From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: John Stultz <john.stultz@linaro.org>, Ingo Molnar <mingo@elte.hu>,
Peter Anvin <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Tony Luck <tony.luck@intel.com>
Subject: [patch 4/4] ia64: vsyscall: Use seqcount instead of seqlock
Date: Tue, 28 Feb 2012 19:46:05 -0000 [thread overview]
Message-ID: <20120228194508.624811514@linutronix.de> (raw)
In-Reply-To: <20120228194200.180923135@linutronix.de>
[-- Attachment #1: ia64-vdso-use-seqcount.patch --]
[-- Type: text/plain, Size: 3071 bytes --]
The update of the vdso data happens under xtime_lock, so adding a
nested lock is pointless. Just use a seqcount to sync the readers.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
---
arch/ia64/kernel/asm-offsets.c | 4 ++--
arch/ia64/kernel/fsys.S | 2 +-
arch/ia64/kernel/fsyscall_gtod_data.h | 2 +-
arch/ia64/kernel/time.c | 10 +++-------
4 files changed, 7 insertions(+), 11 deletions(-)
Index: linux-2.6/arch/ia64/kernel/asm-offsets.c
===================================================================
--- linux-2.6.orig/arch/ia64/kernel/asm-offsets.c
+++ linux-2.6/arch/ia64/kernel/asm-offsets.c
@@ -269,8 +269,8 @@ void foo(void)
BLANK();
/* used by fsys_gettimeofday in arch/ia64/kernel/fsys.S */
- DEFINE(IA64_GTOD_LOCK_OFFSET,
- offsetof (struct fsyscall_gtod_data_t, lock));
+ DEFINE(IA64_GTOD_SEQ_OFFSET,
+ offsetof (struct fsyscall_gtod_data_t, seq);
DEFINE(IA64_GTOD_WALL_TIME_OFFSET,
offsetof (struct fsyscall_gtod_data_t, wall_time));
DEFINE(IA64_GTOD_MONO_TIME_OFFSET,
Index: linux-2.6/arch/ia64/kernel/fsys.S
===================================================================
--- linux-2.6.orig/arch/ia64/kernel/fsys.S
+++ linux-2.6/arch/ia64/kernel/fsys.S
@@ -174,7 +174,7 @@ ENTRY(fsys_set_tid_address)
FSYS_RETURN
END(fsys_set_tid_address)
-#if IA64_GTOD_LOCK_OFFSET !=0
+#if IA64_GTOD_SEQ_OFFSET !=0
#error fsys_gettimeofday incompatible with changes to struct fsyscall_gtod_data_t
#endif
#if IA64_ITC_JITTER_OFFSET !=0
Index: linux-2.6/arch/ia64/kernel/fsyscall_gtod_data.h
===================================================================
--- linux-2.6.orig/arch/ia64/kernel/fsyscall_gtod_data.h
+++ linux-2.6/arch/ia64/kernel/fsyscall_gtod_data.h
@@ -6,7 +6,7 @@
*/
struct fsyscall_gtod_data_t {
- seqlock_t lock;
+ seqcount_t seq;
struct timespec wall_time;
struct timespec monotonic_time;
cycle_t clk_mask;
Index: linux-2.6/arch/ia64/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/ia64/kernel/time.c
+++ linux-2.6/arch/ia64/kernel/time.c
@@ -35,9 +35,7 @@
static cycle_t itc_get_cycles(struct clocksource *cs);
-struct fsyscall_gtod_data_t fsyscall_gtod_data = {
- .lock = __SEQLOCK_UNLOCKED(fsyscall_gtod_data.lock),
-};
+struct fsyscall_gtod_data_t fsyscall_gtod_data;
struct itc_jitter_data_t itc_jitter_data;
@@ -460,9 +458,7 @@ void update_vsyscall_tz(void)
void update_vsyscall(struct timespec *wall, struct timespec *wtm,
struct clocksource *c, u32 mult)
{
- unsigned long flags;
-
- write_seqlock_irqsave(&fsyscall_gtod_data.lock, flags);
+ write_seqcount_begin(&fsyscall_gtod_data.seq);
/* copy fsyscall clock data */
fsyscall_gtod_data.clk_mask = c->mask;
@@ -485,6 +481,6 @@ void update_vsyscall(struct timespec *wa
fsyscall_gtod_data.monotonic_time.tv_sec++;
}
- write_sequnlock_irqrestore(&fsyscall_gtod_data.lock, flags);
+ write_seqcount_end(&fsyscall_gtod_data.seq);
}
next prev parent reply other threads:[~2012-02-28 19:46 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-28 19:46 [patch 0/4] time/timekeeping: Simplify vsyscall locking Thomas Gleixner
2012-02-28 19:46 ` [patch 1/4] time: Remove bogus comments Thomas Gleixner
2012-02-28 19:46 ` [patch 2/4] x86: vdso: Remove bogus locking in update_vsyscall_tz() Thomas Gleixner
2012-02-28 19:46 ` [patch 3/4] x86: vdso: Use seqcount instead of seqlock Thomas Gleixner
2012-02-28 19:46 ` Thomas Gleixner [this message]
2012-03-26 23:04 ` [patch 4/4] ia64: vsyscall: " Tony Luck
2012-03-27 13:05 ` Thomas Gleixner
2012-02-29 20:07 ` [patch 0/4] time/timekeeping: Simplify vsyscall locking Andy Lutomirski
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