ftrace: do_each_pid_task() needs rcu lock (229c4ef8) · Commits · e / devices / android_kernel_xiaomi_markw

"ftrace: use struct pid" commit converted ftrace_pid_trace to "struct pid*". But we can't use do_each_pid_task() without rcu_read_lock() even if we know the pid itself can't go away (it was pinned in ftrace_pid_write). The exiting task can detach itself from this pid at any moment. Signed-off-by:

Oleg Nesterov <oleg@redhat.com> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

kernel/trace/ftrace.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -1737,9 +1737,12 @@ static void clear_ftrace_pid(struct pid *pid)
		{
		struct task_struct *p;

		rcu_read_lock();
		do_each_pid_task(pid, PIDTYPE_PID, p) {
		clear_tsk_trace_trace(p);
		} while_each_pid_task(pid, PIDTYPE_PID, p);
		rcu_read_unlock();

		put_pid(pid);
		}

		@@ -1747,9 +1750,11 @@ static void set_ftrace_pid(struct pid *pid)
		{
		struct task_struct *p;

		rcu_read_lock();
		do_each_pid_task(pid, PIDTYPE_PID, p) {
		set_tsk_trace_trace(p);
		} while_each_pid_task(pid, PIDTYPE_PID, p);
		rcu_read_unlock();
		}

		static void clear_ftrace_pid_task(struct pid **pid)