Messages in this thread Patch in this message |  | | | Date | Wed, 16 Sep 2009 11:42:55 -0400 | | From | Masami Hiramatsu <> | | Subject | [PATCH tracing/kprobes 2/6] ftrace: Fix trace_add_event_call() to initialize list take 2 |
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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
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