Re: [PATCH] Describe race of direct read and fork for unaligned buffers
From: Nick Piggin
Date: Tue May 08 2012 - 19:10:53 EST
On 6 May 2012 01:29, KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxx> wrote:
>> So, am I correct to assume that right text to add to the page is as below?
>> Nick, can you clarify what you mean by "quiesced"?
Yes exactly. That might be a simpler word. Thanks!
>> O_DIRECT IOs should never be run concurrently with fork(2) system call,
>> when the memory buffer is anonymous memory, or comes from mmap(2)
>> with MAP_PRIVATE.
>> Any such IOs, whether submitted with asynchronous IO interface or from
>> another thread in the process, should be quiesced before fork(2) is called.
>> Failure to do so can result in data corruption and undefined behavior in
>> parent and child processes.
>> This restriction does not apply when the memory buffer for the O_DIRECT
>> IOs comes from mmap(2) with MAP_SHARED or from shmat(2).
>> Nor does this restriction apply when the memory buffer has been advised
>> as MADV_DONTFORK with madvise(2), ensuring that it will not be available
>> to the child after fork(2).
> I don't have good English and I can't make editorial check. But at least,
> I don't find any technical incorrect explanation here.
> ÂAcked-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
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