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[2003:e0:b73d:6f00:401d:1c7c:2fc2:2e2d]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5d806fedc68sm7774378a12.66.2024.12.25.06.07.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Dec 2024 06:07:03 -0800 (PST) In-Reply-To: <867c7n28sf.fsf@gnu.org> (Eli Zaretskii's message of "Wed, 25 Dec 2024 15:26:24 +0200") Received-SPF: pass client-ip=2a00:1450:4864:20::529; envelope-from=gerd.moellmann@gmail.com; helo=mail-ed1-x529.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:327094 Archived-At: Eli Zaretskii writes: >> From: Gerd M=C3=B6llmann >> Cc: pipcet@protonmail.com, ofv@wanadoo.es, emacs-devel@gnu.org, >> eller.helmut@gmail.com, acorallo@gnu.org >> Date: Wed, 25 Dec 2024 14:08:34 +0100 >>=20 >> Eli Zaretskii writes: >>=20 >> > So why are those unsafe? Because they access Lisp objects, or for >> > some other reason? >>=20 >> What do you mean with unsafe? We are accessing an object's memory. That >> memory may potentially be protected by a barrier. > > That's what I meant by "unsafe". I'm still wrapping my head around > this stuff, so apologies if I ask stupid questions.=20=20 No reason to apologize. We're just working on getting onto common ground, if that's an expression. > Here's another one: why accessing the same object's memory that may be > protected by a barrier OK from the main (a.k.a. "Lisp") thread, when > MPS could have meanwhile started GC asynchronously? IOW, how is this > "normal" access to Lisp objects different from access from a signal > handler? Under "normal" circumstances, in the main thread say, when we access an object that is behind a barrier, MPS gets invoked (signal, Mach exception), does its thing, removes the barrier, and lets the application continue. So the application doesn't notice anything. A problem occurs only, apparently (I've not read the MPS code), when the barrier handling code in MPS is called while being in another signal handler like Emacs' SIGPROF handler. I don't know what exactly the problem is in the end, in MPS. That would be a good question for Richard Brooksby, I think.