From: Stephen Hemminger <shemminger@osdl.org>
To: Andrew Morton <akpm@osdl.org>
Cc: john stultz <johnstul@us.ibm.com>,
"Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] use seq_lock for monotonic time
Date: Tue, 16 Sep 2003 14:00:01 -0700 [thread overview]
Message-ID: <20030916140001.7027d6e5.shemminger@osdl.org> (raw)
In-Reply-To: <20030916115935.64ebce3d.akpm@osdl.org>
On Tue, 16 Sep 2003 11:59:35 -0700
Andrew Morton <akpm@osdl.org> 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)
next prev parent reply other threads:[~2003-09-16 21:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-09-16 17:27 Stephen Hemminger
[not found] ` <20030916115935.64ebce3d.akpm@osdl.org>
2003-09-16 21:00 ` Stephen Hemminger [this message]
2003-09-16 21:17 ` john stultz
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