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Better fix for the problem addressed by rev.1.79: don't loop in

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fifo_open() waiting for another reader or writer if one arrived and
departed while we were waiting (or a little earlier).

Rev.1.79 broke blocking opens of fifos by making them time out after 1
second.  This was bad for at least apsfilter.

Tested by:	"Simon 'corecode' Schubert" <corecode@corecode.ath.cx>,
		Alexander Leidinger <Alexander@leidinger.net>,
		phk
MFC after:	4 weeks
This commit is contained in:
Bruce Evans 2003-03-24 11:03:42 +00:00
parent aae483c597
commit 520cab0a32
1 changed files with 13 additions and 8 deletions
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21
sys/fs/fifofs/fifo_vnops.c
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@ -226,13 +226,18 @@ fifo_open(ap)
}
}
if ((ap->a_mode & FREAD) && (ap->a_mode & O_NONBLOCK) == 0) {
while (fip->fi_writers == 0) {
if (fip->fi_writers == 0) {
VOP_UNLOCK(vp, 0, td);
error = tsleep(&fip->fi_readers,
PCATCH | PSOCK, "fifoor", 0);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
if (error)
goto bad;
/*
* We must have got woken up because we had a writer.
* That (and not still having one) is the condition
* that we must wait for.
*/
}
}
if (ap->a_mode & FWRITE) {
@ -242,18 +247,18 @@ fifo_open(ap)
goto bad;
}
} else {
while (fip->fi_readers == 0) {
if (fip->fi_readers == 0) {
VOP_UNLOCK(vp, 0, td);
/*
* XXX: Some race I havn't located is solved
* by timing out after a sec. Race seen when
* sendmail hangs here during boot /phk
*/
error = tsleep(&fip->fi_writers,
PCATCH | PSOCK, "fifoow", hz);
PCATCH | PSOCK, "fifoow", 0);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
if (error)
goto bad;
/*
* We must have got woken up because we had
* a reader. That (and not still having one)
* is the condition that we must wait for.
*/
}
}
}