arm64: vdso: check sequence counter even for coarse realtime operations
authorWill Deacon <will.deacon@arm.com>
Thu, 29 Nov 2012 22:11:51 +0000 (22:11 +0000)
committerCatalin Marinas <catalin.marinas@arm.com>
Wed, 5 Dec 2012 11:20:03 +0000 (11:20 +0000)
commitf84a935db47d7f261c025ba9eaa7700261257469
tree0df122141ab5862220184f5f6746038daf925cf3
parent251db45336c8fb5fd0c36f71aabc6950e427110f
arm64: vdso: check sequence counter even for coarse realtime operations

When returning coarse realtime values from clock_gettime, we must still
check the sequence counter to ensure that the kernel does not update
the vdso datapage whilst we are loading the coarse timespec as this
could potentially result in time appearing to go backwards.

This patch delays the coarse realtime check until after we have loaded
successfully from the vdso datapage. This does mean that we always load
the wtm timespec, but conditionalising the load and adding an extra
sequence test is unlikely to buy us anything other than messy code,
particularly as the sequence test implies a read barrier.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
arch/arm64/kernel/vdso/gettimeofday.S