[PATCH] proc: drop tasklist lock in task_state() (b0fa9db6) · Commits · 戴 / test

task_state() needs tasklist_lock to protect ->parent/->real_parent. However task->parent points to nowhere only when the actions below happen in order 1) release_task(task) 2) release_task(task->parent) 3) a grace period passed But 3) implies that the memory ops from 1) should be finished, so pid_alive() can't be true in such a case. Otherwise, we don't care if ->parent/->real_parent changes under us. Signed-off-by:

Oleg Nesterov <oleg@tv-sign.ru> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by:

Andrew Morton <akpm@osdl.org> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

fs/proc/array.c

+5 −6

Original line number	Diff line number	Diff line
		@@ -162,7 +162,7 @@ static inline char * task_state(struct task_struct p, char buffer)
		int g;
		struct fdtable *fdt = NULL;

		read_lock(&tasklist_lock);
		rcu_read_lock();
		buffer += sprintf(buffer,
		"State:\t%s\n"
		"SleepAVG:\t%lu%%\n"
		@@ -174,14 +174,13 @@ static inline char * task_state(struct task_struct p, char buffer)
		"Gid:\t%d\t%d\t%d\t%d\n",
		get_task_state(p),
		(p->sleep_avg/1024)*100/(1020000000/1024),
		p->tgid,
		p->pid, pid_alive(p) ? p->group_leader->real_parent->tgid : 0,
		pid_alive(p) && p->ptrace ? p->parent->pid : 0,
		p->tgid, p->pid,
		pid_alive(p) ? rcu_dereference(p->real_parent)->tgid : 0,
		pid_alive(p) && p->ptrace ? rcu_dereference(p->parent)->pid : 0,
		p->uid, p->euid, p->suid, p->fsuid,
		p->gid, p->egid, p->sgid, p->fsgid);
		read_unlock(&tasklist_lock);

		task_lock(p);
		rcu_read_lock();
		if (p->files)
		fdt = files_fdtable(p->files);
		buffer += sprintf(buffer,

Admin message