[for-next][PATCH 2/3] tracing: Change syscall_*regfunc() to check PF_KTHREAD and use for_each_process_thread()

Steven Rostedt
2014-06-19T01:42:05Z

[-- Attachment #1: 0002-tracing-Change-syscall_-regfunc-to-check-PF_KTHREAD-.patch --]
[-- Type: text/plain, Size: 2121 bytes --]

From: Oleg Nesterov <oleg@redhat.com>

1. Remove _irqsafe from syscall_regfunc/syscall_unregfunc,
read_lock(tasklist) doesn't need to disable irqs.

2. Change this code to avoid the deprecated do_each_thread()
and use for_each_process_thread() (stolen from the patch
from Frederic).

3. Change syscall_regfunc() to check PF_KTHREAD to skip
the kernel threads, ->mm != NULL is the common mistake.

Note: probably this check should be simply removed, needs
another patch.

[fweisbec@gmail.com: s/do_each_thread/for_each_process_thread/]
Link: http://lkml.kernel.org/p/20140413185918.GC20668@redhat.com

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/tracepoint.c | 24 +++++++++++-------------
1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 33cbd8c203f8..9cf12640de5a 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -492,33 +492,31 @@ static int sys_tracepoint_refcount;

void syscall_regfunc(void)
{
- unsigned long flags;
- struct task_struct *g, *t;
+ struct task_struct *p, *t;

if (!sys_tracepoint_refcount) {
- read_lock_irqsave(&tasklist_lock, flags);
- do_each_thread(g, t) {
+ read_lock(&tasklist_lock);
+ for_each_process_thread(p, t) {
/* Skip kernel threads. */
- if (t->mm)
+ if (!(t->flags & PF_KTHREAD))
set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
- } while_each_thread(g, t);
- read_unlock_irqrestore(&tasklist_lock, flags);
+ }
+ read_unlock(&tasklist_lock);
}
sys_tracepoint_refcount++;
}

void syscall_unregfunc(void)
{
- unsigned long flags;
- struct task_struct *g, *t;
+ struct task_struct *p, *t;

sys_tracepoint_refcount--;
if (!sys_tracepoint_refcount) {
- read_lock_irqsave(&tasklist_lock, flags);
- do_each_thread(g, t) {
+ read_lock(&tasklist_lock);
+ for_each_process_thread(p, t) {
clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
- } while_each_thread(g, t);
- read_unlock_irqrestore(&tasklist_lock, flags);
+ }
+ read_unlock(&tasklist_lock);
}
}
#endif
--
2.0.0.rc2