Messages in this thread Patch in this message | | | Date | Wed, 8 Oct 2003 11:58:20 -0700 | From | Stephen Hemminger <> | Subject | [PATCH] monotonic seqlock for HPET timer |
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Replace read/write lock used for HPET timer monotonic_lock with seqlock. Similar to locking used on xtime and monotonic_lock in timers/timer_tsc.c
It builds and runs, but I don't have hardware with HPET support to test. Not a big deal (yet) since only hangcheck timer uses monotonic clock so far.
diff -urN -X dontdiff linux-2.5/arch/i386/kernel/timers/timer_hpet.c linux-2.5-net/arch/i386/kernel/timers/timer_hpet.c --- linux-2.5/arch/i386/kernel/timers/timer_hpet.c 2003-09-30 13:53:48.000000000 -0700 +++ linux-2.5-net/arch/i386/kernel/timers/timer_hpet.c 2003-09-16 12:54:26.000000000 -0700 @@ -24,7 +24,7 @@ static unsigned long last_tsc_low; /* lsb 32 bits of Time Stamp Counter */ static unsigned long last_tsc_high; /* msb 32 bits of Time Stamp Counter */ static unsigned long long monotonic_base; -static rwlock_t monotonic_lock = RW_LOCK_UNLOCKED; +static seqlock_t monotonic_lock = SEQLOCK_UNLOCKED; /* convert from cycles(64bits) => nanoseconds (64bits) * basic equation: @@ -57,12 +57,14 @@ static unsigned long long monotonic_clock_hpet(void) { unsigned long long last_offset, this_offset, base; + unsigned seq; /* atomically read monotonic base & last_offset */ - read_lock_irq(&monotonic_lock); - last_offset = ((unsigned long long)last_tsc_high<<32)|last_tsc_low; - base = monotonic_base; - read_unlock_irq(&monotonic_lock); + do { + seq = read_seqbegin(&monotonic_lock); + last_offset = ((unsigned long long)last_tsc_high<<32)|last_tsc_low; + base = monotonic_base; + } while (read_seqretry(&monotonic_lock, seq)); /* Read the Time Stamp Counter */ rdtscll(this_offset); @@ -99,7 +101,7 @@ unsigned long long this_offset, last_offset; unsigned long offset; - write_lock(&monotonic_lock); + write_seqlock(&monotonic_lock); last_offset = ((unsigned long long)last_tsc_high<<32)|last_tsc_low; rdtsc(last_tsc_low, last_tsc_high); @@ -113,7 +115,7 @@ /* update the monotonic base value */ this_offset = ((unsigned long long)last_tsc_high<<32)|last_tsc_low; monotonic_base += cycles_2_ns(this_offset - last_offset); - write_unlock(&monotonic_lock); + write_sequnlock(&monotonic_lock); } void delay_hpet(unsigned long loops) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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