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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 fb45550d76 "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>
This commit is contained in:
Oleg Nesterov 2014-04-13 20:59:38 +02:00 committed by Steven Rostedt
parent 8063e41d2f
commit ea73c79e33
1 changed files with 1 additions and 3 deletions
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4
kernel/tracepoint.c
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@ -497,9 +497,7 @@ void syscall_regfunc(void)
if (!sys_tracepoint_refcount) { if (!sys_tracepoint_refcount) {
read_lock(&tasklist_lock); read_lock(&tasklist_lock);
for_each_process_thread(p, t) { for_each_process_thread(p, t) {
/* Skip kernel threads. */ set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
if (!(t->flags & PF_KTHREAD))
set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
} }
read_unlock(&tasklist_lock); read_unlock(&tasklist_lock);
} }