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[46.135.95.94]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ab703fbcc0csm932221866b.53.2025.02.05.12.09.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Feb 2025 12:09:38 -0800 (PST) From: Mateusz Guzik To: ebiederm@xmission.com, oleg@redhat.com Cc: brauner@kernel.org, akpm@linux-foundation.org, Liam.Howlett@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mateusz Guzik Subject: [PATCH v5 1/5] exit: perform add_device_randomness() without tasklist_lock Date: Wed, 5 Feb 2025 21:09:25 +0100 Message-ID: <20250205200929.406568-2-mjguzik@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250205200929.406568-1-mjguzik@gmail.com> References: <20250205200929.406568-1-mjguzik@gmail.com> MIME-Version: 1.0 X-Stat-Signature: 7dc98uok1ifhxb7xbxreyyiw9r7jdd9h X-Rspam-User: X-Rspamd-Queue-Id: 23D5C1A000F X-Rspamd-Server: rspam03 X-HE-Tag: 1738786180-932627 X-HE-Meta: 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 9skNkDKs wKPaZeey4MBLy+wSwpfYopm5w6x14Zdl8//okBrtPJD4wRnn3ZrHimRpNi6AmSs7RRStMsAR5ZKrXbiD/iEhIyRl/xtRWLjelANdFnq8eJJKXIKydtmoafEPpzHydUEEszHlntFf69pv271Hqrp8+sz2koIW+3UR993+JXTa/Ela8GrQr6cCwGD1xtzdLJye6uLouUJjAizqGbt7GkRFf9F5U6xLvR++m9ZmH+j/1LNcL2I2ZdQEiJzKglln1ohZ5ngrL4TSeWKUGSgYd869TY2wLKs5LC21Zi7OUcy+9KgxuTwmTpMe8H6P+eZFHK1S6pUIQN1cU3dK/h8DwoQRpRpwoob/kRc7LDRK5UQBNTWwgb2bU3zseZOWxzs93Zox8eO7wYONzrOUHwE/hCwOyodS/Gh+6iRGof4jbnCQYQyEtSkf4sroJPK1Ji6Sb8BnhtMUX X-Bogosity: Ham, tests=bogofilter, spamicity=0.000241, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Parallel calls to add_device_randomness() contend on their own. The clone side aleady runs outside of tasklist_lock, which in turn means any caller on the exit side extends the tasklist_lock hold time while contending on the random-private lock. Reviewed-by: Oleg Nesterov Signed-off-by: Mateusz Guzik --- kernel/exit.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index 3485e5fc499e..c79b41509cd3 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -174,9 +174,6 @@ static void __exit_signal(struct task_struct *tsk) sig->curr_target = next_thread(tsk); } - add_device_randomness((const void*) &tsk->se.sum_exec_runtime, - sizeof(unsigned long long)); - /* * Accumulate here the counters for all threads as they die. We could * skip the group leader because it is the last user of signal_struct, @@ -278,6 +275,9 @@ void release_task(struct task_struct *p) write_unlock_irq(&tasklist_lock); proc_flush_pid(thread_pid); put_pid(thread_pid); + add_device_randomness(&p->se.sum_exec_runtime, + sizeof(p->se.sum_exec_runtime)); + free_pids(post.pids); release_thread(p); put_task_struct_rcu_user(p);