There is a potential execution path in which variable *ret* is returned
without being properly initialized, previously.
Fix this by initializing variable *ret* to 0.
Link: http://lkml.kernel.org/r/20200205223404.GA3379@embeddedor
Addresses-Coverity-ID: 1491142 ("Uninitialized scalar variable")
Fixes: 2a588dd1d5 ("tracing: Add kprobe event command generation functions")
Reviewed-by: Tom Zanussi <zanussi@kernel.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
As function_graph tracer can run when RCU is not "watching", it can not be
protected by synchronize_rcu() it requires running a task on each CPU before
it can be freed. Calling schedule_on_each_cpu(ftrace_sync) needs to be used.
Link: https://lore.kernel.org/r/20200205131110.GT2935@paulmck-ThinkPad-P72
Cc: stable@vger.kernel.org
Fixes: b9b0c831be ("ftrace: Convert graph filter to use hash tables")
Reported-by: "Paul E. McKenney" <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Because the function graph tracer can execute in sections where RCU is not
"watching", the rcu_dereference_sched() for the has needs to be open coded.
This is fine because the RCU "flavor" of the ftrace hash is protected by
its own RCU handling (it does its own little synchronization on every CPU
and does not rely on RCU sched).
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Fix following instances of sparse error
kernel/trace/ftrace.c:5667:29: error: incompatible types in comparison
kernel/trace/ftrace.c:5813:21: error: incompatible types in comparison
kernel/trace/ftrace.c:5868:36: error: incompatible types in comparison
kernel/trace/ftrace.c:5870:25: error: incompatible types in comparison
Use rcu_dereference_protected to dereference the newly annotated pointer.
Link: http://lkml.kernel.org/r/20200205055701.30195-1-frextrite@gmail.com
Signed-off-by: Amol Grover <frextrite@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Fix following instances of sparse error
kernel/trace/ftrace.c:5664:29: error: incompatible types in comparison
kernel/trace/ftrace.c:5785:21: error: incompatible types in comparison
kernel/trace/ftrace.c:5864:36: error: incompatible types in comparison
kernel/trace/ftrace.c:5866:25: error: incompatible types in comparison
Use rcu_dereference_protected to access the __rcu annotated pointer.
Link: http://lkml.kernel.org/r/20200201072703.17330-1-frextrite@gmail.com
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Amol Grover <frextrite@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
The dynevent_cmd commands that build up the command string don't need
to do that themselves - there's a seq_buf facility that does pretty
much the same thing those command are doing manually, so use it
instead.
Link: http://lkml.kernel.org/r/eb8a6e835c964d0ab8a38cbf5ffa60746b54a465.1580506712.git.zanussi@kernel.org
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
It's kind of strange to have check_arg() callbacks as part of the arg
objects themselves; it makes more sense to just pass these in when the
args are added instead.
Remove the check_arg() callbacks from those objects which also means
removing the check_arg() args from the init functions, adding them to
the add functions and fixing up existing callers.
Link: http://lkml.kernel.org/r/c7708d6f177fcbe1a36b6e4e8e150907df0fa5d2.1580506712.git.zanussi@kernel.org
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
The synth_event trace code contains some almost identical functions
and some small functions that are called only once - consolidate the
common code into single functions and fold in the small functions to
simplify the code overall.
Link: http://lkml.kernel.org/r/d1c8d8ad124a653b7543afe801d38c199ca5c20e.1580506712.git.zanussi@kernel.org
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
The patch 'tracing: Fix histogram code when expression has same var as
value' added code to return an existing variable reference when
creating a new variable reference, which resulted in var_ref_vals
slots being reused instead of being duplicated.
The implementation of the trace action assumes that the end of the
var_ref_vals array starting at action_data.var_ref_idx corresponds to
the values that will be assigned to the trace params. The patch
mentioned above invalidates that assumption, which means that each
param needs to explicitly specify its index into var_ref_vals.
This fix changes action_data.var_ref_idx to an array of var ref
indexes to account for that.
Link: https://lore.kernel.org/r/1580335695.6220.8.camel@kernel.org
Fixes: 8bcebc77e8 ("tracing: Fix histogram code when expression has same var as value")
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Have trace_boot_add_synth_event() use the synth_event interface.
Also, rename synth_event_run_cmd() to synth_event_run_command() now
that trace_boot's version is gone.
Link: http://lkml.kernel.org/r/94f1fa0e31846d0bddca916b8663404b20559e34.1580323897.git.zanussi@kernel.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Move all the tracing selftest configs to the bottom of the tracing menu.
There's no reason for them to be interspersed throughout.
Also, move the bootconfig menu to the top.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Move the config that enables the mmiotracer with the other tracers such that
all the tracers are together.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
The MMIO test module was by itself, move it to the other test modules. Also,
add the text "Test module" to PREEMPTIRQ_DELAY_TEST as that create a test
module as well.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
The features that depend on the function tracer were spread out through the
tracing menu, pull them together as it is easier to manage.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add a test module that checks the basic functionality of the in-kernel
kprobe event command generation API by creating kprobe events from a
module.
Link: http://lkml.kernel.org/r/97e502b204f9dba948e3fa3a4315448298218787.1580323897.git.zanussi@kernel.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Have trace_boot_add_kprobe_event() use the kprobe_event interface.
Also, rename kprobe_event_run_cmd() to kprobe_event_run_command() now
that trace_boot's version is gone.
Link: http://lkml.kernel.org/r/af5429d11291ab1e9a85a0ff944af3b2bcf193c7.1580323897.git.zanussi@kernel.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add functions used to generate kprobe event commands, built on top of
the dynevent_cmd interface.
kprobe_event_gen_cmd_start() is used to create a kprobe event command
using a variable arg list, and kretprobe_event_gen_cmd_start() does
the same for kretprobe event commands. kprobe_event_add_fields() can
be used to add single fields one by one or as a group. Once all
desired fields are added, kprobe_event_gen_cmd_end() or
kretprobe_event_gen_cmd_end() respectively are used to actually
execute the command and create the event.
Link: http://lkml.kernel.org/r/95cc4696502bb6017f9126f306a45ad19b4cc14f.1580323897.git.zanussi@kernel.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add a test module that checks the basic functionality of the in-kernel
synthetic event generation API by generating and tracing synthetic
events from a module.
Link: http://lkml.kernel.org/r/fcb4dd9eb9eefb70ab20538d3529d51642389664.1580323897.git.zanussi@kernel.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add an exported function named synth_event_trace(), allowing modules
or other kernel code to trace synthetic events.
Also added are several functions that allow the same functionality to
be broken out in a piecewise fashion, which are useful in situations
where tracing an event from a full array of values would be
cumbersome. Those functions are synth_event_trace_start/end() and
synth_event_add_(next)_val().
Link: http://lkml.kernel.org/r/7a84de5f1854acf4144b57efe835ca645afa764f.1580323897.git.zanussi@kernel.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add functions used to generate synthetic event commands, built on top
of the dynevent_cmd interface.
synth_event_gen_cmd_start() is used to create a synthetic event
command using a variable arg list and
synth_event_gen_cmd_array_start() does the same thing but using an
array of field descriptors. synth_event_add_field(),
synth_event_add_field_str() and synth_event_add_fields() can be used
to add single fields one by one or as a group. Once all desired
fields are added, synth_event_gen_cmd_end() is used to actually
execute the command and create the event.
synth_event_create() does everything, including creating the event, in
a single call.
Link: http://lkml.kernel.org/r/38fef702fad5ef208009f459552f34a94befd860.1580323897.git.zanussi@kernel.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add an interface used to build up dynamic event creation commands,
such as synthetic and kprobe events. Interfaces specific to those
particular types of events and others can be built on top of this
interface.
Command creation is started by first using the dynevent_cmd_init()
function to initialize the dynevent_cmd object. Following that, args
are appended and optionally checked by the dynevent_arg_add() and
dynevent_arg_pair_add() functions, which use objects representing
arguments and pairs of arguments, initialized respectively by
dynevent_arg_init() and dynevent_arg_pair_init(). Finally, once all
args have been successfully added, the command is finalized and
actually created using dynevent_create().
The code here for actually printing into the dyn_event->cmd buffer
using snprintf() etc was adapted from v4 of Masami's 'tracing/boot:
Add synthetic event support' patch.
Link: http://lkml.kernel.org/r/1f65fa44390b6f238f6036777c3784ced1dcc6a0.1580323897.git.zanussi@kernel.org
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
create_or_delete_synth_event() contains code to delete a synthetic
event, which would be useful on its own - specifically, it would be
useful to allow event-creating modules to call it separately.
Separate out the delete code from that function and create an exported
function named synth_event_delete().
Link: http://lkml.kernel.org/r/050db3b06df7f0a4b8a2922da602d1d879c7c1c2.1580323897.git.zanussi@kernel.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add a function to get an event file and prevent it from going away on
module or instance removal.
trace_get_event_file() will find an event file in a given instance (if
instance is NULL, it assumes the top trace array) and return it,
pinning the instance's trace array as well as the event's module, if
applicable, so they won't go away while in use.
trace_put_event_file() does the matching release.
Link: http://lkml.kernel.org/r/bb31ac4bdda168d5ed3c4b5f5a4c8f633e8d9118.1580323897.git.zanussi@kernel.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
[ Moved trace_array_put() to end of trace_put_event_file() ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Add a new trace_array_find() function that can be used to find a trace
array given the instance name, and replace existing code that does the
same thing with it. Also add trace_array_find_get() which does the
same but returns the trace array after upping its refcount.
Also make both available for use outside of trace.c.
Link: http://lkml.kernel.org/r/cb68528c975eba95bee4561ac67dd1499423b2e5.1580323897.git.zanussi@kernel.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
if seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output.
Without patch:
# dd bs=30 skip=1 if=/sys/kernel/tracing/events/sched/sched_switch/trigger
dd: /sys/kernel/tracing/events/sched/sched_switch/trigger: cannot skip to specified offset
n traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist
# Available triggers:
# traceon traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist
6+1 records in
6+1 records out
206 bytes copied, 0.00027916 s, 738 kB/s
Notice the printing of "# Available triggers:..." after the line.
With the patch:
# dd bs=30 skip=1 if=/sys/kernel/tracing/events/sched/sched_switch/trigger
dd: /sys/kernel/tracing/events/sched/sched_switch/trigger: cannot skip to specified offset
n traceoff snapshot stacktrace enable_event disable_event enable_hist disable_hist hist
2+1 records in
2+1 records out
88 bytes copied, 0.000526867 s, 167 kB/s
It only prints the end of the file, and does not restart.
Link: http://lkml.kernel.org/r/3c35ee24-dd3a-8119-9c19-552ed253388a@virtuozzo.comhttps://bugzilla.kernel.org/show_bug.cgi?id=206283
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
if seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output.
Link: http://lkml.kernel.org/r/7ad85b22-1866-977c-db17-88ac438bc764@virtuozzo.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
[ This is not a bug fix, it just makes it "technically correct"
which is why I applied it. NULL is only returned on an anomaly
which triggers a WARN_ON ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
if seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output.
Without patch:
# dd bs=4 skip=1 if=/sys/kernel/tracing/set_ftrace_pid
dd: /sys/kernel/tracing/set_ftrace_pid: cannot skip to specified offset
id
no pid
2+1 records in
2+1 records out
10 bytes copied, 0.000213285 s, 46.9 kB/s
Notice the "id" followed by "no pid".
With the patch:
# dd bs=4 skip=1 if=/sys/kernel/tracing/set_ftrace_pid
dd: /sys/kernel/tracing/set_ftrace_pid: cannot skip to specified offset
id
0+1 records in
0+1 records out
3 bytes copied, 0.000202112 s, 14.8 kB/s
Notice that it only prints "id" and not the "no pid" afterward.
Link: http://lkml.kernel.org/r/4f87c6ad-f114-30bb-8506-c32274ce2992@virtuozzo.comhttps://bugzilla.kernel.org/show_bug.cgi?id=206283
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Reading the sched_cmdline_ref and sched_tgid_ref initial state within
tracing_start_sched_switch without holding the sched_register_mutex is
racy against concurrent updates, which can lead to tracepoint probes
being registered more than once (and thus trigger warnings within
tracepoint.c).
[ May be the fix for this bug ]
Link: https://lore.kernel.org/r/000000000000ab6f84056c786b93@google.com
Link: http://lkml.kernel.org/r/20190817141208.15226-1-mathieu.desnoyers@efficios.com
Cc: stable@vger.kernel.org
CC: Steven Rostedt (VMware) <rostedt@goodmis.org>
CC: Joel Fernandes (Google) <joel@joelfernandes.org>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Paul E. McKenney <paulmck@linux.ibm.com>
Reported-by: syzbot+774fddf07b7ab29a1e55@syzkaller.appspotmail.com
Fixes: d914ba37d7 ("tracing: Add support for recording tgid of tasks")
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Move external function declarations into kernel/trace/trace.h
from trace_boot.c for tracing subsystem internal use.
Link: http://lkml.kernel.org/r/158029060405.12381.11944554430359702545.stgit@devnote2
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
The 'hist:' prefix gets stripped from the command text during command
processing, but should be added back when displaying the command
during error processing.
Not only because it's what should be displayed but also because not
having it means the test cases fail because the caret is miscalculated
by the length of the prefix string.
Link: http://lkml.kernel.org/r/449df721f560042e22382f67574bcc5b4d830d3d.1561743018.git.zanussi@kernel.org
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
In the process of adding better error messages for sorting, I realized
that strsep was being used incorrectly and some of the error paths I
was expecting to be hit weren't and just fell through to the common
invalid key error case.
It also became obvious that for keyword assignments, it wasn't
necessary to save the full assignment and reparse it later, and having
a common empty-assignment check would also make more sense in terms of
error processing.
Change the code to fix these problems and simplify it for new error
message changes in a subsequent patch.
Link: http://lkml.kernel.org/r/1c3ef0b6655deaf345f6faee2584a0298ac2d743.1561743018.git.zanussi@kernel.org
Fixes: e62347d245 ("tracing: Add hist trigger support for user-defined sorting ('sort=' param)")
Fixes: 7ef224d1d0 ("tracing: Add 'hist' event trigger command")
Fixes: a4072fe85b ("tracing: Add a clock attribute for hist triggers")
Reported-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
As warnings can trigger panics, especially when "panic_on_warn" is set,
memory failure warnings can cause panics and fail fuzz testers that are
stressing memory.
Create a MEM_FAIL() macro to use instead of WARN() in the tracing code
(perhaps this should be a kernel wide macro?), and use that for memory
failure issues. This should stop failing fuzz tests due to warnings.
Link: https://lore.kernel.org/r/CACT4Y+ZP-7np20GVRu3p+eZys9GPtbu+JpfV+HtsufAzvTgJrg@mail.gmail.com
Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
The trace_array_get_by_name() creates a ftrace instance and
trace_array_put() is used to remove the reference. Even though the
trace_array_get_by_name() creates the instance, it also adds a reference
count to it, that prevents user space from removing it.
As the bootconfig just creates the instance on boot up, it should still be
used where it can be deleted by user space after boot. A trace_array_put()
is required to let that happen.
Also, change the documentation on trace_array_get_by_name() to make this not
be so confusing.
Link: https://lore.kernel.org/r/20200124205927.76128804@rorschach.local.home
Fixes: 4f712a4d04 ("tracing/boot: Add instance node support")
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
We checked "iter->trace" earlier so there is no need to check here.
Link: http://lkml.kernel.org/r/20141122183012.GB6994@mwanda
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
[ Pulled from the archeological digging of my INBOX ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
I noticed when trying to use the trace-cmd python interface that reading the raw
buffer wasn't working for kernel_stack events. This is because it uses a
stubbed version of __dynamic_array that doesn't do the __data_loc trick and
encode the length of the array into the field. Instead it just shows up as a
size of 0. So change this to __array and set the len to FTRACE_STACK_ENTRIES
since this is what we actually do in practice and matches how user_stack_trace
works.
Link: http://lkml.kernel.org/r/1411589652-1318-1-git-send-email-jbacik@fb.com
Signed-off-by: Josef Bacik <jbacik@fb.com>
[ Pulled from the archeological digging of my INBOX ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
tracing_stat_init() was always returning '0', even on the error paths. It
now returns -ENODEV if tracing_init_dentry() fails or -ENOMEM if it fails
to created the 'trace_stat' debugfs directory.
Link: http://lkml.kernel.org/r/1410299381-20108-1-git-send-email-luis.henriques@canonical.com
Fixes: ed6f1c996b ("tracing: Check return value of tracing_init_dentry()")
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
[ Pulled from the archeological digging of my INBOX ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Looking through old emails in my INBOX, I came across a patch from Luis
Henriques that attempted to fix a race of two stat tracers registering the
same stat trace (extremely unlikely, as this is done in the kernel, and
probably doesn't even exist). The submitted patch wasn't quite right as it
needed to deal with clean up a bit better (if two stat tracers were the
same, it would have the same files).
But to make the code cleaner, all we needed to do is to keep the
all_stat_sessions_mutex held for most of the registering function.
Link: http://lkml.kernel.org/r/1410299375-20068-1-git-send-email-luis.henriques@canonical.com
Fixes: 002bb86d8d ("tracing/ftrace: separate events tracing and stats tracing engine")
Reported-by: Luis Henriques <luis.henriques@canonical.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This limitation are never lunched from introduce commit 970988e19e
("tracing/kprobe: Add kprobe_event= boot parameter")
Could we remove it if no intention to implement it?
Link: http://lkml.kernel.org/r/1579586075-45132-1-git-send-email-alex.shi@linux.alibaba.com
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
If we exit due to a bad input to trace_printk() (highly unlikely), then the
buffer variable will not be initialized when we unnest the ring buffer.
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
trace_printk() is used to debug the kernel which includes the tracing
infrastructure. But because it writes to the ring buffer, and so does much
of the tracing infrastructure, the ring buffer's recursive detection will
drop writes to the ring buffer that is in the same context as the current
write is happening (it allows interrupts to write when normal context is
writing, but wont let normal context write while normal context is writing).
This can cause confusion and think that the code is where the trace_printk()
exists is not hit. To solve this, up the recursive nesting of the ring
buffer when trace_printk() is called before it writes to the buffer itself.
Note, this does make it dangerous to use trace_printk() in the ring buffer
code itself, because this basically disables the recursion protection of
trace_printk() buffer writes. But as trace_printk() is only used for
debugging, and if this does occur, the developer will see the cause real
quick (recursive blowing up of the stack). Thus the developer can deal with
that. But having trace_printk() silently ignored is a much bigger problem,
and disabling recursive protection is a small price to pay to fix it.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Also fixes a couple of typos
Link: http://lkml.kernel.org/r/1401992525-10417-1-git-send-email-fabf@skynet.be
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Fabian Frederick <fabf@skynet.be>
[ Found this deep in the abyss of my INBOX ]
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
