Commit ea73c79e authored Apr 13, 2014 by Oleg Nesterov Committed by Steven Rostedt Jun 21, 2014

tracing: syscall_regfunc() should not skip kernel threads

syscall_regfunc() ignores the kernel threads because "it has no effect",
see cc3b13c1 "Don't trace kernel thread syscalls" which added this check.

However, this means that a user-space task spawned by call_usermodehelper()
will run without TIF_SYSCALL_TRACEPOINT if sys_tracepoint_refcount != 0.

Remove this check. The unnecessary report from ret_from_fork path mentioned
by cc3b13c1 is no longer possible, see See commit fb45550d "make sure
that kernel_thread() callbacks call do_exit() themselves".

A kernel_thread() callback can only return and take the int_ret_from_sys_call
path after do_execve() succeeds, otherwise the kernel will crash. But in this
case it is no longer a kernel thread and thus is needs TIF_SYSCALL_TRACEPOINT.

Link: http://lkml.kernel.org/p/20140413185938.GD20668@redhat.com

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

parent 8063e41d

kernel/tracepoint.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -497,8 +497,6 @@ void syscall_regfunc(void)
		if (!sys_tracepoint_refcount) {
		read_lock(&tasklist_lock);
		for_each_process_thread(p, t) {
		/* Skip kernel threads. */
		if (!(t->flags & PF_KTHREAD))
		set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
		}
		read_unlock(&tasklist_lock);

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