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ia64: vsyscall: Use seqcount instead of seqlock 

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>
Signed-off-by: John Stultz <john.stultz@linaro.org>
This commit is contained in:
Thomas Gleixner 2012-02-28 19:46:05 +00:00 committed by John Stultz
parent 2ab516575f
commit 74a622be3d
4 changed files with 7 additions and 11 deletions
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4
arch/ia64/kernel/asm-offsets.c
View File

@ -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,

2
arch/ia64/kernel/fsys.S
View File

@ -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

2
arch/ia64/kernel/fsyscall_gtod_data.h
View File

@ -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;

10
arch/ia64/kernel/time.c
View File

@ -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);
}