Re: [PATCH v9 1/1] Tracepoint: register/unregister struct tracepoint

[Steven Rostedt <rostedt@goodmis.org>]

On Tue,  1 Apr 2014 18:31:48 -0400
Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:

> Register/unregister tracepoint probes with struct tracepoint pointer
> rather than tracepoint name.
> 
> This change, which vastly simplifies tracepoint.c, has been proposed by
> Steven Rostedt. It also removes 8.8kB (mostly of text) to the vmlinux
> size.
> 
> >From this point on, the tracers need to pass a struct tracepoint pointer
> to probe register/unregister. A probe can now only be connected to a
> tracepoint that exists. Moreover, tracers are responsible for
> unregistering the probe before the module containing its associated
> tracepoint is unloaded.
> 

I applied this and kicked off my tests. It crashed horribly on the
first stress test. Basically the test does this:

perf record -o perf-test.dat -a -- trace-cmd record -e all -p function \
 hackbench 50


[   86.299990] ------------[ cut here ]------------
[   86.304631] WARNING: CPU: 3 PID: 2465 at /home/rostedt/work/git/linux-trace.git/kernel/trace/trace_events.c:226 ftrace_event_reg+0x29/0x92()
[   86.317233] Modules linked in: ipt_MASQUERADE sunrpc ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables uinput snd_hda_codec_idt snd_hda_codec_generic snd_h
da_intel snd_hda_codec snd_hwdep snd_seq snd_seq_device kvm_intel snd_pcm kvm i2c_i801 shpchp snd_timer snd soundcore microcode pata_acpi firewire_ohci firewire_core ata_generic cr
c_itu_t i915 drm_kms_helper drm i2c_algo_bit i2c_core video
[   86.354705] CPU: 3 PID: 2465 Comm: trace-cmd Not tainted 3.14.0-rc7-test+ #337
[   86.361931] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./To be filled by O.E.M., BIOS SDBLI944.86P 05/08/2007
[   86.373225]  ffffffff81c9a630 ffff880077659de0 ffffffff814e556f 0000000000000000
[   86.380739]  ffff880077659e18 ffffffff8103c88f ffffffff810c8f04 ffffffff81a140c0
[   86.388240]  0000000000000000 ffffffff81abb600 ffffffff81ab1290 ffff880077659e28
[   86.395736] Call Trace:
[   86.398201]  [<ffffffff814e556f>] dump_stack+0x4e/0x7a
[   86.403346]  [<ffffffff8103c88f>] warn_slowpath_common+0x7f/0x98
[   86.409359]  [<ffffffff810c8f04>] ? ftrace_event_reg+0x29/0x92
[   86.415198]  [<ffffffff8103c956>] warn_slowpath_null+0x1a/0x1c
[   86.421037]  [<ffffffff810c8f04>] ftrace_event_reg+0x29/0x92
[   86.426702]  [<ffffffff810ca4d9>] __ftrace_event_enable_disable+0xed/0x12e
[   86.433581]  [<ffffffff810ca5e7>] __ftrace_set_clr_event_nolock+0xcd/0xee
[   86.440375]  [<ffffffff810ca68b>] system_enable_write+0x83/0xb6
[   86.446303]  [<ffffffff811208b7>] vfs_write+0xab/0x108
[   86.451445]  [<ffffffff81120fd2>] SyS_write+0x49/0x80
[   86.456509]  [<ffffffff814f1092>] system_call_fastpath+0x16/0x1b
[   86.462517] ---[ end trace 543bc9f6b2135806 ]---

-- Steve