Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262502AbTIPVC0 (ORCPT ); Tue, 16 Sep 2003 17:02:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262505AbTIPVC0 (ORCPT ); Tue, 16 Sep 2003 17:02:26 -0400 Received: from fw.osdl.org ([65.172.181.6]:12942 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S262502AbTIPVCW (ORCPT ); Tue, 16 Sep 2003 17:02:22 -0400 Date: Tue, 16 Sep 2003 14:00:01 -0700 From: Stephen Hemminger To: Andrew Morton Cc: john stultz , "Pallipadi, Venkatesh" , linux-kernel@vger.kernel.org Subject: Re: [PATCH] use seq_lock for monotonic time Message-Id: <20030916140001.7027d6e5.shemminger@osdl.org> In-Reply-To: <20030916115935.64ebce3d.akpm@osdl.org> References: <20030916102706.26bc4516.shemminger@osdl.org> <20030916115935.64ebce3d.akpm@osdl.org> Organization: Open Source Development Lab X-Mailer: Sylpheed version 0.9.4claws (GTK+ 1.2.10; i686-pc-linux-gnu) X-Face: &@E+xe?c%:&e4D{>f1O<&U>2qwRREG5!}7R4;D<"NO^UI2mJ[eEOA2*3>(`Th.yP,VDPo9$ /`~cw![cmj~~jWe?AHY7D1S+\}5brN0k*NE?pPh_'_d>6;XGG[\KDRViCfumZT3@[ Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4039 Lines: 112 On Tue, 16 Sep 2003 11:59:35 -0700 Andrew Morton wrote: > > So timer_cyclone and timer_hpet need the same change? Yes. diff -Nru a/arch/i386/kernel/timers/timer_cyclone.c b/arch/i386/kernel/timers/timer_cyclone.c --- a/arch/i386/kernel/timers/timer_cyclone.c Tue Sep 16 13:59:54 2003 +++ b/arch/i386/kernel/timers/timer_cyclone.c Tue Sep 16 13:59:54 2003 @@ -35,7 +35,7 @@ static u32 last_cyclone_low; static u32 last_cyclone_high; static unsigned long long monotonic_base; -static rwlock_t monotonic_lock = RW_LOCK_UNLOCKED; +static seqlock_t monotonic_lock = SEQLOCK_UNLOCKED; /* helper macro to atomically read both cyclone counter registers */ #define read_cyclone_counter(low,high) \ @@ -51,7 +51,7 @@ int count; unsigned long long this_offset, last_offset; - write_lock(&monotonic_lock); + write_seqlock(&monotonic_lock); last_offset = ((unsigned long long)last_cyclone_high<<32)|last_cyclone_low; spin_lock(&i8253_lock); @@ -76,7 +76,7 @@ /* update the monotonic base value */ this_offset = ((unsigned long long)last_cyclone_high<<32)|last_cyclone_low; monotonic_base += (this_offset - last_offset) & CYCLONE_TIMER_MASK; - write_unlock(&monotonic_lock); + write_sequnlock(&monotonic_lock); /* calculate delay_at_last_interrupt */ count = ((LATCH-1) - count) * TICK_SIZE; @@ -117,12 +117,15 @@ u32 now_low, now_high; unsigned long long last_offset, this_offset, base; unsigned long long ret; + unsigned seq; /* atomically read monotonic base & last_offset */ - read_lock_irq(&monotonic_lock); - last_offset = ((unsigned long long)last_cyclone_high<<32)|last_cyclone_low; - base = monotonic_base; - read_unlock_irq(&monotonic_lock); + do { + seq = read_seqbegin(&monotonic_lock); + last_offset = ((unsigned long long)last_cyclone_high<<32)|last_cyclone_low; + base = monotonic_base; + } while (read_seqretry(&monotonic_lock, seq)); + /* Read the cyclone counter */ read_cyclone_counter(now_low,now_high); diff -Nru a/arch/i386/kernel/timers/timer_hpet.c b/arch/i386/kernel/timers/timer_hpet.c --- a/arch/i386/kernel/timers/timer_hpet.c Tue Sep 16 13:59:54 2003 +++ b/arch/i386/kernel/timers/timer_hpet.c Tue Sep 16 13:59:54 2003 @@ -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/