On Jan 9, 2013, at 2:35 PM, John Baldwin <j...@freebsd.org> wrote:
> On Tuesday, November 13, 2012 4:40:57 pm Guy Helmer wrote:
>> To try to completely resolve the race in bpfread(), I have put together
> these changes to add a flag to indicate when the hold buffer cannot be
> modified because it is in use. Since it's my first time using mtx_sleep() and
> wakeup(), I wanted to run these past the list to see if I can get any
> feedback
> on the approach.
>>
>>
>> Index: bpf.c
>> ===================================================================
>> --- bpf.c (revision 242997)
>> +++ bpf.c (working copy)
>> @@ -819,6 +819,7 @@ bpfopen(struct cdev *dev, int flags, int fmt, stru
>> * particular buffer method.
>> */
>> bpf_buffer_init(d);
>> + d->bd_hbuf_in_use = 0;
>> d->bd_bufmode = BPF_BUFMODE_BUFFER;
>> d->bd_sig = SIGIO;
>> d->bd_direction = BPF_D_INOUT;
>> @@ -872,6 +873,9 @@ bpfread(struct cdev *dev, struct uio *uio, int iof
>> callout_stop(&d->bd_callout);
>> timed_out = (d->bd_state == BPF_TIMED_OUT);
>> d->bd_state = BPF_IDLE;
>> + while (d->bd_hbuf_in_use)
>> + mtx_sleep(&d->bd_hbuf_in_use, &d->bd_lock,
>> + PRINET|PCATCH, "bd_hbuf", 0);
>
> You need to check the return value here, otherwise the PCATCH is useless (you
> will just go back to sleep instead of failing with an error if this is
> interrupted by a signal).
Thanks for the feedback (sorry it's taken so long to get to it). Would this
change correctly handle interruptions?
Index: bpf.c
===================================================================
--- bpf.c (revision 250941)
+++ bpf.c (working copy)
@@ -856,9 +856,14 @@
callout_stop(&d->bd_callout);
timed_out = (d->bd_state == BPF_TIMED_OUT);
d->bd_state = BPF_IDLE;
- while (d->bd_hbuf_in_use)
- mtx_sleep(&d->bd_hbuf_in_use, &d->bd_lock,
+ while (d->bd_hbuf_in_use) {
+ error = mtx_sleep(&d->bd_hbuf_in_use, &d->bd_lock,
PRINET|PCATCH, "bd_hbuf", 0);
+ if (error == EINTR || error == ERESTART) {
+ BPFD_UNLOCK(d);
+ return (error);
+ }
+ }
/*
* If the hold buffer is empty, then do a timed sleep, which
* ends when the timeout expires or when enough packets
_______________________________________________
freebsd-net@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-net
To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
