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authorWill Deacon <will.deacon@arm.com>2013-01-07 16:12:31 +0000
committerCatalin Marinas <catalin.marinas@arm.com>2013-01-10 10:43:43 +0000
commitbdba0051ebcb3c6372f9cc0b2524c47cc6ce46fd (patch)
tree38efe063fe3fc5516e3a372a5d7908a9a5f2bf5d
parent9931faca02c604c22335f5a935a501bb2ace6e20 (diff)
downloadop-kernel-dev-bdba0051ebcb3c6372f9cc0b2524c47cc6ce46fd.zip
op-kernel-dev-bdba0051ebcb3c6372f9cc0b2524c47cc6ce46fd.tar.gz
arm64: vdso: remove broken, redundant sequence counting for timezones
This patch is an arm64 version of ce73ec6db47a ("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>
-rw-r--r--arch/arm64/kernel/vdso.c4
-rw-r--r--arch/arm64/kernel/vdso/gettimeofday.S2
2 files changed, 0 insertions, 6 deletions
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index c958cb8..6a389dc 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -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;
}
diff --git a/arch/arm64/kernel/vdso/gettimeofday.S b/arch/arm64/kernel/vdso/gettimeofday.S
index 8bf658d..f0a6d10 100644
--- a/arch/arm64/kernel/vdso/gettimeofday.S
+++ b/arch/arm64/kernel/vdso/gettimeofday.S
@@ -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
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