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The pipe_poll() performs lockless access to the vnode to test

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fifo_iseof() condition, allowing the v_fifoinfo to be reset and freed
by fifo_cleanup().

Precalculate EOF at the places were fo_wgen is changed, and cache the
state in a new pipe state flag PIPE_SAMEWGEN.

Reported and tested by:	bf
Submitted by:	gianni
MFC after:	1 week (a backport)
This commit is contained in:
Konstantin Belousov 2012-03-07 07:31:50 +00:00
parent cd613b6351
commit f950879e16
4 changed files with 14 additions and 15 deletions
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1
sys/fs/fifofs/fifo.h
View File

@ -33,7 +33,6 @@
/*
* Prototypes for fifo operations on vnodes.
*/
int fifo_iseof(struct file *);
int fifo_vnoperate(struct vop_generic_args *);
int fifo_printinfo(struct vnode *);

25
sys/fs/fifofs/fifo_vnops.c
View File

@ -67,8 +67,16 @@ struct fifoinfo {
long fi_readers;
long fi_writers;
int fi_wgen;
int fi_seqcount;
};
#define FIFO_UPDWGEN(fip, pip) do { \
if ((fip)->fi_wgen == (fip)->fi_seqcount) \
(pip)->pipe_state |= PIPE_SAMEWGEN; \
else \
(pip)->pipe_state &= ~PIPE_SAMEWGEN; \
} while (0)
static vop_print_t fifo_print;
static vop_open_t fifo_open;
static vop_close_t fifo_close;
@ -174,7 +182,8 @@ fifo_open(ap)
if (fip->fi_writers > 0)
wakeup(&fip->fi_writers);
}
fp->f_seqcount = fip->fi_wgen - fip->fi_writers;
fip->fi_seqcount = fip->fi_wgen - fip->fi_writers;
FIFO_UPDWGEN(fip, fpipe);
}
if (ap->a_mode & FWRITE) {
if ((ap->a_mode & O_NONBLOCK) && fip->fi_readers == 0) {
@ -228,6 +237,7 @@ fifo_open(ap)
if (fpipe->pipe_state & PIPE_WANTR)
wakeup(fpipe);
fip->fi_wgen++;
FIFO_UPDWGEN(fip, fpipe);
PIPE_UNLOCK(fpipe);
fifo_cleanup(vp);
}
@ -287,6 +297,7 @@ fifo_close(ap)
if (cpipe->pipe_state & PIPE_WANTR)
wakeup(cpipe);
fip->fi_wgen++;
FIFO_UPDWGEN(fip, cpipe);
PIPE_UNLOCK(cpipe);
}
}
@ -373,15 +384,3 @@ fifo_advlock(ap)
return (ap->a_flags & F_FLOCK ? EOPNOTSUPP : EINVAL);
}
int
fifo_iseof(struct file *fp)
{
struct fifoinfo *fip;
KASSERT(fp->f_vnode != NULL, ("fifo_iseof: no vnode info"));
KASSERT(fp->f_vnode->v_fifoinfo != NULL, ("fifo_iseof: no fifoinfo"));
fip = fp->f_vnode->v_fifoinfo;
PIPE_LOCK_ASSERT(fip->fi_pipe, MA_OWNED);
return (fp->f_seqcount == fip->fi_wgen);
}

2
sys/kern/sys_pipe.c
View File

@ -1430,7 +1430,7 @@ pipe_poll(fp, events, active_cred, td)
levents = events &
(POLLIN | POLLINIGNEOF | POLLPRI | POLLRDNORM | POLLRDBAND);
if (rpipe->pipe_state & PIPE_NAMED && fp->f_flag & FREAD && levents &&
fifo_iseof(fp))
rpipe->pipe_state & PIPE_SAMEWGEN)
events |= POLLINIGNEOF;
if ((events & POLLINIGNEOF) == 0) {

1
sys/sys/pipe.h
View File

@ -96,6 +96,7 @@ struct pipemapping {
#define PIPE_DIRECTW 0x400 /* Pipe direct write active. */
#define PIPE_DIRECTOK 0x800 /* Direct mode ok. */
#define PIPE_NAMED 0x1000 /* Is a named pipe. */
#define PIPE_SAMEWGEN 0x2000 /* same write generation for named pipes. */
/*
* Per-pipe data structure.