From nobody Wed Sep 01 17:49:07 2021 X-Original-To: freebsd-hackers@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 9F256178A723 for ; Wed, 1 Sep 2021 17:49:18 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: from mail-ua1-x929.google.com (mail-ua1-x929.google.com [IPv6:2607:f8b0:4864:20::929]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "smtp.gmail.com", Issuer "GTS CA 1O1" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4H0BQ63V67z4TWf for ; Wed, 1 Sep 2021 17:49:18 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: by mail-ua1-x929.google.com with SMTP id j31so294730uad.10 for ; Wed, 01 Sep 2021 10:49:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bsdimp-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=QFoKTSw3jziR9oVyF3vUR1c2l4H4WEVb6iIZMK/wIa4=; b=KWeY8pzusz7CV49XcsZ6ldXO4m2uHipjCp74UCUaD8RlLKvFS49fdXM9VDQbKqQrYQ +HSL/v7IJj46iKlFMWj+iXTXEneJ36KrT9lySrcazj0mZeijTj0YUcT07U3sxIcYA9rH //PFHihmt4NreZz7HwskfbmHVQ5c8rAhgO2W/u8n8T8H3JIo+69fRXcUrLwUWy6G4hU3 yj/lV5iHjnkeeldO9yJJVOP4+ryJL1aVVhU12DNp3emvh6hlGzvMl0z5S2D5YOGl4Kf3 nGDBOcn3enE24ad0PWCual56VJXNdgN6+tVwk/yfoLAnN7SsETOGlq8YfgvznpKJ04ma BREg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=QFoKTSw3jziR9oVyF3vUR1c2l4H4WEVb6iIZMK/wIa4=; b=hqC0iTj4SXf8VFtSntXYbnd7zeQSiH4hSwBLkf/poeJlR59dUET5JqNCAQSuMlWZ5A NdcaIuY+tNgAX7QeZyQ+rAw3ry1cB9e5zJINXN79VdttMTYmczujEMKMyt5NsNROcISE kPxCDqMmRGYlv+UNb89Qe+Yb5pmVMFF983uO0GSviuSohO3aGlOUReDU+m6vJJrDQhnr prYPrveQxNJlXNC7nxDOP7c78tbXAYb47e3cN3izKsAZt53/dlGIzlHWIq+86G7Mkmr/ Bg/dx7o+DsmHquD8mIUKntZKMKDJ/JNGk/ZQ03QAtZktk9U/fEuK8842GBBlXMsdqeYb 2mGQ== X-Gm-Message-State: AOAM530dpQMINfUIwimoXUyUw8FrqfIhdd+4Y+twAKMPeJ9Bvm4gu/6B 4kP8ek+K6rGVxqVP/6N95eSNDIIlTf5hhVc7HDhIIQ== X-Google-Smtp-Source: ABdhPJzgRF8INvuGnBw2ukGhmQzp0L18nRzyLzS5P2ZGEToMUoHPxceyPmZ8uY9NzGvr9TsHU2F1kDliqnWVGqpF3s4= X-Received: by 2002:a9f:31c8:: with SMTP id w8mr863992uad.77.1630518557953; Wed, 01 Sep 2021 10:49:17 -0700 (PDT) List-Id: Technical discussions relating to FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-hackers List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-hackers@freebsd.org MIME-Version: 1.0 References: <5476ea21-9e8a-32f5-08ff-add46c02d910@freebsd.org> <5d812d36e5291af35ecadf910a6d5f76b60f1441.camel@freebsd.org> In-Reply-To: <5d812d36e5291af35ecadf910a6d5f76b60f1441.camel@freebsd.org> From: Warner Losh Date: Wed, 1 Sep 2021 11:49:07 -0600 Message-ID: Subject: Re: Patched gpsd and /dev/pps0 results in "sleeping thread" kernel panic To: Ian Lepore Cc: Craig Leres , FreeBSD Hackers Content-Type: multipart/alternative; boundary="00000000000072604805caf2afba" X-Rspamd-Queue-Id: 4H0BQ63V67z4TWf X-Spamd-Bar: ---- Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[] X-ThisMailContainsUnwantedMimeParts: Y --00000000000072604805caf2afba Content-Type: text/plain; charset="UTF-8" On Wed, Sep 1, 2021 at 9:07 AM Ian Lepore wrote: > On Tue, 2021-08-31 at 22:35 -0600, Warner Losh wrote: > > On Tue, Aug 31, 2021 at 9:25 PM Warner Losh wrote: > > > > > > > > > > > On Tue, Aug 31, 2021 at 9:13 PM Ian Lepore wrote: > > > > > > > On Tue, 2021-08-31 at 21:07 -0600, Warner Losh wrote: > > > > > On Tue, Aug 31, 2021 at 8:11 PM Craig Leres > > > > > wrote: > > > > > > > > > > > > > > > > > On 8/31/21 6:54 PM, Warner Losh wrote: > > > > > > > Can you post a traceback? We recently tightened up the > > > > > > > sleeping > > > > > > conditions > > > > > > > and many of the panics are straight forward to fix > > > > > > > > > > > > Is this sufficient? > > > > > > > > > > > > > > > > Maybe. I'm guessing that the pps driver isn't setting > > > > > driver_mtx for > > > > > the > > > > > pps_state that it keeps, so when we're sleeping in pps_ioctl > > > > > we're > > > > > not > > > > > dropping the the ppbus lock, which leads to this diagnostic. > > > > > > > > > > Warner > > > > > > > > > > > > > > > > > > > > > > Exactly so, I've just been digging through the code. It's not an > > > > easy > > > > fix because the ppbus pps driver doesn't have access to the ppbus > > > > mutex > > > > at the point where it's registering to be a pps driver. > > > > > > > > > > I just came to the conclusion that either we'd need to create a > > > call in > > > ppbus > > > to set this mutex, or to return its lock... > > > > > > > > > > Craig, is there any chance you can configure your hardware so > > > > that the > > > > PPS signal is connected to either the CTS or DCD pin of a uart > > > > (even > > > > the same uart that's communicating with the gps receiver should > > > > work if > > > > you use DCD)? You'll get jitter and accuracy performance > > > > comparable to > > > > the parallel port pin, and avoid this mutex/sleeping problem. > > > > > > > > > > That's easier, but depending on the hardware might be harder :( > > > > > > > Either I'm missing something (likely am), or this might fix it up, > > or at least get away from the warning: > > > > https://reviews.freebsd.org/D31763 > > > > Note: I can't recall why ppbus has to be locked for this call. > > This code dates from the very earliest days of locking and > > so may do things simply because it seemed like a good idea > > without a specific notion as to what that lock is protecting. If > > so, the real fix may be to not take the lock in pps_ioctl at > > all and maybe instead use a reference count (the most > > often reason for 'a good idea' was to keep the device > > from going away, though this is a parent lock, not a > > child one so I'm less sure about that being the reason). > > > > Warner > > > > > > Yeah, figuring out whether it's safe to drop/re-aquire the ppsbus lock > at this point was the harder part of the work; I'm not very familiar > with the ppsbus stuff in general. > > Warner, I pointed out a small change needed to your proposed patch in > D31763. In the past I've found that one can't propose a different > patch in Phab without commandeering the entire change, so I just posted > an inline comment with the couple extra lines of code needed, hoping > you have more time today than I do to prepare a new patch. > I've updated the patch. Please review it and make sure I got it right. It was the same one that Craig came up with and tested as well. I'll commit if things are good and get into my MFC queue. Warner > -- Ian > > > > > Warner > > > > > > > > > > -- Ian > > > > > > > > > > > > > > > > > > Craig > > > > > > > > > > > > toc2 4 # kgdb /boot/kernel/kernel /var/crash/vmcore.1 > > > > > > GNU gdb (GDB) 10.2 [GDB v10.2 for FreeBSD] > > > > > > Copyright (C) 2021 Free Software Foundation, Inc. > > > > > > License GPLv3+: GNU GPL version 3 or later > > > > > > > > > > > > This is free software: you are free to change and > > > > > > redistribute it. > > > > > > There is NO WARRANTY, to the extent permitted by law. > > > > > > Type "show copying" and "show warranty" for details. > > > > > > This GDB was configured as "x86_64-portbld-freebsd12.2". > > > > > > Type "show configuration" for configuration details. > > > > > > For bug reporting instructions, please see: > > > > > > . > > > > > > Find the GDB manual and other documentation resources online > > > > > > at: > > > > > > . > > > > > > > > > > > > For help, type "help". > > > > > > Type "apropos word" to search for commands related to > > > > > > "word"... > > > > > > Reading symbols from /boot/kernel/kernel... > > > > > > Reading symbols from /boot/kernel.LBLNET/kernel.debug... > > > > > > > > > > > > Unread portion of the kernel message buffer: > > > > > > Sleeping thread (tid 101408, pid 2046) owns a non-sleepable > > > > > > lock > > > > > > KDB: stack backtrace of thread 101408: > > > > > > sched_switch() at sched_switch+0x630/frame 0xfffffe0070e4f760 > > > > > > mi_switch() at mi_switch+0xd4/frame 0xfffffe0070e4f790 > > > > > > sleepq_catch_signals() at sleepq_catch_signals+0x403/frame > > > > > > 0xfffffe0070e4f7e0 > > > > > > sleepq_timedwait_sig() at sleepq_timedwait_sig+0x14/frame > > > > > > 0xfffffe0070e4f820 > > > > > > _sleep() at _sleep+0x1b3/frame 0xfffffe0070e4f8a0 > > > > > > pps_ioctl() at pps_ioctl+0x298/frame 0xfffffe0070e4f8f0 > > > > > > ppsioctl() at ppsioctl+0x48/frame 0xfffffe0070e4f920 > > > > > > devfs_ioctl() at devfs_ioctl+0xb0/frame 0xfffffe0070e4f970 > > > > > > VOP_IOCTL_APV() at VOP_IOCTL_APV+0x7b/frame > > > > > > 0xfffffe0070e4f9a0 > > > > > > vn_ioctl() at vn_ioctl+0x16a/frame 0xfffffe0070e4fab0 > > > > > > devfs_ioctl_f() at devfs_ioctl_f+0x1e/frame > > > > > > 0xfffffe0070e4fad0 > > > > > > kern_ioctl() at kern_ioctl+0x2b7/frame 0xfffffe0070e4fb30 > > > > > > sys_ioctl() at sys_ioctl+0xfa/frame 0xfffffe0070e4fc00 > > > > > > amd64_syscall() at amd64_syscall+0x387/frame > > > > > > 0xfffffe0070e4fd30 > > > > > > fast_syscall_common() at fast_syscall_common+0xf8/frame > > > > > > 0xfffffe0070e4fd30 > > > > > > --- syscall (54, FreeBSD ELF64, sys_ioctl), rip = > > > > > > 0x8004c899a, rsp > > > > > > = > > > > > > 0x7fffdfdfc6a8, rbp = 0x7fffdfdfc730 --- > > > > > > panic: sleeping thread > > > > > > cpuid = 8 > > > > > > time = 1630456142 > > > > > > KDB: stack backtrace: > > > > > > db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame > > > > > > 0xfffffe005ab73ab0 > > > > > > vpanic() at vpanic+0x17b/frame 0xfffffe005ab73b00 > > > > > > panic() at panic+0x43/frame 0xfffffe005ab73b60 > > > > > > propagate_priority() at propagate_priority+0x282/frame > > > > > > 0xfffffe005ab73b90 > > > > > > turnstile_wait() at turnstile_wait+0x30c/frame > > > > > > 0xfffffe005ab73be0 > > > > > > __mtx_lock_sleep() at __mtx_lock_sleep+0x199/frame > > > > > > 0xfffffe005ab73c70 > > > > > > ppcintr() at ppcintr+0x2a0/frame 0xfffffe005ab73c90 > > > > > > ithread_loop() at ithread_loop+0x23c/frame 0xfffffe005ab73cf0 > > > > > > fork_exit() at fork_exit+0x7e/frame 0xfffffe005ab73d30 > > > > > > fork_trampoline() at fork_trampoline+0xe/frame > > > > > > 0xfffffe005ab73d30 > > > > > > --- trap 0, rip = 0, rsp = 0, rbp = 0 --- > > > > > > Uptime: 17m20s > > > > > > Dumping 607 out of 12240 > > > > > > MB:..3%..11%..22%..32%..43%..51%..61%..72%..82%..93% > > > > > > > > > > > > __curthread () at /usr/src/sys/amd64/include/pcpu_aux.h:55 > > > > > > 55 /usr/src/sys/amd64/include/pcpu_aux.h: No such file > > > > > > or > > > > > > directory. > > > > > > (kgdb) bt > > > > > > #0 __curthread () at > > > > > > /usr/src/sys/amd64/include/pcpu_aux.h:55 > > > > > > #1 doadump (textdump=1) at ../../../kern/kern_shutdown.c:371 > > > > > > #2 0xffffffff80b83ada in kern_reboot (howto=260) > > > > > > at ../../../kern/kern_shutdown.c:451 > > > > > > #3 0xffffffff80b83f33 in vpanic (fmt=, > > > > > > ap=) > > > > > > at ../../../kern/kern_shutdown.c:880 > > > > > > #4 0xffffffff80b83d53 in panic (fmt=) > > > > > > at ../../../kern/kern_shutdown.c:807 > > > > > > #5 0xffffffff80be7152 in propagate_priority > > > > > > (td=0xfffff80196959740) > > > > > > at ../../../kern/subr_turnstile.c:228 > > > > > > #6 0xffffffff80be7d1c in turnstile_wait > > > > > > (ts=0xfffff8000357a780, > > > > > > owner=, queue=0) at > > > > > > ../../../kern/subr_turnstile.c:785 > > > > > > #7 0xffffffff80b62ca9 in __mtx_lock_sleep > > > > > > (c=0xfffff80003969bd0, > > > > > > v=) at ../../../kern/kern_mutex.c:654 > > > > > > #8 0xffffffff8086fcc0 in ppcintr (arg=0xfffff80003969b00) > > > > > > at ../../../dev/ppc/ppc.c:1546 > > > > > > #9 0xffffffff80b4637c in intr_event_execute_handlers > > > > > > (p= > > > > > out>, > > > > > > ie=0xfffff800030d9d00) at ../../../kern/kern_intr.c:1143 > > > > > > #10 ithread_execute_handlers (p=, > > > > > > ie=0xfffff800030d9d00) > > > > > > at ../../../kern/kern_intr.c:1156 > > > > > > #11 ithread_loop (arg=0xfffff800039aa7e0) at > > > > > > ../../../kern/kern_intr.c:1236 > > > > > > #12 0xffffffff80b42e1e in fork_exit ( > > > > > > callout=0xffffffff80b46140 , > > > > > > arg=0xfffff800039aa7e0, > > > > > > frame=0xfffffe005ab73d40) at > > > > > > ../../../kern/kern_fork.c:1080 > > > > > > #13 > > > > > > (kgdb) > > > > > > > > > > > > > > > > > > > > > --00000000000072604805caf2afba--