diff options
| author | Eric W. Biederman <ebiederm@xmission.com> | 2020-04-27 14:32:54 -0500 |
|---|---|---|
| committer | Eric W. Biederman <ebiederm@xmission.com> | 2020-04-28 16:42:03 -0500 |
| commit | 8feebc6713cd78cbba8c4e2a6d92299669052026 (patch) | |
| tree | ef0a0c158926256c3877092de317f00a0d2079be /kernel/time | |
| parent | 507122805edd25fcda8e959b870cd897b27a05c1 (diff) | |
| download | lwn-8feebc6713cd78cbba8c4e2a6d92299669052026.tar.gz lwn-8feebc6713cd78cbba8c4e2a6d92299669052026.zip | |
posix-cpu-timer: Tidy up group_leader logic in lookup_task
Replace has_group_leader_pid with thread_group_leader. Years ago Oleg
suggested changing thread_group_leader to has_group_leader_pid to handle
races. Looking at the code then and now I don't see how it ever helped.
Especially as then the code really did need to be the
thread_group_leader.
Today it doesn't make a difference if thread_group_leader races with
de_thread as the task returned from lookup_task in the non-thread case is
just used to find values in task->signal.
Since the races with de_thread have never been handled revert
has_group_header_pid to thread_group_leader for clarity.
Update the comment in lookup_task to remove implementation details that
are no longer true and to mention task->signal instead of task->sighand,
as the relevant cpu timer details are all in task->signal.
Ref: 55e8c8eb2c7b ("posix-cpu-timers: Store a reference to a pid not a task")
Ref: c0deae8c9587 ("posix-cpu-timers: Rcu_read_lock/unlock protect find_task_by_vpid call")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/posix-cpu-timers.c | 8 |
1 files changed, 2 insertions, 6 deletions
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 2fd3b3fa68bf..e4051e417bcb 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -69,12 +69,8 @@ static struct task_struct *lookup_task(const pid_t pid, bool thread, if (gettime) { /* * For clock_gettime(PROCESS) the task does not need to be - * the actual group leader. tsk->sighand gives + * the actual group leader. task->signal gives * access to the group's clock. - * - * Timers need the group leader because they take a - * reference on it and store the task pointer until the - * timer is destroyed. */ return (p == current || thread_group_leader(p)) ? p : NULL; } @@ -82,7 +78,7 @@ static struct task_struct *lookup_task(const pid_t pid, bool thread, /* * For processes require that p is group leader. */ - return has_group_leader_pid(p) ? p : NULL; + return thread_group_leader(p) ? p : NULL; } static struct task_struct *__get_task_for_clock(const clockid_t clock, |