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bh=Gy0LHTdLmlPA2i+iN2Je30fdWIJBmw4l6fKDIDT15Cc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=cdY4lVPEYrNPl4E1WB89Pyctf4ei4UjwuF0x5VaUZ/uHD8RP//KUfcDlDlXD/ZTMz 4jsOCEDRAult1wHuB6kgB9dPNw4l/aXf3iKX5DOr7uzAVhOh5XiMoI801LGS3cOdFY iYUnfiVA+rR0pNdM9dXCMb8naE0yjNA7UicT2d5I= Date: Mon, 15 Jun 2026 12:15:58 +0100 From: Catalin Marinas To: Breno Leitao Cc: Andrew Morton , lance.yang@linux.dev, Davidlohr Bueso , Oleg Nesterov , Qian Cai , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, stable@vger.kernel.org Subject: Re: [PATCH v2] mm/kmemleak: avoid soft lockup when scanning task stacks Message-ID: References: <20260612-kmemleak-stack-resched-v2-1-53240de79e88@debian.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 3183E140003 X-Stat-Signature: yhxxhfw5etnt8kg8ifebb1ab8cw8yqw5 X-HE-Tag: 1781522165-151713 X-HE-Meta: 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 GIsu6sio rdrhyvEAzpYbZwyJVksZNLfyQGoeafPLr4iXtwsjez0zQbZllSZvCVEU2RNdyo2gDC4rgkTafl/WpMtmjcSnQRpEgHppsbY9EGIvR6Bou6TOFigF140KHLq5gdueA7g6xMtsAjOqITcN+B4FqEhuTN9LANaVbJ4q7bQOA104CN0VSn7t+nf8vUL6aZhOM03047HsfURIGk5Q0QeXp5yVU7XyTme06djnWp4zDmrOILFACms8= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Breno, On Mon, Jun 15, 2026 at 02:27:13AM -0700, Breno Leitao wrote: > On Fri, Jun 12, 2026 at 06:11:40PM +0100, Catalin Marinas wrote: > > if (kmemleak_stack_scan) { > > struct pid *pid; > > int nr = 1; > > > > do { > > struct task_struct *p = NULL; > > > > rcu_read_lock(); > > pid = find_ge_pid(nr, &init_pid_ns); > > if (pid) { > > nr = pid_nr(pid) + 1; > > p = pid_task(pid, PIDTYPE_PID); > > if (p) > > get_task_struct(p); > > } > > rcu_read_unlock(); > > > > if (p) { > > void *stack = try_get_task_stack(p); > > > > if (stack) { > > scan_block(stack, stack + THREAD_SIZE, > > NULL); > > put_task_stack(p); > > } > > put_task_struct(p); > > } > > Should we add a scan_should_stop() check here to allow early > termination? Ah, yes, I think we should, maybe as 'while (pid && !scan_should_stop())'. scan_block() already bails out early but it will still go quickly through all the stacks which we don't need. As a later clean-up, I wonder whether we should change scan_block() to return non-zero and use that. -- Catalin