Messages in this thread Patch in this message | | | Date | Tue, 3 Feb 2009 20:39:04 +0100 | From | Oleg Nesterov <> | Subject | [PATCH] ftrace: do_each_pid_task() needs rcu lock |
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"ftrace: use struct pid" commit 978f3a45d9499c7a447ca7615455cefb63d44165 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>
--- 6.29-rc3/kernel/trace/ftrace.c~FTRACE_PID 2009-01-12 23:07:51.000000000 +0100 +++ 6.29-rc3/kernel/trace/ftrace.c 2009-02-03 20:23:59.000000000 +0100 @@ -1736,9 +1736,12 @@ static void clear_ftrace_pid(struct 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); } @@ -1746,9 +1749,11 @@ static void set_ftrace_pid(struct pid *p { 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)
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