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 _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
