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Fix panic introduced by r235745. Panic occurs after first packet traverse renamed interface.

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Add several comments on locking

Found by:         avg
Approved by:      ae(mentor)
Tested by:        avg
MFC after:        1 week
This commit is contained in:
Alexander V. Chernikov 2012-06-04 12:36:58 +00:00
parent fbfb753fad
commit 784292f89a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=236559
1 changed files with 22 additions and 2 deletions
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24
sys/net/bpf.c
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@ -1704,6 +1704,14 @@ bpfioctl(struct cdev *dev, u_long cmd, caddr_t addr, int flags,
/*
* Set d's packet filter program to fp. If this file already has a filter,
* free it and replace it. Returns EINVAL for bogus requests.
*
* Note we need global lock here to serialize bpf_setf() and bpf_setif() calls
* since reading d->bd_bif can't be protected by d or interface lock due to
* lock order.
*
* Additionally, we have to acquire interface write lock due to bpf_mtap() uses
* interface read lock to read all filers.
*
*/
static int
bpf_setf(struct bpf_d *d, struct bpf_program *fp, u_long cmd)
@ -2535,20 +2543,32 @@ bpfdetach(struct ifnet *ifp)
}
/*
* Interface departure handler
* Interface departure handler.
* Note departure event does not guagantee interface is going down.
*/
static void
bpf_ifdetach(void *arg __unused, struct ifnet *ifp)
{
struct bpf_if *bp;
if ((bp = ifp->if_bpf) == NULL)
BPF_LOCK();
if ((bp = ifp->if_bpf) == NULL) {
BPF_UNLOCK();
return;
}
/* Check if bpfdetach() was called previously */
if ((bp->flags & BPFIF_FLAG_DYING) == 0) {
BPF_UNLOCK();
return;
}
CTR3(KTR_NET, "%s: freing BPF instance %p for interface %p",
__func__, bp, ifp);
ifp->if_bpf = NULL;
BPF_UNLOCK();
rw_destroy(&bp->bif_lock);
free(bp, M_BPF);
}