Multiple concurrent write() by different thread is possible, as they all can share the same file descriptor in a single similar process, and this is not allowed. So nevertheless, the problem you posed is not allowed/acceptable by the kernel, so Linus himself fixed it:
See here:
And Linus patch:
but my present version (3.2.0) has rcu lock over it (higher performance):
INIT_LIST_HEAD(&f->f_u.fu_list);
atomic_long_set(&f->f_count, 1);
rwlock_init(&f->f_owner.lock);
spin_lock_init(&f->f_lock);
eventpoll_init_file(f);
/* f->f_version: 0 */
On Thu, Feb 7, 2013 at 4:44 PM, Karaoui mohamed lamine <moharaka@xxxxxxxxx> wrote:
Tahnks guys!2013/1/30 Karaoui mohamed lamine <moharaka@xxxxxxxxx>thanks, i think i get it.2013/1/30 <Valdis.Kletnieks@xxxxxx>On Tue, 29 Jan 2013 20:16:26 +0100, you said:If you have non-overlapping writes, the kernel will eventually sort it out
> Actually my question is :
> Does POSIX specifies the fact that we need to use "lockf" to be able to do
> read/write operation in different offset ? Is'n the kernel supposed to
> ensure this ?
for you. If your writes overlap, you'll have to provide your own locking
via lockf() or similar, and synchronization via other methods.
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Regards,
Peter Teoh
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