From nobody Mon Apr 04 23:03:14 2022 X-Original-To: dev-commits-src-main@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 9E3481A915D7; Mon, 4 Apr 2022 23:03:22 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4KXRCF5kcyz3GWg; Mon, 4 Apr 2022 23:03:21 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from tom.home (kib@localhost [127.0.0.1]) by kib.kiev.ua (8.16.1/8.16.1) with ESMTPS id 234N3Ewo023241 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Tue, 5 Apr 2022 02:03:17 +0300 (EEST) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua 234N3Ewo023241 Received: (from kostik@localhost) by tom.home (8.16.1/8.16.1/Submit) id 234N3EII023240; Tue, 5 Apr 2022 02:03:14 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Tue, 5 Apr 2022 02:03:14 +0300 From: Konstantin Belousov To: Mark Johnston Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 12fb39ec3e6b - main - proc: Relax proc_rwmem()'s assertion on the process hold count Message-ID: References: <202203011741.221Hftwu093303@gitrepo.freebsd.org> List-Id: Commit messages for the main branch of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-main List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-dev-commits-src-main@freebsd.org X-BeenThere: dev-commits-src-main@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FORGED_GMAIL_RCVD,FREEMAIL_FROM, NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.5 X-Spam-Checker-Version: SpamAssassin 3.4.5 (2021-03-20) on tom.home X-Rspamd-Queue-Id: 4KXRCF5kcyz3GWg X-Spamd-Bar: - Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=gmail.com (policy=none); spf=softfail (mx1.freebsd.org: 2001:470:d5e7:1::1 is neither permitted nor denied by domain of kostikbel@gmail.com) smtp.mailfrom=kostikbel@gmail.com X-Spamd-Result: default: False [-1.69 / 15.00]; RCVD_TLS_ALL(0.00)[]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-0.66)[-0.664]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; FREEMAIL_FROM(0.00)[gmail.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.10)[text/plain]; HAS_XAW(0.00)[]; NEURAL_HAM_LONG(-0.02)[-0.022]; TO_DN_SOME(0.00)[]; R_SPF_SOFTFAIL(0.00)[~all]; NEURAL_HAM_SHORT(-1.00)[-1.000]; MLMMJ_DEST(0.00)[dev-commits-src-all,dev-commits-src-main]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:6939, ipnet:2001:470::/32, country:US]; RCVD_COUNT_TWO(0.00)[2]; FREEMAIL_ENVFROM(0.00)[gmail.com]; DMARC_POLICY_SOFTFAIL(0.10)[gmail.com : No valid SPF, No valid DKIM,none] X-ThisMailContainsUnwantedMimeParts: N On Tue, Apr 05, 2022 at 02:01:04AM +0300, Konstantin Belousov wrote: > On Tue, Mar 01, 2022 at 05:41:55PM +0000, Mark Johnston wrote: > > The branch main has been updated by markj: > > > > URL: https://cgit.FreeBSD.org/src/commit/?id=12fb39ec3e6bc529feff3ba2862c6a4a30bd54eb > > > > commit 12fb39ec3e6bc529feff3ba2862c6a4a30bd54eb > > Author: Mark Johnston > > AuthorDate: 2022-03-01 16:48:39 +0000 > > Commit: Mark Johnston > > CommitDate: 2022-03-01 17:40:35 +0000 > > > > proc: Relax proc_rwmem()'s assertion on the process hold count > > > > This reference ensures that the process and its associated vmspace will > > not be destroyed while proc_rwmem() is executing. If, however, the > > calling thread belongs to the target process, then it is unnecessary to > > hold the process. In particular, fasttrap - a module which enables > > userspace dtrace - may frequently call proc_rwmem(), and we'd prefer to > > avoid the overhead of locking and bumping the hold count when possible. > In fact I am not sure it makes much sense to disable swap out for remote > process as well. With the current definition of p_hold, it only prevents > kstack pages reuse, which should be irrelevant for proc_rwmem(). What probably should be done is referencing the target process vmspace, instead. > > > > > Thus, make the assertion conditional on "p != curproc". Also assert > > that the process is not already exiting. No functional change intended. > > > > MFC after: 2 weeks > > Sponsored by: The FreeBSD Foundation > > --- > > sys/kern/sys_process.c | 9 +++++---- > > 1 file changed, 5 insertions(+), 4 deletions(-) > > > > diff --git a/sys/kern/sys_process.c b/sys/kern/sys_process.c > > index 582bff962f1a..8d8c5a1d34ff 100644 > > --- a/sys/kern/sys_process.c > > +++ b/sys/kern/sys_process.c > > @@ -336,11 +336,12 @@ proc_rwmem(struct proc *p, struct uio *uio) > > int error, fault_flags, page_offset, writing; > > > > /* > > - * Assert that someone has locked this vmspace. (Should be > > - * curthread but we can't assert that.) This keeps the process > > - * from exiting out from under us until this operation completes. > > + * Make sure that the process' vmspace remains live. > > */ > > - PROC_ASSERT_HELD(p); > > + if (p != curproc) > > + PROC_ASSERT_HELD(p); > > + KASSERT((p->p_flag & P_WEXIT) == 0, > > + ("%s: process %p is exiting", __func__, p)); > > PROC_LOCK_ASSERT(p, MA_NOTOWNED); > > > > /*