On 11.05.2006 [10:25:29 -0400], linux-os (Dick Johnson) wrote:
>
>
> Hello,
>
> I'm trying to fix a long-standing bug which has a
> work-around that has been working for a year or
> so.
<snip valiant efforts>
> Here is relevent code:
>
> for(;;) {
> mem->pfd.fd = fd;
> mem->pfd.events = POLLIN|POLLERR|POLLHUP|POLLNVAL;
> mem->pfd.revents = 0x00;
Hrm, in looking at the craziness that is sys_poll() for a bit, I think
it's the underlying f_ops that are responsible for not setting POLLHUP,
that is:
if (file != NULL) {
mask = DEFAULT_POLLMASK;
if (file->f_op && file->f_op->poll)
mask = file->f_op->poll(file, *pwait);
mask &= fdp->events | POLLERR | POLLHUP;
fput_light(file, fput_needed);
}
and file->f_op->poll(file, *pwait) is not setting POLLHUP on the
disconnect. What filesystem is this?
On an independent note, it seems like the relatively recent cleanups to
sys_poll() made the negative case a bit inefficient (and reliant on
msecs_to_jiffies() dealing with negative values, which I don't think it
was really ever designed to (it's mostly used for converting time
values, which can never go negative)). Maybe the following would make
sense? Peter, I know you had been looking at poll() issues earlier, does
this change make sense?
Description: Rather than make msecs_to_jiffies() deal with negative
values, just send them on to do_sys_poll(), which (eventually in
do_poll()) explicitly checks for them.
Signed-off-by: Nishanth Aravamudan <[email protected]>
diff -urpN 2.6.17-rc3-git18/fs/select.c 2.6.17-rc3-git18-dev/fs/select.c
--- 2.6.17-rc3-git18/fs/select.c 2006-05-11 12:17:15.000000000 -0700
+++ 2.6.17-rc3-git18-dev/fs/select.c 2006-05-11 12:38:16.000000000 -0700
@@ -727,9 +727,9 @@ out_fds:
asmlinkage long sys_poll(struct pollfd __user *ufds, unsigned int nfds,
long timeout_msecs)
{
- s64 timeout_jiffies = 0;
+ s64 timeout_jiffies;
- if (timeout_msecs) {
+ if (timeout_msecs > 0) {
#if HZ > 1000
/* We can only overflow if HZ > 1000 */
if (timeout_msecs / 1000 > (s64)0x7fffffffffffffffULL / (s64)HZ)
@@ -737,6 +737,8 @@ asmlinkage long sys_poll(struct pollfd _
else
#endif
timeout_jiffies = msecs_to_jiffies(timeout_msecs);
+ } else {
+ timeout_jiffies = timeout_msecs;
}
return do_sys_poll(ufds, nfds, &timeout_jiffies);
--
Nishanth Aravamudan <[email protected]>
IBM Linux Technology Center
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