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Only poll the fifo for read events if the fifo is attached to a readable

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file descriptor.  Otherwise, the read end of a fifo might return that it
is writable (which it isn't).

Only poll the fifo for write events if the fifo attached to a writable
file descriptor.  Otherwise, the write end of a fifo might return that
it is readable (which it isn't).

In the event that a file is FREAD|FWRITE (which is allowed by POSIX, but
has undefined behavior), we poll for both.

MFC after:	3 days
This commit is contained in:
Robert Watson 2005-09-12 10:16:18 +00:00
parent 845e8e827b
commit 6dd84b0bdc
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=150027
1 changed files with 2 additions and 2 deletions
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4
sys/fs/fifofs/fifo_vnops.c
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@ -615,7 +615,7 @@ fifo_poll_f(struct file *fp, int events, struct ucred *cred, struct thread *td)
fip = fp->f_data;
levents = events &
(POLLIN | POLLINIGNEOF | POLLPRI | POLLRDNORM | POLLRDBAND);
if (levents) {
if ((fp->f_flag & FREAD) && levents) {
/*
* If POLLIN or POLLRDNORM is requested and POLLINIGNEOF is
* not, then convert the first two to the last one. This
@ -641,7 +641,7 @@ fifo_poll_f(struct file *fp, int events, struct ucred *cred, struct thread *td)
}
}
levents = events & (POLLOUT | POLLWRNORM | POLLWRBAND);
if (levents) {
if ((fp->f_flag & FWRITE) && levents) {
filetmp.f_data = fip->fi_writesock;
filetmp.f_cred = cred;
if (filetmp.f_data) {