Date: Tue, 28 May 2019 11:45:00 +0000 (UTC) From: "Andrey V. Elsukov" <ae@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r348324 - head/sys/net Message-ID: <201905281145.x4SBj0Yj094548@repo.freebsd.org>
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Author: ae Date: Tue May 28 11:45:00 2019 New Revision: 348324 URL: https://svnweb.freebsd.org/changeset/base/348324 Log: Rework r348303 to reduce the time of holding global BPF lock. It appeared that using NET_EPOCH_WAIT() while holding global BPF lock can lead to another panic: spin lock 0xfffff800183c9840 (turnstile lock) held by 0xfffff80018e2c5a0 (tid 100325) too long panic: spin lock held too long ... #0 sched_switch (td=0xfffff80018e2c5a0, newtd=0xfffff8000389e000, flags=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2133 #1 0xffffffff80bf9912 in mi_switch (flags=256, newtd=0x0) at /usr/src/sys/kern/kern_synch.c:439 #2 0xffffffff80c21db7 in sched_bind (td=<optimized out>, cpu=<optimized out>) at /usr/src/sys/kern/sched_ule.c:2704 #3 0xffffffff80c34c33 in epoch_block_handler_preempt (global=<optimized out>, cr=0xfffffe00005a1a00, arg=<optimized out>) at /usr/src/sys/kern/subr_epoch.c:394 #4 0xffffffff803c741b in epoch_block (global=<optimized out>, cr=<optimized out>, cb=<optimized out>, ct=<optimized out>) at /usr/src/sys/contrib/ck/src/ck_epoch.c:416 #5 ck_epoch_synchronize_wait (global=0xfffff8000380cd80, cb=<optimized out>, ct=<optimized out>) at /usr/src/sys/contrib/ck/src/ck_epoch.c:465 #6 0xffffffff80c3475e in epoch_wait_preempt (epoch=0xfffff8000380cd80) at /usr/src/sys/kern/subr_epoch.c:513 #7 0xffffffff80ce970b in bpf_detachd_locked (d=0xfffff801d309cc00, detached_ifp=<optimized out>) at /usr/src/sys/net/bpf.c:856 #8 0xffffffff80ced166 in bpf_detachd (d=<optimized out>) at /usr/src/sys/net/bpf.c:836 #9 bpf_dtor (data=0xfffff801d309cc00) at /usr/src/sys/net/bpf.c:914 To fix this add the check to the catchpacket() that BPF descriptor was not detached just before we acquired BPFD_LOCK(). Reported by: slavash Tested by: slavash MFC after: 1 week Modified: head/sys/net/bpf.c Modified: head/sys/net/bpf.c ============================================================================== --- head/sys/net/bpf.c Tue May 28 10:55:59 2019 (r348323) +++ head/sys/net/bpf.c Tue May 28 11:45:00 2019 (r348324) @@ -850,15 +850,10 @@ bpf_detachd_locked(struct bpf_d *d, bool detached_ifp) /* Check if descriptor is attached */ if ((bp = d->bd_bif) == NULL) return; - /* - * Remove d from the interface's descriptor list. - * And wait until bpf_[m]tap*() will finish their possible work - * with descriptor. - */ - CK_LIST_REMOVE(d, bd_next); - NET_EPOCH_WAIT(); BPFD_LOCK(d); + /* Remove d from the interface's descriptor list. */ + CK_LIST_REMOVE(d, bd_next); /* Save bd_writer value */ error = d->bd_writer; ifp = bp->bif_ifp; @@ -2494,6 +2489,11 @@ catchpacket(struct bpf_d *d, u_char *pkt, u_int pktlen int tstype; BPFD_LOCK_ASSERT(d); + if (d->bd_bif == NULL) { + /* Descriptor was detached in concurrent thread */ + counter_u64_add(d->bd_dcount, 1); + return; + } /* * Detect whether user space has released a buffer back to us, and if
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