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Subject[PATCH RT 09/25][RFC 3.0.23-rt39-rc1] ia64: vsyscall: Use seqcount instead of seqlock
From: Thomas Gleixner <tglx@linutronix.de>

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>
Cc: stable-rt@vger.kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
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(-)
diff --git a/arch/ia64/kernel/asm-offsets.c b/arch/ia64/kernel/asm-offsets.c
index af56501..106aeb6 100644
--- a/arch/ia64/kernel/asm-offsets.c
+++ b/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,
diff --git a/arch/ia64/kernel/fsys.S b/arch/ia64/kernel/fsys.S
index 331d42b..fa77de7 100644
--- a/arch/ia64/kernel/fsys.S
+++ b/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
diff --git a/arch/ia64/kernel/fsyscall_gtod_data.h b/arch/ia64/kernel/fsyscall_gtod_data.h
index 57d2ee6..146b15b 100644
--- a/arch/ia64/kernel/fsyscall_gtod_data.h
+++ b/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;
diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
index 85118df..15823ed 100644
--- a/arch/ia64/kernel/time.c
+++ b/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 *wall, struct timespec *wtm,
fsyscall_gtod_data.monotonic_time.tv_sec++;
}

- write_sequnlock_irqrestore(&fsyscall_gtod_data.lock, flags);
+ write_seqcount_end(&fsyscall_gtod_data.seq);
}

--
1.7.8.3



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