator->offset + GET_TI_NSECS(counter, time_interpolator); if (delta_nsec < 0 || (unsigned long) delta_nsec < offset) |