lkml.org 
[lkml]   [2009]   [Sep]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH tracing/kprobes 2/6] ftrace: Fix trace_add_event_call() to initialize list take 2
Steven Rostedt wrote:
> On Wed, 2009-09-16 at 10:17 -0400, Masami Hiramatsu wrote:
>> Steven Rostedt wrote:
>
>>>> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
>>>> index ba34920..38e82a5 100644
>>>> --- a/kernel/trace/trace_events.c
>>>> +++ b/kernel/trace/trace_events.c
>>>> @@ -1009,10 +1009,14 @@ static int __trace_add_event_call(struct ftrace_event_call *call)
>>>> if (!d_events)
>>>> return -ENOENT;
>>>>
>>>> + INIT_LIST_HEAD(&call->list);
>>>
>>> The INIT_LIST_HEAD is not needed here. The list_add will assign it.
>>
>> Without initializing it, list debugging code warns always :-)
>> Please see, __list_add()@lib/list_debug.c
>
> /me looks
>
> from: include/linux/list.h
>
> static inline void list_add(struct list_head *new, struct list_head *head)
> {
> __list_add(new, head, head->next);
> }
>
> from: lib/list_debug.c
>
> void __list_add(struct list_head *new,
> struct list_head *prev,
> struct list_head *next)
> {
> WARN(next->prev != prev,
> "list_add corruption. next->prev should be "
> "prev (%p), but was %p. (next=%p).\n",
> prev, next->prev, next);
> WARN(prev->next != next,
> "list_add corruption. prev->next should be "
> "next (%p), but was %p. (prev=%p).\n",
> next, prev->next, prev);
> next->prev = new;
> new->next = next;
> new->prev = prev;
> prev->next = new;
> }
>
> What you pass in is:
>
> list_add(&call->list,&ftrace_events);
>
> new =&call->list;
> prev =&ftrace_events->prev;
> next =&ftrace_events->next;
>
> The above code never tests "new". The INIT_LIST_HEAD is useless.

Oh, I see, I misunderstood. Thank you for pointing it out. :)
Here, I updated the patch.

---
ftrace: Fix trace_add_event_call() to initialize list
From: Masami Hiramatsu <mhiramat@redhat.com>

Handle failuer path in trace_add_event_call() for fixing below bug
which occurred when I tried to add invalid event twice.

Could not create debugfs 'kmalloc' directory
Failed to register kprobe event: kmalloc
Faild to register probe event(-1)
------------[ cut here ]------------
WARNING: at /home/mhiramat/ksrc/random-tracing/lib/list_debug.c:26
__list_add+0x27/0x5c()
Hardware name:
list_add corruption. next->prev should be prev (c07d78cc), but was
00001000. (next=d854236c).
Modules linked in: sunrpc uinput virtio_net virtio_balloon i2c_piix4 pcspkr
i2c_core virtio_blk virtio_pci virtio_ring virtio [last unloaded:
scsi_wait_scan]
Pid: 1394, comm: tee Not tainted 2.6.31-rc9 #51
Call Trace:
[<c0438424>] warn_slowpath_common+0x65/0x7c
[<c05371b3>] ? __list_add+0x27/0x5c
[<c043846f>] warn_slowpath_fmt+0x24/0x27
[<c05371b3>] __list_add+0x27/0x5c
[<c047f050>] list_add+0xa/0xc
[<c047f8f5>] trace_add_event_call+0x60/0x97
[<c0483133>] command_trace_probe+0x42c/0x51b
[<c044a1b3>] ? remove_wait_queue+0x22/0x27
[<c042a9c0>] ? __wake_up+0x32/0x3b
[<c04832f6>] probes_write+0xd4/0x10a
[<c0483222>] ? probes_write+0x0/0x10a
[<c04b27a9>] vfs_write+0x80/0xdf
[<c04b289c>] sys_write+0x3b/0x5d
[<c0670d41>] syscall_call+0x7/0xb
---[ end trace 2b962b5dc1fdc07d ]---
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Frank Ch. Eigler <fche@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jason Baron <jbaron@redhat.com>
Cc: K.Prasad <prasad@linux.vnet.ibm.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
---
kernel/trace/trace_events.c | 5 ++++-
1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index ba34920..83cc2c0 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1010,9 +1010,12 @@ static int __trace_add_event_call(struct ftrace_event_call *call)
return -ENOENT;

list_add(&call->list, &ftrace_events);
- return event_create_dir(call, d_events, &ftrace_event_id_fops,
+ ret = event_create_dir(call, d_events, &ftrace_event_id_fops,
&ftrace_enable_fops, &ftrace_event_filter_fops,
&ftrace_event_format_fops);
+ if (ret < 0)
+ list_del(&call->list);
+ return ret;
}

/* Add an additional event_call dynamically */

--
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com



\
 
 \ /
  Last update: 2009-09-16 17:43    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site