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Thu, 26 Feb 2026 07:46:35 -0500 X-MC-Unique: KHvnGr7SPuCRykxddpXmIg-1 X-Mimecast-MFC-AGG-ID: KHvnGr7SPuCRykxddpXmIg_1772109992 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D73DF19560A3; Thu, 26 Feb 2026 12:46:31 +0000 (UTC) Received: from fedora (unknown [10.44.32.38]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 5E75419560B8; Thu, 26 Feb 2026 12:46:25 +0000 (UTC) Received: by fedora (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 26 Feb 2026 13:46:31 +0100 (CET) Date: Thu, 26 Feb 2026 13:46:23 +0100 From: Oleg Nesterov To: Andrei Vagin Cc: Pavel Tikhomirov , Christian Brauner , Shuah Khan , Kees Cook , Andrew Morton , David Hildenbrand , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Jan Kara , Aleksa Sarai , Andrei Vagin , Kirill Tkhai , Alexander Mikhalitsyn , Adrian Reber , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v3 2/4] pid: check init is created first after idr alloc Message-ID: References: <20260224164852.306583-1-ptikhomirov@virtuozzo.com> <20260224164852.306583-3-ptikhomirov@virtuozzo.com> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Mimecast-MFC-PROC-ID: OXAkNuHGL0dE4ZEsc2x_MF5ysoF6T3azb8LBCjflLIQ_1772109992 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspamd-Server: rspam09 X-Stat-Signature: 7ujsg4z9cgji8uyeb6u19nek4mmdjcaf X-Rspamd-Queue-Id: 1ACCB14000E X-Rspam-User: X-HE-Tag: 1772109999-932505 X-HE-Meta: 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 JVHzIaPB 5o3QOPCJmFx8Ch1FAN+IN+HF9VaSTNDKEMBIDXeDUQEJOt5Sr2b3P69PRmyaM9QC9REKVx4NPAgCW1aPcOMpOCtYVlDcJJZnG8DUDUnfSXvYp8SQtldAteTQBZT+MxLZWm3aPFRMrS8W08dcvXVm/jbb/f4LHHaGINNUUpmCFEgffq3rwWiXBB4UsS62/EhNoBaEGwOZYHJbEnRT9af7eG5hzM6K/3i2yFn147RsS466A+bbc+NJD1iy3L/s7fsrgEVJ/vxgIUmVUPvGctc+TZ6GJQSZzrSGj7wYnbxo0q9Gj5HubDuvdiIJ2zpfGxf1Y4pXljOE62NmZhcjfF/zIRw+uum2AINbH/VGn Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 02/25, Oleg Nesterov wrote: > > On 02/24, Andrei Vagin wrote: > > > > This isn't directly related to this patch, but why do we check > > "ns->pid_allocated & PIDNS_ADDING" after allocating all pids? Wouldn't > > it be more reasonable to do that right after taking the pidmap_lock? > > Perhaps, but alloc_pid() can drop pidmap_lock and retry, so we will > need to re-check PIDNS_ADDING. Now that I look at this code again... Why do we bother to check "pid_allocated & PIDNS_ADDING" at all? copy_process() does /* Don't start children in a dying pid namespace */ if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) { retval = -ENOMEM; goto bad_fork_core_free; } I am going to send the patch which removes this check from alloc_pid... Need to recheck. Oleg.