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If more than one thread allocated sf buffers for sendfile(2), and

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each of the threads needs more while current pool of the buffers is
exhausted, then neither thread can make progress.

Switch to nowait allocations after we got first buffer already.

Reported by:	az
Reviewed by:	alc (previous version)
Tested by:	pho
MFC after:	1 week
This commit is contained in:
kib 2011-01-28 17:37:09 +00:00
parent 36a5448bf6
commit 42cc2c0d98
1 changed files with 12 additions and 5 deletions
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17
sys/kern/uipc_syscalls.c
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@ -2126,18 +2126,25 @@ kern_sendfile(struct thread *td, struct sendfile_args *uap,
}
/*
* Get a sendfile buf. We usually wait as long
* as necessary, but this wait can be interrupted.
* Get a sendfile buf. When allocating the
* first buffer for mbuf chain, we usually
* wait as long as necessary, but this wait
* can be interrupted. For consequent
* buffers, do not sleep, since several
* threads might exhaust the buffers and then
* deadlock.
*/
if ((sf = sf_buf_alloc(pg,
(mnw ? SFB_NOWAIT : SFB_CATCH))) == NULL) {
sf = sf_buf_alloc(pg, (mnw || m != NULL) ? SFB_NOWAIT :
SFB_CATCH);
if (sf == NULL) {
mbstat.sf_allocfail++;
vm_page_lock(pg);
vm_page_unwire(pg, 0);
KASSERT(pg->object != NULL,
("kern_sendfile: object disappeared"));
vm_page_unlock(pg);
error = (mnw ? EAGAIN : EINTR);
if (m == NULL)
error = (mnw ? EAGAIN : EINTR);
break;
}