From owner-svn-src-head@freebsd.org Sat Feb 17 18:47:40 2018 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id D668CF0328E; Sat, 17 Feb 2018 18:47:39 +0000 (UTC) (envelope-from mjguzik@gmail.com) Received: from mail-qk0-x243.google.com (mail-qk0-x243.google.com [IPv6:2607:f8b0:400d:c09::243]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 5D3DC8E224; Sat, 17 Feb 2018 18:47:39 +0000 (UTC) (envelope-from mjguzik@gmail.com) Received: by mail-qk0-x243.google.com with SMTP id b130so7773118qkg.9; Sat, 17 Feb 2018 10:47:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=JUTgfSFBxZ22joGIJLhtM1DR+t8nO6AzUB8hG3fSLSw=; b=qgNrBciXZhIKPXSAzJU/3wiBIoaYo4E6AkIw7YZ20jUftvKALPgPOQ+Vo+8nmoUJaG PxbjORJe2y0HO/AzkqyphfPebVyUa7CqI6MLKePzRjvFMoNB07j6GI16G3lW12fus7zq 77cv5OTrnQ9HSWy8t1jHyWQQqA9/mHKtGtgtxHhVn234mskE+6ZIeXMpynV8toqLCTbZ EjJAV9h6oPaOfpQSvKmpAw890S/oC1oqVhLTVXHbogI0e1YnlmyY+m3ofS+WiVh1e9Bx YCWN6h59QrKop42u/F7PmIn74l5Pitr1ecGyWoCgFBIru8G4RiwZ4jFkeMXCkH5ltMYq Hrtg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=JUTgfSFBxZ22joGIJLhtM1DR+t8nO6AzUB8hG3fSLSw=; b=LTKhteCocqE6NkrlzrvbrPM78hR0w6Fn4dUtfExYSzUJKb5ZFSoe0tDxxBwNlU+gyy FK8Ufuo+6wNUwzc5kb54q+b00c9myXFdFgZcEXDrjqSfAwoLPVNpXP7Op/+SRZZJuFZ6 prf7grQF3hEwTFYoZLAuLhvb00p6ZCm4wUsWsiOgQvNmbT6lSqozvFKQWaK3+eLQ9j2s b8oyesq7LkEK2368wr+L0zi7ZADZHuoKMx6uL5iA1kxyiFIq4o+r7kJX5AUFSaVB2Ehw 7yjMRo3JzILlCHTKZebM43ESESvE9Dh2M0w6HF4JFRxlrZ6sExjCBxqVNZ9N70+E0KQ8 UPxg== X-Gm-Message-State: APf1xPB4qXtC77TGnxR5C8ZjsjWaC+HByJ5BSj6RzwbmCt59tXO1KsGN g/l8IwY+X+AoABiGJJAOfA9RkG11y1cgpYJaq1U= X-Google-Smtp-Source: AH8x226pvr68V3cZBUH367gqFRoQ34ChnTaUxkkMjY+NdrU4OtMehlXy0i7ZLRovu8JwU+cCyV2+FKLjdGzOTV3lVHQ= X-Received: by 10.55.74.2 with SMTP id x2mr15449076qka.314.1518893259033; Sat, 17 Feb 2018 10:47:39 -0800 (PST) MIME-Version: 1.0 Received: by 10.237.58.99 with HTTP; Sat, 17 Feb 2018 10:47:38 -0800 (PST) In-Reply-To: <20180217184259.GA84054@x2.osted.lan> References: <201802170848.w1H8mkfb081764@repo.freebsd.org> <20180217112738.GO94212@kib.kiev.ua> <20180217162632.GQ94212@kib.kiev.ua> <20180217163822.GA81555@x2.osted.lan> <20180217184259.GA84054@x2.osted.lan> From: Mateusz Guzik Date: Sat, 17 Feb 2018 19:47:38 +0100 Message-ID: Subject: Re: svn commit: r329448 - head/sys/kern To: Peter Holm Cc: Konstantin Belousov , Mateusz Guzik , src-committers , svn-src-all@freebsd.org, svn-src-head@freebsd.org Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.25 X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 17 Feb 2018 18:47:40 -0000 On Sat, Feb 17, 2018 at 7:42 PM, Peter Holm wrote: > On Sat, Feb 17, 2018 at 06:34:34PM +0100, Mateusz Guzik wrote: > > On Sat, Feb 17, 2018 at 5:38 PM, Peter Holm wrote: > > > > > On Sat, Feb 17, 2018 at 06:26:32PM +0200, Konstantin Belousov wrote: > > > > On Sat, Feb 17, 2018 at 05:07:07PM +0100, Mateusz Guzik wrote: > > > > > On Sat, Feb 17, 2018 at 01:27:38PM +0200, Konstantin Belousov > wrote: > > > > > > On Sat, Feb 17, 2018 at 08:48:46AM +0000, Mateusz Guzik wrote: > > > > > > > Author: mjg > > > > > > > Date: Sat Feb 17 08:48:45 2018 > > > > > > > New Revision: 329448 > > > > > > > URL: https://svnweb.freebsd.org/changeset/base/329448 > > > > > > > > > > > > > > Log: > > > > > > > exit: get rid of PROC_SLOCK when checking a process to report > > > > > > Was this tested ? > > > > > > > > > > > > > > > > I was trussing multithreaded microbenchmarks, no issues. > > > > > > > > > > > In particular, are you aware of r309539 ? > > > > > > > > > > > > > > > > So it looks like I misread the code - I have grepped > > > > > thread_suspend_switch operating with the proc locked and misread > > > > > thread_suspend_one's assert as PROC_LOCK_ASSERT. > > > > > > > > > > That said, I think this is harmless. Regardless of the lock the > > > > > inspecting thread can race and check "too soon". Even for a case > where > > > > > it decides to report, I don't see anything which would depend on > the > > > > > suspending thread to finish. > > > > It was definitely not harmless when I tried to avoid the spin lock > there, > > > > but I do not remember exact failure mode. Most likely, it was a > missed > > > > report of the traced child indeed, but I am not sure that truss > triggered > > > > it. Most likely, Peter Holm was the reporter, since he is listed in > > > > the commit. > > > > > > > > > > I ran a truss(1) test on r329456 and it fails. I have not had a > > > chance to look closer at this, but this is what I see: > > > > > > [root@mercat1 /home/pho]# pgrep truss | xargs ps -Hlp > > > UID PID PPID CPU PRI NI VSZ RSS MWCHAN STAT TT TIME COMMAND > > > 0 41149 41118 0 52 0 11532 2588 wait I 0 0:01.38 truss > > > /tmp/ttruss 10 > > > 0 41151 41149 0 52 0 13156 2300 - TX 0 0:00.98 > /tmp/ttruss > > > 10 > > > 0 41151 41149 0 52 0 13156 2300 - TX 0 0:00.00 > /tmp/ttruss > > > 10 > > > [root@mercat1 /home/pho]# procstat -k 41151 > > > PID TID COMM TDNAME KSTACK > > > 41151 100211 ttruss - mi_switch > > > thread_suspend_switch ptracestop amd64_syscall fast_syscall_common > > > 41151 100765 ttruss - mi_switch > > > thread_suspend_check ast doreti_ast > > > [root@mercat1 /home/pho]# > > > > > > > > Ok, I reproduced the bug with your script. I reverted the change. > > > > The patch I mailed in this thread fixes it for me. Below is a variant > > which can be applied on top of fresh head: > > > > https://people.freebsd.org/~mjg/wait6_slock.diff > > > > Yes, this also works for me with the truss(1) test scenario. > Would you like me to run the full set of test? > > If you have free cycles I don't see why not, thanks. -- Mateusz Guzik