svn commit: r348324 - head/sys/net
Gleb Smirnoff
glebius at freebsd.org
Wed May 29 00:14:18 UTC 2019
Hi,
sorry for short followup, replied on previous commit without
reading through whole mailbox. Given the fallout of r348303
I'd suggest to consider my one liner as a proper solution to
the problem.
On Tue, May 28, 2019 at 11:45:00AM +0000, Andrey V. Elsukov wrote:
A> Author: ae
A> Date: Tue May 28 11:45:00 2019
A> New Revision: 348324
A> URL: https://svnweb.freebsd.org/changeset/base/348324
A>
A> Log:
A> Rework r348303 to reduce the time of holding global BPF lock.
A>
A> It appeared that using NET_EPOCH_WAIT() while holding global BPF lock
A> can lead to another panic:
A>
A> spin lock 0xfffff800183c9840 (turnstile lock) held by 0xfffff80018e2c5a0 (tid 100325) too long
A> panic: spin lock held too long
A> ...
A> #0 sched_switch (td=0xfffff80018e2c5a0, newtd=0xfffff8000389e000, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2133
A> #1 0xffffffff80bf9912 in mi_switch (flags=256, newtd=0x0) at /usr/src/sys/kern/kern_synch.c:439
A> #2 0xffffffff80c21db7 in sched_bind (td=<optimized out>, cpu=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2704
A> #3 0xffffffff80c34c33 in epoch_block_handler_preempt (global=<optimized out>, cr=0xfffffe00005a1a00, arg=<optimized out>)
A> at /usr/src/sys/kern/subr_epoch.c:394
A> #4 0xffffffff803c741b in epoch_block (global=<optimized out>, cr=<optimized out>, cb=<optimized out>, ct=<optimized out>)
A> at /usr/src/sys/contrib/ck/src/ck_epoch.c:416
A> #5 ck_epoch_synchronize_wait (global=0xfffff8000380cd80, cb=<optimized out>, ct=<optimized out>) at /usr/src/sys/contrib/ck/src/ck_epoch.c:465
A> #6 0xffffffff80c3475e in epoch_wait_preempt (epoch=0xfffff8000380cd80) at /usr/src/sys/kern/subr_epoch.c:513
A> #7 0xffffffff80ce970b in bpf_detachd_locked (d=0xfffff801d309cc00, detached_ifp=<optimized out>) at /usr/src/sys/net/bpf.c:856
A> #8 0xffffffff80ced166 in bpf_detachd (d=<optimized out>) at /usr/src/sys/net/bpf.c:836
A> #9 bpf_dtor (data=0xfffff801d309cc00) at /usr/src/sys/net/bpf.c:914
A>
A> To fix this add the check to the catchpacket() that BPF descriptor was
A> not detached just before we acquired BPFD_LOCK().
A>
A> Reported by: slavash
A> Tested by: slavash
A> MFC after: 1 week
A>
A> Modified:
A> head/sys/net/bpf.c
A>
A> Modified: head/sys/net/bpf.c
A> ==============================================================================
A> --- head/sys/net/bpf.c Tue May 28 10:55:59 2019 (r348323)
A> +++ head/sys/net/bpf.c Tue May 28 11:45:00 2019 (r348324)
A> @@ -850,15 +850,10 @@ bpf_detachd_locked(struct bpf_d *d, bool detached_ifp)
A> /* Check if descriptor is attached */
A> if ((bp = d->bd_bif) == NULL)
A> return;
A> - /*
A> - * Remove d from the interface's descriptor list.
A> - * And wait until bpf_[m]tap*() will finish their possible work
A> - * with descriptor.
A> - */
A> - CK_LIST_REMOVE(d, bd_next);
A> - NET_EPOCH_WAIT();
A>
A> BPFD_LOCK(d);
A> + /* Remove d from the interface's descriptor list. */
A> + CK_LIST_REMOVE(d, bd_next);
A> /* Save bd_writer value */
A> error = d->bd_writer;
A> ifp = bp->bif_ifp;
A> @@ -2494,6 +2489,11 @@ catchpacket(struct bpf_d *d, u_char *pkt, u_int pktlen
A> int tstype;
A>
A> BPFD_LOCK_ASSERT(d);
A> + if (d->bd_bif == NULL) {
A> + /* Descriptor was detached in concurrent thread */
A> + counter_u64_add(d->bd_dcount, 1);
A> + return;
A> + }
A>
A> /*
A> * Detect whether user space has released a buffer back to us, and if
A>
--
Gleb Smirnoff
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