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Received: from [223.233.70.209] (helo=localhost.localdomain) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1uHcrm-00B3oN-8q; Wed, 21 May 2025 08:23:50 +0200 From: Bhupesh To: akpm@linux-foundation.org Cc: bhupesh@igalia.com, kernel-dev@igalia.com, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, oliver.sang@intel.com, lkp@intel.com, laoar.shao@gmail.com, pmladek@suse.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, arnaldo.melo@gmail.com, alexei.starovoitov@gmail.com, andrii.nakryiko@gmail.com, mirq-linux@rere.qmqm.pl, peterz@infradead.org, willy@infradead.org, david@redhat.com, viro@zeniv.linux.org.uk, keescook@chromium.org, ebiederm@xmission.com, brauner@kernel.org, jack@suse.cz, mingo@redhat.com, juri.lelli@redhat.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-trace-kernel@vger.kernel.org Subject: [PATCH v4 0/3] Add support for long task name Date: Wed, 21 May 2025 11:53:34 +0530 Message-Id: <20250521062337.53262-1-bhupesh@igalia.com> X-Mailer: git-send-email 2.38.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: ox3ix5jgt1mhi98mo1gxcou4nx9rcxkp X-Rspam-User: X-Rspamd-Queue-Id: B456740005 X-Rspamd-Server: rspam06 X-HE-Tag: 1747808642-265910 X-HE-Meta: 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 dl5VEPWI KVZxDvKjJt/IEtUCLK0VbMbFMSre8twL0f/MUIjRkmYxzocRIz6pnXorNzt/vH8sWz90E17jL86MKZszKLYg1ces0UbVojjbZ94Rn2QO7IAu1ox/8mlyWOvlPrdNbgJ0ZXlAga6KM//zTRGP38s+pvtEY03DbdWsRSQ1n8DE9bfCjO5XEDfea0jtxy5g3W/vX6KbGMapCJoYB7KtglL+VARDqFoUIkh8QEAqqett0uRhHDkMhV6JFzKs0mAkSBBTZUsYO1Nai8WGp8AGSOOO/408juojM1WvFU8FGALJ+XgHpBp8/LnJMZ1VbAiMJZAdDKo3ydA0cq1H/KNZsuBxjYaUJOx2GWnDujXzWA57q6FQ1wTp4HiX+at8EtaSpjbSK0tcA49F8w6bjITMsZzk4NrHFv0LkN6rzcUJr X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Changes since v3: ================ - v3 can be seen here: https://lore.kernel.org/lkml/20250507110444.963779-1-bhupesh@igalia.com/ - As suggested by Petr and Steven, used 'comm_ext' name instead of 'real_comm'. Correspondingly the macro name is changed to 'TASK_COMM_EXT_LEN' for the 64-byte extended comm. - Rebased this patchset on linux-next/master, which contain the following patch from Steven now: 155fd6c3e2f0 ("tracing/sched: Use __string() instead of fixed lengths for task->comm") - Accordingly, v4 drops the changes done for 'trace/sched' events in v3, but retains the 'safe' memcpy' changes for other kernel trace users. Changes since v2: ================ - v2 can be seen here: https://lore.kernel.org/lkml/20250331121820.455916-1-bhupesh@igalia.com/ - As suggested by Yafang and Kees, picked Linus' suggested approach for this version (see: ). - Dropped kthreads patch from this version. It would be sent out separately, if we have a consensus on this approach. Changes since v1: ================ - v1 can be seen here: https://lore.kernel.org/lkml/20250314052715.610377-1-bhupesh@igalia.com/ - As suggested by Kees, added [PATCH 3/3] to have a consistent 'full_name' entry inside 'task_struct' which both tasks and kthreads can use. - Fixed the commit message to indicate that the existing ABI '/proc/$pid/task/$tid/comm' remains untouched and a parallel '/proc/$pid/task/$tid/full_name' ABI for new (interested) users. While working with user-space debugging tools which work especially on linux gaming platforms, I found that the task name is truncated due to the limitation of TASK_COMM_LEN. Now, during debug tracing, seeing truncated names is not very useful, especially on gaming platforms where the number of tasks running can be very high. This patchset does not touch 'TASK_COMM_LEN' at all, i.e. 'TASK_COMM_LEN' and the 16-byte design remains untouched. Via this patchset, as Linus suggested, we can add the following union inside 'task_struct': union { char comm[TASK_COMM_LEN]; char comm_ext[TASK_COMM_EXT_LEN]; }; and then modify '__set_task_comm()' to pass 'tsk->comm_ext' to the existing users. So, eventually: - users who want the existing 'TASK_COMM_LEN' behavior will get it (existing ABIs would continue to work), - users who just print out 'tsk->comm' as a string will get the longer new "extended comm", - users who do 'sizeof(->comm)' will continue to get the old value because of the union. After this change, gdb is able to show full name of the task, using a simple app which generates threads with long names [see 1]: # gdb ./threadnames -ex "run info thread" -ex "detach" -ex "quit" > log # cat log NameThatIsTooLongForComm[4662] [1]. https://github.com/lostgoat/tasknames Bhupesh (3): exec: Remove obsolete comments treewide: Switch memcpy() users of 'task->comm' to a more safer implementation exec: Add support for 64 byte 'tsk->comm_ext' fs/exec.c | 6 +++--- include/linux/coredump.h | 3 ++- include/linux/sched.h | 14 ++++++++------ include/trace/events/block.h | 5 +++++ include/trace/events/oom.h | 1 + include/trace/events/osnoise.h | 1 + include/trace/events/signal.h | 1 + include/trace/events/task.h | 2 ++ 8 files changed, 23 insertions(+), 10 deletions(-) -- 2.38.1