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SubjectRe: [PATCH tracing/kprobes 2/6] ftrace: Fix trace_add_event_call() to initialize list
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On Mon, 2009-09-14 at 16:49 -0400, Masami Hiramatsu wrote:
> Initialize event_call.list and 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 | 6 +++++-
> 1 files changed, 5 insertions(+), 1 deletions(-)
>
> 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.


> 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);

But this I can see is needed ;-)

-- Steve

> + return ret;
> }
>
> /* Add an additional event_call dynamically */
>
>



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