"Dr. Thomas Orgis" <thomas.orgis@xxxxxxxxxxxxxx> writes: > Am Mon, 21 Feb 2022 09:49:12 +0100 > schrieb Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>: > >> As best as I can figure the intent is to return task->exit_code after >> a task exits. The field is returned with per task fields, so the >> exit_code of the entire process is not wanted. > > I wondered about the use of exit_code, too, when preparing my patch > that introduces ac_tgid and the AGROUP flag to identify the first and > last tasks of a task group/process, see > > https://lkml.org/lkml/2022/2/18/887 > > With the information about the position of this task in the group, > users can take some meaning from the exit code (individual kills?). The > old style ensured that you got one exit code per process. How do you figure? For single-threaded processes ac_exitcode would always be reasonable, and be what userspace passed to exit(3). For multi-threaded processes ac_exitcode before my change was set to some completely arbitrary value for the thread whose tgid == tid. Frequently the thread whose tgid == tid is the last thread to exit and is brought down by a call to group_exit so it makes sense. Unfortunately there is no requirement for that to be the case. If the thread whose tgid == tid happens to call pthread_exit the value in ac_exitcode for that thread is pretty much undefined. The ac_exitcode for the other threads would be the useless value of 0 that the field was initialized to. With my change the value returned is at least well defined. But thread_group_leader in this context does nothing except limit the value that is returned. > I addressing ac_exitcode fits together with my patch, while increasing > the version of taskstats helps clients that then can know that > ac_exitcode now has a different meaning. Right now this is a change > under the hood and you can just guess (or have to know from the kernel > version). As best as I can tell I did not change the meaning of the field. I change buggy code, and removed an arbitrary and senseless filter. Now maybe it would have been better to flag the bug fix with a version number. Unfortunately I did not even realize taskstats had a version number. I just know the code made no sense. Eric
