WSL2-Linux-Kernel/kernel/trace
Steven Rostedt (Red Hat) 8a56d7761d ftrace: Fix function graph with loading of modules
Commit 8c4f3c3fa9 "ftrace: Check module functions being traced on reload"
fixed module loading and unloading with respect to function tracing, but
it missed the function graph tracer. If you perform the following

 # cd /sys/kernel/debug/tracing
 # echo function_graph > current_tracer
 # modprobe nfsd
 # echo nop > current_tracer

You'll get the following oops message:

 ------------[ cut here ]------------
 WARNING: CPU: 2 PID: 2910 at /linux.git/kernel/trace/ftrace.c:1640 __ftrace_hash_rec_update.part.35+0x168/0x1b9()
 Modules linked in: nfsd exportfs nfs_acl lockd ipt_MASQUERADE sunrpc ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables uinput snd_hda_codec_idt
 CPU: 2 PID: 2910 Comm: bash Not tainted 3.13.0-rc1-test #7
 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
  0000000000000668 ffff8800787efcf8 ffffffff814fe193 ffff88007d500000
  0000000000000000 ffff8800787efd38 ffffffff8103b80a 0000000000000668
  ffffffff810b2b9a ffffffff81a48370 0000000000000001 ffff880037aea000
 Call Trace:
  [<ffffffff814fe193>] dump_stack+0x4f/0x7c
  [<ffffffff8103b80a>] warn_slowpath_common+0x81/0x9b
  [<ffffffff810b2b9a>] ? __ftrace_hash_rec_update.part.35+0x168/0x1b9
  [<ffffffff8103b83e>] warn_slowpath_null+0x1a/0x1c
  [<ffffffff810b2b9a>] __ftrace_hash_rec_update.part.35+0x168/0x1b9
  [<ffffffff81502f89>] ? __mutex_lock_slowpath+0x364/0x364
  [<ffffffff810b2cc2>] ftrace_shutdown+0xd7/0x12b
  [<ffffffff810b47f0>] unregister_ftrace_graph+0x49/0x78
  [<ffffffff810c4b30>] graph_trace_reset+0xe/0x10
  [<ffffffff810bf393>] tracing_set_tracer+0xa7/0x26a
  [<ffffffff810bf5e1>] tracing_set_trace_write+0x8b/0xbd
  [<ffffffff810c501c>] ? ftrace_return_to_handler+0xb2/0xde
  [<ffffffff811240a8>] ? __sb_end_write+0x5e/0x5e
  [<ffffffff81122aed>] vfs_write+0xab/0xf6
  [<ffffffff8150a185>] ftrace_graph_caller+0x85/0x85
  [<ffffffff81122dbd>] SyS_write+0x59/0x82
  [<ffffffff8150a185>] ftrace_graph_caller+0x85/0x85
  [<ffffffff8150a2d2>] system_call_fastpath+0x16/0x1b
 ---[ end trace 940358030751eafb ]---

The above mentioned commit didn't go far enough. Well, it covered the
function tracer by adding checks in __register_ftrace_function(). The
problem is that the function graph tracer circumvents that (for a slight
efficiency gain when function graph trace is running with a function
tracer. The gain was not worth this).

The problem came with ftrace_startup() which should always be called after
__register_ftrace_function(), if you want this bug to be completely fixed.

Anyway, this solution moves __register_ftrace_function() inside of
ftrace_startup() and removes the need to call them both.

Reported-by: Dave Wysochanski <dwysocha@redhat.com>
Fixes: ed926f9b35 ("ftrace: Use counters to enable functions to trace")
Cc: stable@vger.kernel.org # 3.0+
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2013-11-26 10:36:50 -05:00
..
Kconfig ring-buffer: Select IRQ_WORK 2013-05-03 19:24:17 -04:00
Makefile trace: Stop compiling in trace_clock unconditionally 2012-09-13 22:52:08 -04:00
blktrace.c kernel: trace: blktrace: remove redundent memcpy() in compat_blk_trace_setup() 2013-11-08 09:04:30 -07:00
ftrace.c ftrace: Fix function graph with loading of modules 2013-11-26 10:36:50 -05:00
power-traces.c PM / tracing: remove deprecated power trace API 2013-01-26 00:39:12 +01:00
ring_buffer.c tracing: Typo fix on ring buffer comments 2013-07-18 21:31:26 -04:00
ring_buffer_benchmark.c tracing: Use NUMA allocation for per-cpu ring buffer pages 2011-06-14 22:04:39 -04:00
rpm-traces.c PM / Runtime: Introduce trace points for tracing rpm_* functions 2011-09-27 22:53:27 +02:00
trace.c This batch of changes is mostly clean ups and small bug fixes. 2013-11-16 12:23:18 -08:00
trace.h This batch of changes is mostly clean ups and small bug fixes. 2013-11-16 12:23:18 -08:00
trace_branch.c tracing: Update event filters for multibuffer 2013-11-05 16:50:20 -05:00
trace_clock.c tracing: Add "uptime" trace clock that uses jiffies 2013-03-15 00:36:09 -04:00
trace_entries.h tracing: Add trace_puts() for even faster trace_printk() tracing 2013-03-15 00:35:55 -04:00
trace_event_perf.c perf/ftrace: Fix paranoid level for enabling function tracer 2013-11-06 14:44:49 -05:00
trace_events.c tracing: Do not assign filp->private_data to freed memory 2013-11-06 15:26:54 -05:00
trace_events_filter.c tracing: Update event filters for multibuffer 2013-11-05 16:50:20 -05:00
trace_events_filter_test.h tracing/filter: Add startup tests for events filter 2011-08-19 14:35:59 -04:00
trace_export.c tracing: Update event filters for multibuffer 2013-11-05 16:50:20 -05:00
trace_functions.c tracing: Add ref_data to function and fgraph tracer structs 2013-07-18 21:31:31 -04:00
trace_functions_graph.c tracing: Do not use signed enums with unsigned long long in fgragh output 2013-11-06 15:26:56 -05:00
trace_irqsoff.c tracing: Use flag buffer_disabled for irqsoff tracer 2013-07-01 20:34:28 -04:00
trace_kdb.c tracing: Consolidate max_tr into main trace_array structure 2013-03-15 00:35:40 -04:00
trace_kprobe.c tracing: Update event filters for multibuffer 2013-11-05 16:50:20 -05:00
trace_mmiotrace.c tracing: Update event filters for multibuffer 2013-11-05 16:50:20 -05:00
trace_nop.c tracing/ftrace: make nop-tracer use polling wait for events on pipe 2009-03-23 09:22:15 +01:00
trace_output.c ftrace, sched: Add TRACE_FLAG_PREEMPT_RESCHED 2013-11-11 12:43:39 +01:00
trace_output.h tracing: Rename trace_event_mutex to trace_event_sem 2013-03-15 13:22:10 -04:00
trace_printk.c tracing: Add __tracepoint_string() to export string pointers 2013-07-26 13:39:44 -04:00
trace_probe.c tracing: Replace strict_strto* with kstrto* 2012-10-31 16:45:23 -04:00
trace_probe.h uprobes/tracing: Introduce is_trace_uprobe_enabled() 2013-02-08 18:24:30 +01:00
trace_sched_switch.c tracing: Update event filters for multibuffer 2013-11-05 16:50:20 -05:00
trace_sched_wakeup.c tracing: Add function-trace option to disable function tracing of latency tracers 2013-03-15 00:36:08 -04:00
trace_selftest.c ftrace: Do not run selftest if command line parameter is set 2013-07-01 20:57:15 -04:00
trace_selftest_dynamic.c ftrace: Add self-tests for multiple function trace users 2011-05-18 19:24:51 -04:00
trace_stack.c Tracing updates for Linux 3.10 2013-04-29 13:55:38 -07:00
trace_stat.c trace/trace_stat: use rbtree postorder iteration helper instead of opencoding 2013-11-05 16:01:47 -05:00
trace_stat.h tracing/stat: Add stat_release() callback 2009-07-10 12:14:05 +02:00
trace_syscalls.c tracing: Add support for SOFT_DISABLE to syscall events 2013-11-05 17:48:49 -05:00
trace_uprobe.c tracing: Update event filters for multibuffer 2013-11-05 16:50:20 -05:00