2006/9/30, Christoph Lameter <[email protected]>:
On Fri, 29 Sep 2006, Dong Feng wrote:
> For my understanding, an assignment between structs should be a
> bit-wise copy. Such operation is not atomic, so it can not be supposed
Byte or Machine word yes.
> SMP-safe. And the subsequent test-and-assign operation on firsttime is
> not atomic, either.
No its not atomic on its own. Correct.
> 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.
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