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It's not used anywhere in the function.
Link: http://lkml.kernel.org/r/1365553093-10180-1-git-send-email-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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The ftrace_graph_count can be decreased with a "!" pattern, so that
the enabled flag should be updated too.
Link: http://lkml.kernel.org/r/1365663698-2413-1-git-send-email-namhyung@kernel.org
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: stable@vger.kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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As ftrace_filter_lseek is now used with ftrace_pid_fops, it needs to
be moved out of the #ifdef CONFIG_DYNAMIC_FTRACE section as the
ftrace_pid_fops is defined when DYNAMIC_FTRACE is not.
Cc: stable@vger.kernel.org
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Currently set_ftrace_pid and set_graph_function files use seq_lseek
for their fops. However seq_open() is called only for FMODE_READ in
the fops->open() so that if an user tries to seek one of those file
when she open it for writing, it sees NULL seq_file and then panic.
It can be easily reproduced with following command:
$ cd /sys/kernel/debug/tracing
$ echo 1234 | sudo tee -a set_ftrace_pid
In this example, GNU coreutils' tee opens the file with fopen(, "a")
and then the fopen() internally calls lseek().
Link: http://lkml.kernel.org/r/1365663302-2170-1-git-send-email-namhyung@kernel.org
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: stable@vger.kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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The first page was allocated separately, so no need to start from 0.
Link: http://lkml.kernel.org/r/1364820385-32027-2-git-send-email-namhyung@kernel.org
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: stable@vger.kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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On the failure path, stat->start and stat->pages will refer same page.
So it'll attempt to free the same page again and get kernel panic.
Link: http://lkml.kernel.org/r/1364820385-32027-1-git-send-email-namhyung@kernel.org
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: stable@vger.kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Use strlcpy() instead of strncpy() as it will always add a '\0'
to the end of the string even if the buffer is smaller than what
is being copied.
Link: http://lkml.kernel.org/r/51624254.30301@asianux.com
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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The function tracing control loop used by perf spits out a warning
if the called function is not a control function. This is because
the control function references a per cpu allocated data structure
on struct ftrace_ops that is not allocated for other types of
functions.
commit 0a016409e42 "ftrace: Optimize the function tracer list loop"
Had an optimization done to all function tracing loops to optimize
for a single registered ops. Unfortunately, this allows for a slight
race when tracing starts or ends, where the stub function might be
called after the current registered ops is removed. In this case we
get the following dump:
root# perf stat -e ftrace:function sleep 1
[ 74.339105] WARNING: at include/linux/ftrace.h:209 ftrace_ops_control_func+0xde/0xf0()
[ 74.349522] Hardware name: PRIMERGY RX200 S6
[ 74.357149] Modules linked in: sg igb iTCO_wdt ptp pps_core iTCO_vendor_support i7core_edac dca lpc_ich i2c_i801 coretemp edac_core crc32c_intel mfd_core ghash_clmulni_intel dm_multipath acpi_power_meter pcspk
r microcode vhost_net tun macvtap macvlan nfsd kvm_intel kvm auth_rpcgss nfs_acl lockd sunrpc uinput xfs libcrc32c sd_mod crc_t10dif sr_mod cdrom mgag200 i2c_algo_bit drm_kms_helper ttm qla2xxx mptsas ahci drm li
bahci scsi_transport_sas mptscsih libata scsi_transport_fc i2c_core mptbase scsi_tgt dm_mirror dm_region_hash dm_log dm_mod
[ 74.446233] Pid: 1377, comm: perf Tainted: G W 3.9.0-rc1 #1
[ 74.453458] Call Trace:
[ 74.456233] [<ffffffff81062e3f>] warn_slowpath_common+0x7f/0xc0
[ 74.462997] [<ffffffff810fbc60>] ? rcu_note_context_switch+0xa0/0xa0
[ 74.470272] [<ffffffff811041a2>] ? __unregister_ftrace_function+0xa2/0x1a0
[ 74.478117] [<ffffffff81062e9a>] warn_slowpath_null+0x1a/0x20
[ 74.484681] [<ffffffff81102ede>] ftrace_ops_control_func+0xde/0xf0
[ 74.491760] [<ffffffff8162f400>] ftrace_call+0x5/0x2f
[ 74.497511] [<ffffffff8162f400>] ? ftrace_call+0x5/0x2f
[ 74.503486] [<ffffffff8162f400>] ? ftrace_call+0x5/0x2f
[ 74.509500] [<ffffffff810fbc65>] ? synchronize_sched+0x5/0x50
[ 74.516088] [<ffffffff816254d5>] ? _cond_resched+0x5/0x40
[ 74.522268] [<ffffffff810fbc65>] ? synchronize_sched+0x5/0x50
[ 74.528837] [<ffffffff811041a2>] ? __unregister_ftrace_function+0xa2/0x1a0
[ 74.536696] [<ffffffff816254d5>] ? _cond_resched+0x5/0x40
[ 74.542878] [<ffffffff8162402d>] ? mutex_lock+0x1d/0x50
[ 74.548869] [<ffffffff81105c67>] unregister_ftrace_function+0x27/0x50
[ 74.556243] [<ffffffff8111eadf>] perf_ftrace_event_register+0x9f/0x140
[ 74.563709] [<ffffffff816254d5>] ? _cond_resched+0x5/0x40
[ 74.569887] [<ffffffff8162402d>] ? mutex_lock+0x1d/0x50
[ 74.575898] [<ffffffff8111e94e>] perf_trace_destroy+0x2e/0x50
[ 74.582505] [<ffffffff81127ba9>] tp_perf_event_destroy+0x9/0x10
[ 74.589298] [<ffffffff811295d0>] free_event+0x70/0x1a0
[ 74.595208] [<ffffffff8112a579>] perf_event_release_kernel+0x69/0xa0
[ 74.602460] [<ffffffff816254d5>] ? _cond_resched+0x5/0x40
[ 74.608667] [<ffffffff8112a640>] put_event+0x90/0xc0
[ 74.614373] [<ffffffff8112a740>] perf_release+0x10/0x20
[ 74.620367] [<ffffffff811a3044>] __fput+0xf4/0x280
[ 74.625894] [<ffffffff811a31de>] ____fput+0xe/0x10
[ 74.631387] [<ffffffff81083697>] task_work_run+0xa7/0xe0
[ 74.637452] [<ffffffff81014981>] do_notify_resume+0x71/0xb0
[ 74.643843] [<ffffffff8162fa92>] int_signal+0x12/0x17
To fix this a new ftrace_ops flag is added that denotes the ftrace_list_end
ftrace_ops stub as just that, a stub. This flag is now checked in the
control loop and the function is not called if the flag is set.
Thanks to Jovi for not just reporting the bug, but also pointing out
where the bug was in the code.
Link: http://lkml.kernel.org/r/514A8855.7090402@redhat.com
Link: http://lkml.kernel.org/r/1364377499-1900-15-git-send-email-jovi.zhangwei@huawei.com
Tested-by: WANG Chao <chaowang@redhat.com>
Reported-by: WANG Chao <chaowang@redhat.com>
Reported-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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If we reenable ftrace via syctl, we currently set ftrace_trace_function
based on the previous simplistic algorithm. This is inconsistent with
what update_ftrace_function does. So better call that helper instead.
Link: http://lkml.kernel.org/r/5151D26F.1070702@siemens.com
Cc: stable@vger.kernel.org
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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The commit 34600f0e9 "tracing: Fix race with max_tr and changing tracers"
fixed the updating of the main buffers with the race of changing
tracers, but left out the fix to the updating of just a per cpu buffer.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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For NUL terminated string we always need to set '\0' at the end.
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Cc: rostedt@goodmis.org
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/516243B7.9020405@asianux.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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For NUL terminated string we always need to set '\0' at the end.
Signed-off-by: Chen Gang <gang.chen@asianux.com>
Cc: rostedt@goodmis.org
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/51624254.30301@asianux.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Exported so it can be used by bcache's tracepoints
Signed-off-by: Kent Overstreet <koverstreet@google.com>
CC: Steven Rostedt <rostedt@goodmis.org>
CC: Frederic Weisbecker <fweisbec@gmail.com>
CC: Ingo Molnar <mingo@redhat.com>
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Update the README file in debugfs/tracing to something more useful.
What's currently in the file is very old and what it shows doesn't
have much use. Heck, it tells you how to mount debugfs! But to read
this file you would have already needed to mount it.
Replace the file with current up-to-date information. It's rather
limited, but what do you expect from a pseudo README file.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Pull tracing fixes from Steven Rostedt.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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ftrace_dump() had a lot of issues. What ftrace_dump() does, is when
ftrace_dump_on_oops is set (via a kernel parameter or sysctl), it
will dump out the ftrace buffers to the console when either a oops,
panic, or a sysrq-z occurs.
This was written a long time ago when ftrace was fragile to recursion.
But it wasn't written well even for that.
There's a possible deadlock that can occur if a ftrace_dump() is happening
and an NMI triggers another dump. This is because it grabs a lock
before checking if the dump ran.
It also totally disables ftrace, and tracing for no good reasons.
As the ring_buffer now checks if it is read via a oops or NMI, where
there's a chance that the buffer gets corrupted, it will disable
itself. No need to have ftrace_dump() do the same.
ftrace_dump() is now cleaned up where it uses an atomic counter to
make sure only one dump happens at a time. A simple atomic_inc_return()
is enough that is needed for both other CPUs and NMIs. No need for
a spinlock, as if one CPU is running the dump, no other CPU needs
to do it too.
The tracing_on variable is turned off and not turned on. The original
code did this, but it wasn't pretty. By just disabling this variable
we get the result of not seeing traces that happen between crashes.
For sysrq-z, it doesn't get turned on, but the user can always write
a '1' to the tracing_on file. If they are using sysrq-z, then they should
know about tracing_on.
The new code is much easier to read and less error prone. No more
deadlock possibility when an NMI triggers here.
Reported-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Cc: stable@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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trace_event_mutex is an rw semaphore now, not a mutex, change the name.
Link: http://lkml.kernel.org/r/513D843B.40109@huawei.com
Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
[ Forward ported to my new code ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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ppc64 has its own syscall prefix like ".SyS" or ".sys". Make the
comment in arch_syscall_match_sym_name() more understandable.
Link: http://lkml.kernel.org/r/513D842F.40205@huawei.com
Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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trace_destroy_fields() is not used outside of the file. It can be
a static function.
Link: http://lkml.kernel.org/r/513D842A.2000907@huawei.com
Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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By moving find_event_field() and trace_find_field() into trace_events.c,
the ftrace_common_fields list and trace_get_fields() can become local to
the trace_events.c file.
find_event_field() is renamed to trace_find_event_field() to conform to
the tracing global function names.
Link: http://lkml.kernel.org/r/513D8426.9070109@huawei.com
Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
[ rostedt: Modified trace_find_field() to trace_find_event_field() ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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TRACE_MAX_PRINT macro is defined, but is not used.
Link: http://lkml.kernel.org/r/513D8421.4070404@huawei.com
Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Use pr_warn_once, instead of making an open coded implementation.
Link: http://lkml.kernel.org/r/513D8419.20400@huawei.com
Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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When testing my large changes to the ftrace system, there was
a bug that looked like the ring buffer was dropping events.
I wrote up a quick integrity checker of the ring buffer to
see if it was.
Although the bug ended up being something stupid I did in ftrace,
and had nothing to do with the ring buffer, I figured if I spent
the time to write up this test, I might as well include it in the
kernel.
I cleaned it up a bit, as the original version was rather ugly.
Not saying this version is pretty, but it's a beauty queen
compared to what I original wrote.
To enable the start up test, set CONFIG_RING_BUFFER_STARTUP_TEST.
Note, it runs for 10 seconds, so it will slow your boot time
by at least 10 more seconds.
What it does is documented in both the comments and the Kconfig
help.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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The function trace_clock() calls "local_clock()" which is exactly
the same clock that perf uses. I'm not sure why perf doesn't call
trace_clock(), as trace_clock() doesn't have any users.
But now it does. As trace_clock() calls local_clock() like perf does,
I added the trace_clock "perf" option that uses trace_clock().
Now the ftrace buffers can use the same clock as perf uses. This
will be useful when perf starts reading the ftrace buffers, and will
be able to interleave them with the same clock data.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Add a simple trace clock called "uptime" for those that are
interested in the uptime of the trace. It uses jiffies as that's
the safest method, as other uptime clocks grab seq locks, which could
cause a deadlock if taken from an event or function tracer.
Requested-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Currently, the only way to stop the latency tracers from doing function
tracing is to fully disable the function tracer from the proc file
system:
echo 0 > /proc/sys/kernel/ftrace_enabled
This is a big hammer approach as it disables function tracing for
all users. This includes kprobes, perf, stack tracer, etc.
Instead, create a function-trace option that the latency tracers can
check to determine if it should enable function tracing or not.
This option can be set or cleared even while the tracer is active
and the tracers will disable or enable function tracing depending
on how the option was set.
Instead of using the proc file, disable latency function tracing with
echo 0 > /debug/tracing/options/function-trace
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Currently, the depth reported in the stack tracer stack_trace file
does not match the stack_max_size file. This is because the stack_max_size
includes the overhead of stack tracer itself while the depth does not.
The first time a max is triggered, a calculation is not performed that
figures out the overhead of the stack tracer and subtracts it from
the stack_max_size variable. The overhead is stored and is subtracted
from the reported stack size for comparing for a new max.
Now the stack_max_size corresponds to the reported depth:
# cat stack_max_size
4640
# cat stack_trace
Depth Size Location (48 entries)
----- ---- --------
0) 4640 32 _raw_spin_lock+0x18/0x24
1) 4608 112 ____cache_alloc+0xb7/0x22d
2) 4496 80 kmem_cache_alloc+0x63/0x12f
3) 4416 16 mempool_alloc_slab+0x15/0x17
[...]
While testing against and older gcc on x86 that uses mcount instead
of fentry, I found that pasing in ip + MCOUNT_INSN_SIZE let the
stack trace show one more function deep which was missing before.
Cc: stable@vger.kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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When gcc 4.6 on x86 is used, the function tracer will use the new
option -mfentry which does a call to "fentry" at every function
instead of "mcount". The significance of this is that fentry is
called as the first operation of the function instead of the mcount
usage of being called after the stack.
This causes the stack tracer to show some bogus results for the size
of the last function traced, as well as showing "ftrace_call" instead
of the function. This is due to the stack frame not being set up
by the function that is about to be traced.
# cat stack_trace
Depth Size Location (48 entries)
----- ---- --------
0) 4824 216 ftrace_call+0x5/0x2f
1) 4608 112 ____cache_alloc+0xb7/0x22d
2) 4496 80 kmem_cache_alloc+0x63/0x12f
The 216 size for ftrace_call includes both the ftrace_call stack
(which includes the saving of registers it does), as well as the
stack size of the parent.
To fix this, if CC_USING_FENTRY is defined, then the stack_tracer
will reserve the first item in stack_dump_trace[] array when
calling save_stack_trace(), and it will fill it in with the parent ip.
Then the code will look for the parent pointer on the stack and
give the real size of the parent's stack pointer:
# cat stack_trace
Depth Size Location (14 entries)
----- ---- --------
0) 2640 48 update_group_power+0x26/0x187
1) 2592 224 update_sd_lb_stats+0x2a5/0x4ac
2) 2368 160 find_busiest_group+0x31/0x1f1
3) 2208 256 load_balance+0xd9/0x662
I'm Cc'ing stable, although it's not urgent, as it only shows bogus
size for item #0, the rest of the trace is legit. It should still be
corrected in previous stable releases.
Cc: stable@vger.kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Use the stack of stack_trace_call() instead of check_stack() as
the test pointer for max stack size. It makes it a bit cleaner
and a little more accurate.
Adding stable, as a later fix depends on this patch.
Cc: stable@vger.kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Add a function probe that will cause a stack trace to be traced in
the ring buffer when the given function(s) are called.
format is:
<function>:stacktrace[:<count>]
echo 'schedule:stacktrace' > /debug/tracing/set_ftrace_filter
cat /debug/tracing/trace_pipe
kworker/2:0-4329 [002] ...2 2933.558007: <stack trace>
=> kthread
=> ret_from_fork
<idle>-0 [000] .N.2 2933.558019: <stack trace>
=> rest_init
=> start_kernel
=> x86_64_start_reservations
=> x86_64_start_kernel
kworker/2:0-4329 [002] ...2 2933.558109: <stack trace>
=> kthread
=> ret_from_fork
[...]
This can be set to only trace a specific amount of times:
echo 'schedule:stacktrace:3' > /debug/tracing/set_ftrace_filter
cat /debug/tracing/trace_pipe
<...>-58 [003] ...2 841.801694: <stack trace>
=> kthread
=> ret_from_fork
<idle>-0 [001] .N.2 841.801697: <stack trace>
=> start_secondary
<...>-2059 [001] ...2 841.801736: <stack trace>
=> wait_for_common
=> wait_for_completion
=> flush_work
=> tty_flush_to_ldisc
=> input_available_p
=> n_tty_poll
=> tty_poll
=> do_select
=> core_sys_select
=> sys_select
=> system_call_fastpath
To remove these:
echo '!schedule:stacktrace' > /debug/tracing/set_ftrace_filter
echo '!schedule:stacktrace:0' > /debug/tracing/set_ftrace_filter
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Altough the trace_dump_stack() already skips three functions in
the call to stack trace, which gets the stack trace to start
at the caller of the function, the caller may want to skip some
more too (as it may have helper functions).
Add a skip argument to the trace_dump_stack() that lets the caller
skip back tracing functions that it doesn't care about.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Add triggers to function tracer that lets an event get enabled or
disabled when a function is called:
format is:
<function>:enable_event:<system>:<event>[:<count>]
<function>:disable_event:<system>:<event>[:<count>]
echo 'schedule:enable_event:sched:sched_switch' > /debug/tracing/set_ftrace_filter
Every time schedule is called, it will enable the sched_switch event.
echo 'schedule:disable_event:sched:sched_switch:2' > /debug/tracing/set_ftrace_filter
The first two times schedule is called while the sched_switch
event is enabled, it will disable it. It will not count for a time
that the event is already disabled (or enabled for enable_event).
[ fixed return without mutex_unlock() - thanks to Dan Carpenter and smatch ]
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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In order to let triggers enable or disable events, we need a 'soft'
method for doing so. For example, if a function probe is added that
lets a user enable or disable events when a function is called, that
change must be done without taking locks or a mutex, and definitely
it can't sleep. But the full enabling of a tracepoint is expensive.
By adding a 'SOFT_DISABLE' flag, and converting the flags to be updated
without the protection of a mutex (using set/clear_bit()), this soft
disable flag can be used to allow critical sections to enable or disable
events from being traced (after the event has been placed into "SOFT_MODE").
Some caveats though: The comm recorder (to map pids with a comm) can not
be soft disabled (yet). If you disable an event with with a "soft"
disable and wait a while before reading the trace, the comm cache may be
replaced and you'll get a bunch of <...> for comms in the trace.
Reading the "enable" file for an event that is disabled will now give
you "0*" where the '*' denotes that the tracepoint is still active but
the event itself is "disabled".
[ fixed _BIT used in & operation : thanks to Dan Carpenter and smatch ]
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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The entries to the probe hash must be freed after a synchronize_sched()
after the entry has been removed from the hash.
As the entries are registered with ops that may have their own callbacks,
and these callbacks may sleep, we can not use call_rcu_sched() because
the rcu callbacks registered with that are called from a softirq context.
Instead of using call_rcu_sched(), manually save the entries on a free_list
and at the end of the loop that removes the entries, do a synchronize_sched()
and then go through the free_list, freeing the entries.
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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When a function probe is created, each function that the probe is
attached to, a "callback" method is called. On release of the probe,
each function entry calls the "free" method.
First, "callback" is a confusing name and does not really match what
it does. Callback sounds like it will be called when the probe
triggers. But that's not the case. This is really an "init" function,
so lets rename it as such.
Secondly, both "init" and "free" do not pass enough information back
to the handlers. Pass back the ops, ip and data for each time the
method is called. We have the information, might as well use it.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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echo 'schedule:snapshot:1' > /debug/tracing/set_ftrace_filter
This will cause the scheduler to trigger a snapshot the next time
it's called (you can use any function that's not called by NMI).
Even though it triggers only once, you still need to remove it with:
echo '!schedule:snapshot:0' > /debug/tracing/set_ftrace_filter
The :1 can be left off for the first command:
echo 'schedule:snapshot' > /debug/tracing/set_ftrace_filter
But this will cause all calls to schedule to trigger a snapshot.
This must be removed without the ':0'
echo '!schedule:snapshot' > /debug/tracing/set_ftrace_filter
As adding a "count" is a different operation (internally).
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Add alloc_snapshot() and free_snapshot() to allocate and free the
snapshot buffer respectively, and use these to remove duplicate
code.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Currently the function probe enables all functions and runs a "hash"
against every function call to see if it should call a probe. This
is extremely wasteful.
Note, a probe is something like:
echo schedule:traceoff > /debug/tracing/set_ftrace_filter
When schedule is called, the probe will disable tracing. But currently,
it has a call back for *all* functions, and checks to see if the
called function is the probe that is needed.
The probe function has been created before ftrace was rewritten to
allow for more than one "op" to be registered by the function tracer.
When probes were created, it couldn't limit the functions without also
limiting normal function calls. But now we can, it's about time
to update the probe code.
Todo, have separate ops for different entries. That is, assign
a ftrace_ops per probe, instead of one op for all probes. But
as there's not many probes assigned, this may not be that urgent.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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The function tracing probes that trigger traceon or traceoff can be
set to unlimited, or given a count of # of times to execute.
By separating these two types of probes, we can then use the dynamic
ftrace function filtering directly, and remove the brute force
"check if this function called is my probe" routines in ftrace.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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The only thing ftrace_trace_onoff_unreg() does is to do a strcmp()
against the cmd parameter to determine what op to unregister. But
this compare is also done after the location that this function is
called (and returns). By moving the check for '!' to unregister after
the strcmp(), the callback function itself can just do the unregister
and we can get rid of the helper function.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Remove some duplicate code and replace it with a helper function.
This makes the code a it cleaner.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Add EXPORT_SYMBOL_GPL() to let the tracing_snapshot() functions be
called from modules.
Also add a test to see if the snapshot was called from NMI context
and just warn in the tracing buffer if so, and return.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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There's a few places that ftrace uses trace_printk() for internal
use, but this requires context (normal, softirq, irq, NMI) buffers
to keep things lockless. But the trace_puts() does not, as it can
write the string directly into the ring buffer. Make a internal helper
for trace_puts() and have the internal functions use that.
This way the extra context buffers are not used.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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The trace_printk() is extremely fast and is very handy as it can be
used in any context (including NMIs!). But it still requires scanning
the fmt string for parsing the args. Even the trace_bprintk() requires
a scan to know what args will be saved, although it doesn't copy the
format string itself.
Several times trace_printk() has no args, and wastes cpu cycles scanning
the fmt string.
Adding trace_puts() allows the developer to use an even faster
tracing method that only saves the pointer to the string in the
ring buffer without doing any format parsing at all. This will
help remove even more of the "Heisenbug" effect, when debugging.
Also fixed up the F_printk()s for the ftrace internal bprint and print events.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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The changce to add the trace_buffer struct to have the trace array
have both the main buffer and max buffer broke the branch tracer
because the change did not update that code. As the branch tracer
adds a significant amount of overhead, and must be selected via
a selection (not a allyesconfig) it was missed in testing.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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If debugging the kernel, and the developer wants to use
tracing_snapshot() in places where tracing_snapshot_alloc() may
be difficult (or more likely, the developer is lazy and doesn't
want to bother with tracing_snapshot_alloc() at all), then adding
alloc_snapshot
to the kernel command line parameter will tell ftrace to allocate
the snapshot buffer (if configured) when it allocates the main
tracing buffer.
I also noticed that ring_buffer_expanded and tracing_selftest_disabled
had inconsistent use of boolean "true" and "false" with "0" and "1".
I cleaned that up too.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Move the tracing startup selftest code into its own function and
when not enabled, always have that function succeed.
This makes the register_tracer() function much more readable.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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The ring buffer updates when done while the ring buffer is active,
needs to be completed on the CPU that is used for the ring buffer
per_cpu buffer. To accomplish this, schedule_work_on() is used to
schedule work on the given CPU.
Now there's no reason to use schedule_work_on() if the process
doing the update happens to be on the CPU that it is processing.
It has already filled the requirement. Instead, just do the work
and continue.
This is needed for tracing_snapshot_alloc() where it may be called
really early in boot, where the work queues have not been set up yet.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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The new snapshot feature is quite handy. It's a way for the user
to take advantage of the spare buffer that, until then, only
the latency tracers used to "snapshot" the buffer when it hit
a max latency. Now users can trigger a "snapshot" manually when
some condition is hit in a program. But a snapshot currently can
not be triggered by a condition inside the kernel.
With the addition of tracing_snapshot() and tracing_snapshot_alloc(),
snapshots can now be taking when a condition is hit, and the
developer wants to snapshot the case without stopping the trace.
Note, any snapshot will overwrite the old one, so take care
in how this is done.
These new functions are to be used like tracing_on(), tracing_off()
and trace_printk() are. That is, they should never be called
in the mainline Linux kernel. They are solely for the purpose
of debugging.
The tracing_snapshot() will not allocate a buffer, but it is
safe to be called from any context (except NMIs). But if a
snapshot buffer isn't allocated when it is called, it will write
to the live buffer, complaining about the lack of a snapshot
buffer, and then stop tracing (giving you the "permanent snapshot").
tracing_snapshot_alloc() will allocate the snapshot buffer if
it was not already allocated and then take the snapshot. This routine
*may sleep*, and must be called from context that can sleep.
The allocation is done with GFP_KERNEL and not atomic.
If you need a snapshot in an atomic context, say in early boot,
then it is best to call the tracing_snapshot_alloc() before then,
where it will allocate the buffer, and then you can use the
tracing_snapshot() anywhere you want and still get snapshots.
Cc: Hiraku Toyooka <hiraku.toyooka.gu@hitachi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Add a ref count to the trace_array structure and prevent removal
of instances that have open descriptors.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Namhyung Kim
Steven Rostedt (Red Hat)
Chen Gang
Jan Kiszka
Kent Overstreet
Ingo Molnar
zhangwei(Jovi)
Steven Rostedt (Red Hat)