Dong Feng wrote:
2006/9/30, Christoph Lameter <[email protected]>:
On Fri, 29 Sep 2006, Dong Feng wrote:
> If the comments mean the subsequent code is SMP-safe and can prevent
> nest-kernel-path, how does it achieves that?
It relies on locking outside of do_sys_settimeofday(). Seems that this
indicates locking is to be performed by the arch before calling
do_sys_settimeofday. Looks suspicious to me. Check that this function is
always called with the same lock.
Yes, that is the question. The whole invocation path is
sys_settimeofday() -> do_sys_settimeofday()
I do not find a lock embracing do_sys_settimeofday().
Moreover, seems neither write operations nor read operations on sys_tz
is protected by any locks, in sys_gettimeofday() and
sys_settimeofday() respectively.
Did you get to the bottom of this yet? It looks like you're right,
and I suggest a seqlock might be a good option.
You should write a patch and send it to Mister Morton.
--
SUSE Labs, Novell Inc.
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