From: Yiyang Chen Date: Sun, 29 Mar 2026 19:00:40 +0000 (+0800) Subject: taskstats: set version in TGID exit notifications X-Git-Url: http://git.ipfire.org/index.cgi?a=commitdiff_plain;h=16c4f0211aaa1ec1422b11b59f64f1abe9009fc0;p=thirdparty%2Fkernel%2Flinux.git taskstats: set version in TGID exit notifications delay accounting started populating taskstats records with a valid version field via fill_pid() and fill_tgid(). Later, commit ad4ecbcba728 ("[PATCH] delay accounting taskstats interface send tgid once") changed the TGID exit path to send the cached signal->stats aggregate directly instead of building the outgoing record through fill_tgid(). Unlike fill_tgid(), fill_tgid_exit() only accumulates accounting data and never initializes stats->version. As a result, TGID exit notifications can reach userspace with version == 0 even though PID exit notifications and TASKSTATS_CMD_GET replies carry a valid taskstats version. This is easy to reproduce with `tools/accounting/getdelays.c`. I have a small follow-up patch for that tool which: 1. increases the receive buffer/message size so the pid+tgid combined exit notification is not dropped/truncated 2. prints `stats->version`. With that patch, the reproducer is: Terminal 1: ./getdelays -d -v -l -m 0 Terminal 2: taskset -c 0 python3 -c 'import threading,time; t=threading.Thread(target=time.sleep,args=(0.1,)); t.start(); t.join()' That produces both PID and TGID exit notifications for the same process. The PID exit record reports a valid taskstats version, while the TGID exit record reports `version 0`. This patch (of 2): Set stats->version = TASKSTATS_VERSION after copying the cached TGID aggregate into the outgoing netlink payload so all taskstats records are self-describing again. Link: https://lkml.kernel.org/r/ba83d934e59edd431b693607de573eb9ca059309.1774810498.git.cyyzero16@gmail.com Fixes: ad4ecbcba728 ("[PATCH] delay accounting taskstats interface send tgid once") Signed-off-by: Yiyang Chen Cc: Balbir Singh Cc: Dr. Thomas Orgis Cc: Fan Yu Cc: Wang Yaxin Cc: Signed-off-by: Andrew Morton --- diff --git a/kernel/taskstats.c b/kernel/taskstats.c index 0cd680ccc7e53..73bd6a6a78935 100644 --- a/kernel/taskstats.c +++ b/kernel/taskstats.c @@ -649,6 +649,7 @@ void taskstats_exit(struct task_struct *tsk, int group_dead) goto err; memcpy(stats, tsk->signal->stats, sizeof(*stats)); + stats->version = TASKSTATS_VERSION; send: send_cpu_listeners(rep_skb, listeners);