Messages in this thread | | | Subject | RE: [PATCH] monotonic seqlock for HPET timer | Date | Wed, 8 Oct 2003 17:15:48 -0700 | From | "Pallipadi, Venkatesh" <> |
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Tested on HPET capable system. Works fine.
Thanks, -Venkatesh
> -----Original Message----- > From: linux-kernel-owner@vger.kernel.org > [mailto:linux-kernel-owner@vger.kernel.org] On Behalf Of > Stephen Hemminger > Sent: Wednesday, October 08, 2003 11:58 AM > To: john stultz; Linus Torvalds; Andrew Morton > Cc: linux-kernel@vger.kernel.org > Subject: [PATCH] monotonic seqlock for HPET timer > > > 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/ > - 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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