Re: git: 1fa6daaafd74 - main - ipfilter: Avoid stopping with a lock held
Date: Tue, 12 Nov 2024 18:45:44 UTC
On Tue, Nov 12, 2024 at 3:41 PM Cy Schubert <Cy.Schubert@cschubert.com> wrote: > > I'm building a test patch on my sandbox machine. The patches in my git repo > will, > > a) remove another #if 0 from 2013, > b) revert this commit, > c) fix the "stopping with lock held" bug > > Testing on the sandbox is needed before I submit a review. > > You can revert this if you want, or I can push my three commits when my > testing is complete. I'll revert the commit, I feel better with this approach, thank you! > > > -- > 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=0 > > > In message <CAPwQLccpVdjUKQbCVQ0Vg5yRnmYSeKh+b+ThJwQY=z8OCZGOAw@mail.gmail.c > om> > , Jose Luis Duran writes: > > 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 > > -- Jose Luis Duran