Date: Mon, 10 Apr 2023 09:33:08 -0500 From: "Jason A. Harmening" <jah@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 7b6fe2428a97 - main - DEBUG_VFS_LOCKS: use witness if available Message-ID: <ZDQeJGZtltkK3MgX@corona> In-Reply-To: <ZDOXYzk0hWzlnBVz@kib.kiev.ua> References: <202304092134.339LYYY5081080@gitrepo.freebsd.org> <ZDNU6whgpWktdeiw@corona> <ZDOXYzk0hWzlnBVz@kib.kiev.ua>
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On Mon, Apr 10, 2023 at 07:58:11AM +0300, Konstantin Belousov wrote: > On Sun, Apr 09, 2023 at 07:14:35PM -0500, Jason A. Harmening wrote: > > On Sun, Apr 09, 2023 at 09:34:34PM +0000, Konstantin Belousov wrote: > > > The branch main has been updated by kib: > > > > > > URL: https://cgit.FreeBSD.org/src/commit/?id=7b6fe2428a97921e8df882d0a24b87094c37b468 > > > > > > commit 7b6fe2428a97921e8df882d0a24b87094c37b468 > > > Author: Konstantin Belousov <kib@FreeBSD.org> > > > AuthorDate: 2023-04-08 06:15:00 +0000 > > > Commit: Konstantin Belousov <kib@FreeBSD.org> > > > CommitDate: 2023-04-09 21:34:12 +0000 > > > > > > DEBUG_VFS_LOCKS: use witness if available > > > > > > The assert_vop_locked messages are ignored, and file/line information > > > is not too useful. Fixing this without changing both witness and VFS > > > asserts KPIs is not possible. > > > > What was the motivation for this change? > I thought it was obvious, please look at the old assertion conditions, > now in the #else blocks. They are completely unable to handle shared > locks. In other words, if the current thread owns the lock shared, > or does not, ASSERT_VOP_UNLOCKED/ASSERT_VOP_LOCKED silently do nothing. Ah right, sorry. I keep forgetting we have a separate assert_vop_elocked() function for checking exclusive locks, while assert_vop_locked() just sort of gives up when it comes to shared locks. In any case, I like your proposal for restoring the diagnostics, thank you for posting it so quickly. > > > At first glance it seems regressive. I've at least found the assert > > messages, as well as the vnode state dumping done by vfs_badlock(), > > to be really useful for quick debugging of locking issues. This is > > especially true when optimization makes the backtrace and frame info > > less than useful; see commit 5a4a83fd0e67a0d7787d2f3e09ef0e5552a1ffb6 > > for a recent example. > This is fair, and I noted it in the commit message. But better working > asserts are IMO worth it. Eventually it might be fixed.
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