linux-kernel - [PATCH 2/2] tracing: syscall_regfunc() should not skip kernel threads

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Date:	Sun, 1 Apr 2012 23:38:19 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...hat.com>, Jason Baron <jbaron@...hat.com>,
	linux-kernel@...r.kernel.org,
	Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: [PATCH 2/2] tracing: syscall_regfunc() should not skip kernel
	threads

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

However, this means that a user-space task spawned by
call_usermodehelper() won't report the system calls if
kernel_execve() is called when sys_tracepoint_refcount != 0.

Remove this check. Hopefully the unnecessary report from
ret_from_fork path mentioned by cc3b13c1 is fine. In fact
"this is the only case" is not true. Say, kernel_execve()
itself does "int 80" on X86_32. Hopefully fine too.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 kernel/tracepoint.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index e2a4523..2403e60 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -739,9 +739,7 @@ void syscall_regfunc(void)
 	if (!sys_tracepoint_refcount) {
 		read_lock(&tasklist_lock);
 		do_each_thread(g, t) {
-			/* Skip kernel threads. */
-			if (!(t->flags & PF_KTHREAD))
-				set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
+			set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
 		} while_each_thread(g, t);
 		read_unlock(&tasklist_lock);
 	}
-- 
1.5.5.1


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