Changes since v5: ================ - v5 can be seen here: https://lore.kernel.org/lkml/20250716123916.511889-1-bhupesh@xxxxxxxxxx/ - As suggested by Linus, replaced 'tsk->comm' with 'tsk->comm_str' locally, and verified basic thread names and then changed 'tsk->comm_str' back to 'tsk->comm'. So essentially now 'tsk->comm' is TASK_COMM_EXT_LEN i.e. 64-bytes long. Changes since v4: ================ - v4 can be seen here: https://lore.kernel.org/lkml/20250521062337.53262-1-bhupesh@xxxxxxxxxx/ - As suggested by Kees, replaced tsk->comm with tsk->comm_str, inside 'task_struct' where TASK_COMM_EXT_LEN is 64-bytes. Changes since v3: ================ - v3 can be seen here: https://lore.kernel.org/lkml/20250507110444.963779-1-bhupesh@xxxxxxxxxx/ - 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@xxxxxxxxxx/ - As suggested by Yafang and Kees, picked Linus' suggested approach for this version (see: <https://lore.kernel.org/all/CAHk-=wjAmmHUg6vho1KjzQi2=psR30+CogFd4aXrThr2gsiS4g@xxxxxxxxxxxxxx/>). - 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@xxxxxxxxxx/ - 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, Linus suggested 'tsk->comm' is made 64-byte long and equal to TASK_COMM_EXT_LEN. To avoid any surprises / bug,s I replaced 'tsk->comm' with 'tsk->comm_str' locally inside 'task_struct' and checked compilation of code and basic working of thread names: struct task_struct { .............. char comm_str[TASK_COMM_EXT_LEN]; .............. }; where TASK_COMM_EXT_LEN is 64-bytes. Once done, I changed the name back to 'tsk->comm'. To ensure that the existing ABI and userspace continues to work as intended, we ensure that: - Existing users of 'get_task_comm'/ 'set_task_comm' will get 'tsk->comm' truncated to a maximum of 'TASK_COMM_LEN' (16-bytes) to maintain ABI, - New / Modified users of 'get_task_comm'/ 'set_task_comm' will get 'tsk->comm' supported up to a maximum of 'TASK_COMM_EXT_LEN' (64-bytes). Note, that the existing users have not been modified to migrate to 'TASK_COMM_EXT_LEN', in case they have hard-coded expectations of dealing with only a 'TASK_COMM_LEN' long 'tsk->comm_str'. 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 include: Set tsk->comm length to 64 bytes include/linux/coredump.h | 3 ++- include/linux/sched.h | 15 +++++++++------ 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 ++ 7 files changed, 21 insertions(+), 7 deletions(-) -- 2.38.1
