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change next_thread() to use __next_thread() ?: group_leader

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This relies on fact that group leader is always the 1st entry in the
signal->thread_head list.

With or without this change, if the lockless next_thread(last_thread)
races with exec it can return the old or the new leader.

We are almost ready to kill task->thread_group, after this change its
only user is thread_group_empty().

Link: https://lkml.kernel.org/r/20230824143201.GB31222@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2023-08-24 16:32:01 +02:00 committed by Andrew Morton
parent 33a9813825
commit d639cf4abb
1 changed files with 2 additions and 3 deletions
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5
include/linux/sched/signal.h
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@ -726,10 +726,9 @@ static inline struct task_struct *__next_thread(struct task_struct *p)
thread_node);
}
static inline struct task_struct *next_thread(const struct task_struct *p)
static inline struct task_struct *next_thread(struct task_struct *p)
{
return list_entry_rcu(p->thread_group.next,
struct task_struct, thread_group);
return __next_thread(p) ?: p->group_leader;
}
static inline int thread_group_empty(struct task_struct *p)