Date: Tue, 12 Nov 2024 15:35:55 -0300 From: Jose Luis Duran <jlduran@freebsd.org> To: Cy Schubert <Cy.Schubert@cschubert.com> Cc: John Baldwin <jhb@freebsd.org>, src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 1fa6daaafd74 - main - ipfilter: Avoid stopping with a lock held Message-ID: <CAPwQLccpVdjUKQbCVQ0Vg5yRnmYSeKh%2Bb%2BThJwQY=z8OCZGOAw@mail.gmail.com> In-Reply-To: <20241112160243.B372532F@slippy.cwsent.com> References: <202411120347.4AC3lPOA015167@gitrepo.freebsd.org> <09923ad3-4065-4a31-b35f-74f84e09cff1@FreeBSD.org> <20241112155219.2E15A2DF@slippy.cwsent.com> <20241112160243.B372532F@slippy.cwsent.com>
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What would be the recommended approach in this case? Revert, and commit with the fixes, or just fix the problematic code. At any rate, I have created https://reviews.freebsd.org/D47530. Feel free to commandeer it, as my testing is limited to what's currently in the "Test Plan". I was not able to recreate the deadlock described here, but it definitely makes sense. On Tue, Nov 12, 2024 at 1:02=E2=80=AFPM Cy Schubert <Cy.Schubert@cschubert.= com> wrote: > > In message <20241112155219.2E15A2DF@slippy.cwsent.com>, Cy Schubert write= s: > > In message <09923ad3-4065-4a31-b35f-74f84e09cff1@FreeBSD.org>, John Bal= dwin > > wri > > tes: > > > On 11/11/24 19:47, Jose Luis Duran wrote: > > > > The branch main has been updated by jlduran: > > > > > > > > URL: https://cgit.FreeBSD.org/src/commit/?id=3D1fa6daaafd74c1a457dc= fe26e0a5 > > 94 > > > 3b5441dc9d > > > > > > > > commit 1fa6daaafd74c1a457dcfe26e0a5943b5441dc9d > > > > Author: Jose Luis Duran <jlduran@FreeBSD.org> > > > > AuthorDate: 2024-11-02 17:58:59 +0000 > > > > Commit: Jose Luis Duran <jlduran@FreeBSD.org> > > > > CommitDate: 2024-11-12 03:46:15 +0000 > > > > > > > > ipfilter: Avoid stopping with a lock held > > > > > > > > Avoid calling _callout_stop_safe with a non-sleepable lock hel= d when > > > > detaching by initializing callout_init_rw() with CALLOUT_SHARE= DLOCK. > > > > > > > > It avoids the following WITNESS warning when stopping the serv= ice: > > > > > > > > # service ipfilter stop > > > > calling _callout_stop_safe with the following non-sleepabl= e lock > > s > > > held: > > > > shared rw ipf filter load/unload mutex (ipf filter load/un= load m > > ut > > > ex) r =3D 0 (0xffff0000417c7530) locked @ /usr/src/sys/netpfil/ipfilt= er/netin > > et > > > /fil.c:7926 > > > > stack backtrace: > > > > #0 0xffff00000052d394 at witness_debugger+0x60 > > > > #1 0xffff00000052e620 at witness_warn+0x404 > > > > #2 0xffff0000004d4ffc at _callout_stop_safe+0x8c > > > > #3 0xffff0000f7236674 at ipfdetach+0x3c > > > > #4 0xffff0000f723fa4c at ipf_ipf_ioctl+0x788 > > > > #5 0xffff0000f72367e0 at ipfioctl+0x144 > > > > #6 0xffff00000034abd8 at devfs_ioctl+0x100 > > > > #7 0xffff0000005c66a0 at vn_ioctl+0xbc > > > > #8 0xffff00000034b2cc at devfs_ioctl_f+0x24 > > > > #9 0xffff0000005331ec at kern_ioctl+0x2e0 > > > > #10 0xffff000000532eb4 at sys_ioctl+0x140 > > > > #11 0xffff000000880480 at do_el0_sync+0x604 > > > > #12 0xffff0000008579ac at handle_el0_sync+0x4c > > > > > > > > PR: 282478 > > > > Suggested by: markj > > > > Reviewed by: cy > > > > Approved by: emaste (mentor) > > > > MFC after: 1 week > > > > --- > > > > sys/netpfil/ipfilter/netinet/ip_fil_freebsd.c | 4 ++-- > > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/sys/netpfil/ipfilter/netinet/ip_fil_freebsd.c b/sys/ne= tpfil/ > > ip > > > filter/netinet/ip_fil_freebsd.c > > > > index bcde0d2c7323..b3dea40c3d8c 100644 > > > > --- a/sys/netpfil/ipfilter/netinet/ip_fil_freebsd.c > > > > +++ b/sys/netpfil/ipfilter/netinet/ip_fil_freebsd.c > > > > @@ -181,7 +181,7 @@ ipf_timer_func(void *arg) > > > > #if 0 > > > > softc->ipf_slow_ch =3D timeout(ipf_timer_func, so= ftc, hz/ > > 2); > > > > #endif > > > > - callout_init(&softc->ipf_slow_ch, 1); > > > > + callout_init_rw(&softc->ipf_slow_ch, &softc->ipf_global.i= pf_lk, > > > CALLOUT_SHAREDLOCK); > > > > callout_reset(&softc->ipf_slow_ch, > > > > (hz / IPF_HZ_DIVIDE) * IPF_HZ_MULT, > > > > ipf_timer_func, softc); > > > > @@ -221,7 +221,7 @@ ipfattach(ipf_main_softc_t *softc) > > > > softc->ipf_slow_ch =3D timeout(ipf_timer_func, softc, > > > > (hz / IPF_HZ_DIVIDE) * IPF_H= Z_MULT > > ); > > > > #endif > > > > - callout_init(&softc->ipf_slow_ch, 1); > > > > + callout_init_rw(&softc->ipf_slow_ch, &softc->ipf_global.ipf_lk, C= ALLOUT > > > _SHAREDLOCK); > > > > callout_reset(&softc->ipf_slow_ch, (hz / IPF_HZ_DIVIDE) *= IPF_H > > Z_MULT, > > > > ipf_timer_func, softc); > > > > return (0); > > > > > > But this means the callout is now called with the lock held, and I do= n't se > > e > > > any changes > > > to ipf_timer_func. Hmm, so you now recurse on the lock? You need to= take > > ou > > > t the locking > > > in ipf_timer_func I think as it is now spurious. You can also axe th= e #if > > 0' > > > d code around > > > timeout() while you are at it. > > > > Reviewing all the #if 0's in ipfilter, discovering why they are there, = and > > either removing them or implementing what Darren had initially intended= is > > in my queue. The upstream git log isn't helpful for reasons I preach ab= out > > proper commit logs. > > > > Given that this one is in ip_fil_freebsd.c (specific to FreeBSD), it ca= n be > > removed. Others require more grokking. > > It can go. It was #if 0'd by ea3022cbbd3f5, IIRC in discussion with you a= t > the time (2013). > > ea3022cbbd3f5 converted timeout(9) to callout(9). This code remained as a= n > artifact of the conversion. It was sent by you to me following the ipfilt= er > upgrade from 4.1.28 to 5.1.2 earlier that year. > > > -- > Cheers, > Cy Schubert <Cy.Schubert@cschubert.com> > FreeBSD UNIX: <cy@FreeBSD.org> Web: https://FreeBSD.org > NTP: <cy@nwtime.org> Web: https://nwtime.org > > e^(i*pi)+1=3D0 > > > > > --=20 Jose Luis Duran
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