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authorSergey Senozhatsky <sergey.senozhatsky@gmail.com>2016-01-01 23:03:01 +0900
committerIngo Molnar <mingo@kernel.org>2016-01-06 11:01:06 +0100
commit570f52412ae9432c56897472791ea8db420cbaf1 (patch)
treecc71138d056664627f7246a7a0f3dea3af283836
parent9e0e83a1eca66f8369e5a02973f85aad65c32416 (diff)
downloadleg-kernel-570f52412ae9432c56897472791ea8db420cbaf1.tar.gz
sched/core: Check tgid in is_global_init()
Our global init task can have sub-threads, so ->pid check is not reliable enough for is_global_init(), we need to check tgid instead. This has been spotted by Oleg and a fix was proposed by Richard a long time ago (see the link below). Oleg wrote: : Because is_global_init() is only true for the main thread of /sbin/init. : : Just look at oom_unkillable_task(). It tries to not kill init. But, say, : select_bad_process() can happily find a sub-thread of is_global_init() : and still kill it. I recently hit the problem in question; re-sending the patch (to the best of my knowledge it has never been submitted) with updated function comment. Credit goes to Oleg and Richard. Suggested-by: Richard Guy Briggs <rgb@redhat.com> Reported-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Eric W . Biederman <ebiederm@xmission.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Serge E . Hallyn <serge.hallyn@ubuntu.com> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://www.redhat.com/archives/linux-audit/2013-December/msg00086.html Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--include/linux/sched.h5
1 files changed, 3 insertions, 2 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index edad7a43edea..9cf9dd1c4cbe 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2002,7 +2002,8 @@ static inline int pid_alive(const struct task_struct *p)
}
/**
- * is_global_init - check if a task structure is init
+ * is_global_init - check if a task structure is init. Since init
+ * is free to have sub-threads we need to check tgid.
* @tsk: Task structure to be checked.
*
* Check if a task structure is the first user space task the kernel created.
@@ -2011,7 +2012,7 @@ static inline int pid_alive(const struct task_struct *p)
*/
static inline int is_global_init(struct task_struct *tsk)
{
- return tsk->pid == 1;
+ return task_tgid_nr(tsk) == 1;
}
extern struct pid *cad_pid;