12 Jul, 2013
1 commit
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Pull tracing changes from Steven Rostedt:
"The majority of the changes here are cleanups for the large changes
that were added to 3.10, which includes several bug fixes that have
been marked for stable.As for new features, there were a few, but nothing to write to LWN
about. These include:New function trigger called "dump" and "cpudump" that will cause
ftrace to dump its buffer to the console when the function is called.
The difference between "dump" and "cpudump" is that "dump" will dump
the entire contents of the ftrace buffer, where as "cpudump" will only
dump the contents of the ftrace buffer for the CPU that called the
function.Another small enhancement is a new sysctl switch called
"traceoff_on_warning" which, when enabled, will disable tracing if any
WARN_ON() is triggered. This is useful if you want to debug what
caused a warning and do not want to risk losing your trace data by the
ring buffer overwriting the data before you can disable it. There's
also a kernel command line option that will make this enabled at boot
up called the same thing"* tag 'trace-3.11' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (34 commits)
tracing: Make tracing_open_generic_{tr,tc}() static
tracing: Remove ftrace() function
tracing: Remove TRACE_EVENT_TYPE enum definition
tracing: Make tracer_tracing_{off,on,is_on}() static
tracing: Fix irqs-off tag display in syscall tracing
uprobes: Fix return value in error handling path
tracing: Fix race between deleting buffer and setting events
tracing: Add trace_array_get/put() to event handling
tracing: Get trace_array ref counts when accessing trace files
tracing: Add trace_array_get/put() to handle instance refs better
tracing: Protect ftrace_trace_arrays list in trace_events.c
tracing: Make trace_marker use the correct per-instance buffer
ftrace: Do not run selftest if command line parameter is set
tracing/kprobes: Don't pass addr=ip to perf_trace_buf_submit()
tracing: Use flag buffer_disabled for irqsoff tracer
tracing/kprobes: Turn trace_probe->files into list_head
tracing: Fix disabling of soft disable
tracing: Add missing syscall_metadata comment
tracing: Simplify code for showing of soft disabled flag
tracing/kprobes: Kill probe_enable_lock
...
03 Jul, 2013
3 commits
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I have patches that will use tracing_open_generic_tr/tc() in other
files, but as they are not ready to be merged yet, and Fengguang Wu's
sparse scripts pointed out that these functions were not declared
anywhere, I'll make them static for now.When these functions are required to be used elsewhere, I'll remove
the static then.Reported-by: kbuild test robot
Signed-off-by: Steven Rostedt -
The only caller of function ftrace(...) was removed a long time ago,
so remove the function body as well.Link: http://lkml.kernel.org/r/1365564393-10972-10-git-send-email-jovi.zhangwei@huawei.com
Signed-off-by: zhangwei(Jovi)
Signed-off-by: Steven Rostedt -
I have patches that will use tracer_tracing_on/off/is_on() in other
files, but as they are not ready to be merged yet, and Fengguang Wu's
sparse scripts pointed out that these functions were not declared
anywhere, I'll make them static for now.When these functions are required to be used elsewhere, I'll remove
the static then.Reported-by: kbuild test robot
Signed-off-by: Steven Rostedt
02 Jul, 2013
5 commits
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When a trace file is opened that may access a trace array, it must
increment its ref count to prevent it from being deleted.Cc: stable@vger.kernel.org # 3.10
Reported-by: Alexander Lam
Signed-off-by: Steven Rostedt -
Commit a695cb58162 "tracing: Prevent deleting instances when they are being read"
tried to fix a race between deleting a trace instance and reading contents
of a trace file. But it wasn't good enough. The following could crash the kernel:# cd /sys/kernel/debug/tracing/instances
# ( while :; do mkdir foo; rmdir foo; done ) &
# ( while :; do cat foo/trace &> /dev/null; done ) &Luckily this can only be done by root user, but it should be fixed regardless.
The problem is that a delete of the file can happen after the reader starts
to open the file but before it grabs the trace_types_mutex.The solution is to validate the trace array before using it. If the trace
array does not exist in the list of trace arrays, then it returns -ENODEV.There's a possibility that a trace_array could be deleted and a new one
created and the open would open its file instead. But that is very minor as
it will just return the data of the new trace array, it may confuse the user
but it will not crash the system. As this can only be done by root anyway,
the race will only occur if root is deleting what its trying to read at
the same time.Cc: stable@vger.kernel.org # 3.10
Reported-by: Alexander Lam
Signed-off-by: Steven Rostedt -
There are multiple places where the ftrace_trace_arrays list is accessed in
trace_events.c without the trace_types_lock held.Link: http://lkml.kernel.org/r/1372732674-22726-1-git-send-email-azl@google.com
Cc: Vaibhav Nagarnaik
Cc: David Sharp
Cc: Alexander Z Lam
Cc: stable@vger.kernel.org # 3.10
Signed-off-by: Alexander Z Lam
Signed-off-by: Steven Rostedt -
The trace_marker file was present for each new instance created, but it
added the trace mark to the global trace buffer instead of to
the instance's buffer.Link: http://lkml.kernel.org/r/1372717885-4543-2-git-send-email-azl@google.com
Cc: David Sharp
Cc: Vaibhav Nagarnaik
Cc: Alexander Z Lam
Cc: stable@vger.kernel.org # 3.10
Signed-off-by: Alexander Z Lam
Signed-off-by: Steven Rostedt -
If the ring buffer is disabled and the irqsoff tracer records a trace it
will clear out its buffer and lose the data it had previously recorded.Currently there's a callback when writing to the tracing_of file, but if
tracing is disabled via the function tracer trigger, it will not inform
the irqsoff tracer to stop recording.By using the "mirror" flag (buffer_disabled) in the trace_array, that keeps
track of the status of the trace_array's buffer, it gives the irqsoff
tracer a fast way to know if it should record a new trace or not.
The flag may be a little behind the real state of the buffer, but it
should not affect the trace too much. It's more important for the irqsoff
tracer to be fast.Reported-by: Dave Jones
Signed-off-by: Steven Rostedt
20 Jun, 2013
1 commit
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Add a traceoff_on_warning option in both the kernel command line as well
as a sysctl option. When set, any WARN*() function that is hit will cause
the tracing_on variable to be cleared, which disables writing to the
ring buffer.This is useful especially when tracing a bug with function tracing. When
a warning is hit, the print caused by the warning can flood the trace with
the functions that producing the output for the warning. This can make the
resulting trace useless by either hiding where the bug happened, or worse,
by overflowing the buffer and losing the trace of the bug totally.Acked-by: Peter Zijlstra
Signed-off-by: Steven Rostedt
12 Jun, 2013
2 commits
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Commit 4f271a2a60c748599b30bb4dafff30d770439b96
(tracing: Add a proc file to stop tracing and free buffer)
implement a method to free up ring buffer in kernel memory
in the release code path of free_buffer's fd.Then we don't need read/write support for free_buffer,
indeed we just have a dummy write fop, and don't implement read fop.So the 0200 is more reasonable file mode for free_buffer than
the current file mode 0644.Link: http://lkml.kernel.org/r/20130526085201.GA3183@udknight
Acked-by: Vaibhav Nagarnaik
Acked-by: David Sharp
Signed-off-by: Wang YanQing
Signed-off-by: Steven Rostedt -
Outputting formats of x86-tsc and counter should be a raw format, but after
applying the patch(2b6080f28c7cc3efc8625ab71495aae89aeb63a0), the format was
changed to nanosec. This is because the global variable trace_clock_id was used.
When we use multiple buffers, clock_id of each sub-buffer should be used. Then,
this patch uses tr->clock_id instead of the global variable trace_clock_id.[ Basically, this fixes a regression where the multibuffer code changed the
trace_clock file to update tr->clock_id but the traces still use the old
global trace_clock_id variable, negating the file's effect. The global
trace_clock_id variable is obsolete and removed. - SR ]Link: http://lkml.kernel.org/r/20130423013239.22334.7394.stgit@yunodevel
Signed-off-by: Yoshihiro YUNOMAE
Signed-off-by: Steven Rostedt
07 Jun, 2013
1 commit
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The irqsoff tracer records the max time that interrupts are disabled.
There are hooks in the assembly code that calls back into the tracer when
interrupts are disabled or enabled.When they are enabled, the tracer checks if the amount of time they
were disabled is larger than the previous recorded max interrupts off
time. If it is, it creates a snapshot of the currently running trace
to store where the last largest interrupts off time was held and how
it happened.During testing, this RCU lockdep dump appeared:
[ 1257.829021] ===============================
[ 1257.829021] [ INFO: suspicious RCU usage. ]
[ 1257.829021] 3.10.0-rc1-test+ #171 Tainted: G W
[ 1257.829021] -------------------------------
[ 1257.829021] /home/rostedt/work/git/linux-trace.git/include/linux/rcupdate.h:780 rcu_read_lock() used illegally while idle!
[ 1257.829021]
[ 1257.829021] other info that might help us debug this:
[ 1257.829021]
[ 1257.829021]
[ 1257.829021] RCU used illegally from idle CPU!
[ 1257.829021] rcu_scheduler_active = 1, debug_locks = 0
[ 1257.829021] RCU used illegally from extended quiescent state!
[ 1257.829021] 2 locks held by trace-cmd/4831:
[ 1257.829021] #0: (max_trace_lock){......}, at: [] stop_critical_timing+0x1a3/0x209
[ 1257.829021] #1: (rcu_read_lock){.+.+..}, at: [] __update_max_tr+0x88/0x1ee
[ 1257.829021]
[ 1257.829021] stack backtrace:
[ 1257.829021] CPU: 3 PID: 4831 Comm: trace-cmd Tainted: G W 3.10.0-rc1-test+ #171
[ 1257.829021] 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
[ 1257.829021] 0000000000000001 ffff880065f49da8 ffffffff8153dd2b ffff880065f49dd8
[ 1257.829021] ffffffff81092a00 ffff88006bd78680 ffff88007add7500 0000000000000003
[ 1257.829021] ffff88006bd78680 ffff880065f49e18 ffffffff810daebf ffffffff810dae5a
[ 1257.829021] Call Trace:
[ 1257.829021] [] dump_stack+0x19/0x1b
[ 1257.829021] [] lockdep_rcu_suspicious+0x109/0x112
[ 1257.829021] [] __update_max_tr+0xed/0x1ee
[ 1257.829021] [] ? __update_max_tr+0x88/0x1ee
[ 1257.829021] [] ? user_enter+0xfd/0x107
[ 1257.829021] [] update_max_tr_single+0x11d/0x12d
[ 1257.829021] [] ? user_enter+0xfd/0x107
[ 1257.829021] [] stop_critical_timing+0x141/0x209
[ 1257.829021] [] ? trace_hardirqs_on+0xd/0xf
[ 1257.829021] [] ? user_enter+0xfd/0x107
[ 1257.829021] [] time_hardirqs_on+0x2a/0x2f
[ 1257.829021] [] ? user_enter+0xfd/0x107
[ 1257.829021] [] trace_hardirqs_on_caller+0x16/0x197
[ 1257.829021] [] trace_hardirqs_on+0xd/0xf
[ 1257.829021] [] user_enter+0xfd/0x107
[ 1257.829021] [] do_notify_resume+0x92/0x97
[ 1257.829021] [] int_signal+0x12/0x17What happened was entering into the user code, the interrupts were enabled
and a max interrupts off was recorded. The trace buffer was saved along with
various information about the task: comm, pid, uid, priority, etc.The uid is recorded with task_uid(tsk). But this is a macro that uses rcu_read_lock()
to retrieve the data, and this happened to happen where RCU is blind (user_enter).As only the preempt and irqs off tracers can have this happen, and they both
only have the tsk == current, if tsk == current, use current_uid() instead of
task_uid(), as current_uid() does not use RCU as only current can change its uid.This fixes the RCU suspicious splat.
Signed-off-by: Steven Rostedt
23 May, 2013
1 commit
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If ftrace= is on the kernel command line, when that tracer is
registered, it will be initiated by tracing_set_tracer() to execute that
tracer.The nop tracer is just a stub tracer that is used to have no tracer
enabled. It is assigned at early bootup as it is the default tracer.But if ftrace=nop is on the kernel command line, the registering of the
nop tracer will call tracing_set_tracer() which will try to execute
the nop tracer. But it expects tr->current_trace to be assigned something
as it usually is assigned to the nop tracer. As it hasn't been assigned
to anything yet, it causes the system to crash.The simple fix is to move the tr->current_trace = nop before registering
the nop tracer. The functionality is still the same as the nop tracer
doesn't do anything anyway.Reported-by: Peter Zijlstra
Signed-off-by: Steven Rostedt
30 Apr, 2013
2 commits
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During the 3.10 merge, a conflict happened and the resolution was
almost, but not quite, correct. An if statement was reversed.Signed-off-by: Steven Rostedt
[ Duh. That was just silly of me - Linus ]
Signed-off-by: Linus Torvalds -
Pull tracing updates from Steven Rostedt:
"Along with the usual minor fixes and clean ups there are a few major
changes with this pull request.1) Multiple buffers for the ftrace facility
This feature has been requested by many people over the last few
years. I even heard that Google was about to implement it themselves.
I finally had time and cleaned up the code such that you can now
create multiple instances of the ftrace buffer and have different
events go to different buffers. This way, a low frequency event will
not be lost in the noise of a high frequency event.Note, currently only events can go to different buffers, the tracers
(ie function, function_graph and the latency tracers) still can only
be written to the main buffer.2) The function tracer triggers have now been extended.
The function tracer had two triggers. One to enable tracing when a
function is hit, and one to disable tracing. Now you can record a
stack trace on a single (or many) function(s), take a snapshot of the
buffer (copy it to the snapshot buffer), and you can enable or disable
an event to be traced when a function is hit.3) A perf clock has been added.
A "perf" clock can be chosen to be used when tracing. This will cause
ftrace to use the same clock as perf uses, and hopefully this will
make it easier to interleave the perf and ftrace data for analysis."* tag 'trace-3.10' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (82 commits)
tracepoints: Prevent null probe from being added
tracing: Compare to 1 instead of zero for is_signed_type()
tracing: Remove obsolete macro guard _TRACE_PROFILE_INIT
ftrace: Get rid of ftrace_profile_bits
tracing: Check return value of tracing_init_dentry()
tracing: Get rid of unneeded key calculation in ftrace_hash_move()
tracing: Reset ftrace_graph_filter_enabled if count is zero
tracing: Fix off-by-one on allocating stat->pages
kernel: tracing: Use strlcpy instead of strncpy
tracing: Update debugfs README file
tracing: Fix ftrace_dump()
tracing: Rename trace_event_mutex to trace_event_sem
tracing: Fix comment about prefix in arch_syscall_match_sym_name()
tracing: Convert trace_destroy_fields() to static
tracing: Move find_event_field() into trace_events.c
tracing: Use TRACE_MAX_PRINT instead of constant
tracing: Use pr_warn_once instead of open coded implementation
ring-buffer: Add ring buffer startup selftest
tracing: Bring Documentation/trace/ftrace.txt up to date
tracing: Add "perf" trace_clock
...Conflicts:
kernel/trace/ftrace.c
kernel/trace/trace.c
15 Apr, 2013
1 commit
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Pull perf fixes from Ingo Molnar:
"Misc fixlets"* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf: Fix error return code
ftrace: Fix strncpy() use, use strlcpy() instead of strncpy()
perf: Fix strncpy() use, use strlcpy() instead of strncpy()
perf: Fix strncpy() use, always make sure it's NUL terminated
perf: Fix ring_buffer perf_output_space() boundary calculation
perf/x86: Fix uninitialized pt_regs in intel_pmu_drain_bts_buffer()
13 Apr, 2013
1 commit
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Check return value and bail out if it's NULL.
Link: http://lkml.kernel.org/r/1365553093-10180-2-git-send-email-namhyung@kernel.org
Cc: Frederic Weisbecker
Cc: Namhyung Kim
Cc: stable@vger.kernel.org
Signed-off-by: Namhyung Kim
Signed-off-by: Steven Rostedt
09 Apr, 2013
2 commits
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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
Signed-off-by: Steven Rostedt -
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
08 Apr, 2013
1 commit
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For NUL terminated string we always need to set '\0' at the end.
Signed-off-by: Chen Gang
Cc: rostedt@goodmis.org
Cc: Frederic Weisbecker
Link: http://lkml.kernel.org/r/51624254.30301@asianux.com
Signed-off-by: Ingo Molnar
21 Mar, 2013
1 commit
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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
16 Mar, 2013
3 commits
-
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)
Cc: stable@vger.kernel.org
Cc: Thomas Gleixner
Cc: Peter Zijlstra
Cc: Frederic Weisbecker
Signed-off-by: Steven Rostedt -
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)
Signed-off-by: Steven Rostedt -
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)
Signed-off-by: Steven Rostedt
15 Mar, 2013
15 commits
-
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
Cc: Peter Zijlstra
Cc: Frederic Weisbecker
Signed-off-by: Steven Rostedt -
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
Cc: Thomas Gleixner
Cc: Frederic Weisbecker
Signed-off-by: Steven Rostedt -
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
Cc: Peter Zijlstra
Cc: Frederic Weisbecker
Cc: Clark Williams
Cc: John Kacur
Signed-off-by: Steven Rostedt -
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
-
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
-
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
-
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
-
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
-
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
Cc: Peter Zijlstra
Cc: Frederic Weisbecker
Signed-off-by: Steven Rostedt -
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 addingalloc_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
-
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
-
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
Cc: Thomas Gleixner
Cc: Peter Zijlstra
Signed-off-by: Steven Rostedt -
Add a ref count to the trace_array structure and prevent removal
of instances that have open descriptors.Signed-off-by: Steven Rostedt
-
Add the per_cpu directory to the created tracing instances:
cd /sys/kernel/debug/tracing/instances
mkdir foo
ls foo/per_cpu/cpu0
buffer_size_kb snapshot_raw trace trace_pipe_raw
snapshot stats trace_pipeSigned-off-by: Steven Rostedt
-
Add the "snapshot" file to the the multi-buffer instances.
cd /sys/kernel/debug/tracing/instances
mkdir foo
ls foo
buffer_size_kb buffer_total_size_kb events free_buffer set_event
snapshot trace trace_clock trace_marker trace_options trace_pipe
tracing_on
cat foo/snapshot
# tracer: nop
#
#
# * Snapshot is freed *
#
# Snapshot commands:
# echo 0 > snapshot : Clears and frees snapshot buffer
# echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.
# Takes a snapshot of the main buffer.
# echo 2 > snapshot : Clears snapshot buffer (but does not allocate)
# (Doesn't have to be '2' works with any number that
# is not a '0' or '1')Signed-off-by: Steven Rostedt
