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arm64: vdso: remove broken, redundant sequence counting for timezones 

This patch is an arm64 version of ce73ec6db4 ("powerpc/vdso: Remove
redundant locking in update_vsyscall_tz()").

Timezone data is not protected, so the sequence counter is not required
to ensure consistency. Furthermore, having multiple paths updating the
counter leads to a race between update_vsyscall and update_vsyscall_tz,
so remove the timezone sequence counting from both the kernel and the
vdso.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Will Deacon 2013-01-07 16:12:31 +00:00 committed by Catalin Marinas
parent 9931faca02
commit bdba0051eb
2 changed files with 0 additions and 6 deletions
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4
arch/arm64/kernel/vdso.c
View File

@ -252,10 +252,6 @@ void update_vsyscall(struct timekeeper *tk)
void update_vsyscall_tz(void)
{
++vdso_data->tb_seq_count;
smp_wmb();
vdso_data->tz_minuteswest = sys_tz.tz_minuteswest;
vdso_data->tz_dsttime = sys_tz.tz_dsttime;
smp_wmb();
++vdso_data->tb_seq_count;
}

2
arch/arm64/kernel/vdso/gettimeofday.S
View File

@ -73,8 +73,6 @@ ENTRY(__kernel_gettimeofday)
/* If tz is NULL, return 0. */
cbz x1, 3f
ldp w4, w5, [vdso_data, #VDSO_TZ_MINWEST]
seqcnt_read w9
seqcnt_check w9, 1b
stp w4, w5, [x1, #TZ_MINWEST]
3:
mov x0, xzr