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Fri, 15 May 2026 20:15:54 +0000 (UTC) Received: by fedora (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Fri, 15 May 2026 22:15:59 +0200 (CEST) Date: Fri, 15 May 2026 22:15:53 +0200 From: Oleg Nesterov To: Christian Brauner Cc: Minchan Kim , Jann Horn , Linus Torvalds , akpm@linux-foundation.org, hca@linux.ibm.com, linux-s390@vger.kernel.org, david@kernel.org, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, surenb@google.com, timmurray@google.com Subject: Re: [PATCH v3] mm: process_mrelease: introduce PROCESS_MRELEASE_REAP_KILL flag Message-ID: References: <20260511214226.937793-1-minchan@kernel.org> <20260515-nachdenken-umbenannt-a90006a46e14@brauner> MIME-Version: 1.0 In-Reply-To: <20260515-nachdenken-umbenannt-a90006a46e14@brauner> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-MFC-PROC-ID: p68G0LBdh4IeNDQMkw-4FmUmGAY3LARTGPJlkFubANg_1778876160 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Stat-Signature: 5o4w86fuyf3bb6phru3orwnetdnncps9 X-Rspam-User: X-Rspamd-Queue-Id: 6BF7212000C X-Rspamd-Server: rspam07 X-HE-Tag: 1778876166-5759 X-HE-Meta: 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 z1uoXcjb LVLzCuuISTiwf4QRMLuuhEroH4QZEVCOKFqed1IkXqOrl7bZrGwSuuUShkE1wo/ohKgSfivUuc9+7/oFxUlIZfqN6txiYo6XBeVKPqL+IgFETK4nLSXddaSFWT1XBwz6d55tR7rovgJ7LPxmcTEXfFbFjnJlzExdMWTqCKRS6ntxlhgPZ/MjtpZRE/RqzwHo0esnCuzkAU1qpLnr62yxg+8x5YzLcYHdUINUqwC+9aGLrodk2a0uxx8ZEzKPsJaA9yTAeFjFWrIgEaLJ8cvx/VxGthYUnLKOgpnheMa6EWDCSPQ6KJ+OZ2OxG9u8aVwDz9Sqz3nWXx1LVQyE1A0UWf95maOjyDFuyAgPqhUnkUdzNgPX8rHFKrUBTtwXqVQq2qI8CMK0Fglxou6TcD3j1+VK+P7Vapl8foJk8Hzrmye8y+8o= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: In fact I don't even understand the motivation... On 05/15, Christian Brauner wrote: > > On Mon, May 11, 2026 at 02:42:26PM -0700, Minchan Kim wrote: > > leaving the actual address space teardown (exit_mmap) to be deferred until > > the mm's reference count drops to zero. In the field (e.g., Android), > > arbitrary reference counts (reading /proc//cmdline, or various other > > remote VM accesses) frequently delay this teardown indefinitely, Sure, get_task_cmdline() can delay mmput(). But indefinitely ? Perhaps the changelog could be more clear? I don't see how any remote VM access can pin mm->mm_users "indefinitely". Even if, say, a lot of threads read /proc//cmdline in an endless loop in parallel... I must have missed something. Oleg.