Date: Mon, 13 May 2019 18:09:59 -0400 From: Li-Wen Hsu <lwhsu@freebsd.org> To: Mark Johnston <markj@freebsd.org> Cc: "Andrey V. Elsukov" <ae@freebsd.org>, src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org, melifaro@freebsd.org Subject: Re: svn commit: r347526 - head/sys/net Message-ID: <CAKBkRUxDftmT-35P4uPxpF7QtDkLjMGyJewGR-pcV%2BfjdzJByw@mail.gmail.com> In-Reply-To: <20190513193754.GA37655@raichu> References: <201905131345.x4DDjTRn092669@repo.freebsd.org> <20190513193754.GA37655@raichu>
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On Mon, May 13, 2019 at 3:38 PM Mark Johnston <markj@freebsd.org> wrote: > > On Mon, May 13, 2019 at 01:45:29PM +0000, Andrey V. Elsukov wrote: > > Author: ae > > Date: Mon May 13 13:45:28 2019 > > New Revision: 347526 > > URL: https://svnweb.freebsd.org/changeset/base/347526 > > > > Log: > > Rework locking in BPF code to remove rwlock from fast path. > > > > On high packets rate the contention on rwlock in bpf_*tap*() functions > > can lead to packets dropping. To avoid this, migrate this code to use > > epoch(9) KPI and ConcurrencyKit's lists. > > > > * all lists changed to use CK_LIST; > > * reference counting added to bpf_if and bpf_d; > > * now bpf_if references ifnet and releases this reference on destroy; > > * each bpf_d descriptor references bpf_if when it is attached; > > * new struct bpf_program_buffer introduced to keep BPF filter programs; > > * bpf_program_buffer, bpf_d and bpf_if structures are freed by > > epoch_call(); > > * bpf_freelist and ifnet_departure event are no longer needed, thus > > both are removed; > > > > Reviewed by: melifaro > > Sponsored by: Yandex LLC > > Differential Revision: https://reviews.freebsd.org/D20224 > > This seems to introduce a possible recursion on the bpf cdev mutex. Now > bpfwrite() holds the mutex over the if_output call, which may enter > bpf_mtap() via bridge_transmit(), and bpf_mtap() may attempt to > reacquire the mutex. It does, the sys.netinet.fibs_test.arpresolve_checks_interface_fib case can trigger a panic: root@:/usr/tests/sys/netinet # kyua test fibs_test:arpresolve_checks_interface_fib fibs_test:arpresolve_checks_interface_fib -> panic: _mtx_lock_sleep: recursed on non-recursive mutex bpf @ /usr/src/sys/net/bpf.c:2325
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