user/sven/linux.git/kernel/trace/trace.c, branch v3.4.48

tracing: Fix ftrace_dump()

2013-05-11T20:48:14Z

commit 7fe70b579c9e3daba71635e31b6189394e7b79d3 upstream. 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: Thomas Gleixner Cc: Peter Zijlstra Cc: Frederic Weisbecker Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman

tracing: Check return value of tracing_init_dentry()

2013-05-08T02:51:54Z

commit ed6f1c996bfe4b6e520cf7a74b51cd6988d84420 upstream. 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 Signed-off-by: Namhyung Kim Cc: Frederic Weisbecker Cc: Namhyung Kim Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman

tracing: Prevent buffer overwrite disabled for latency tracers

2013-04-05T17:04:37Z

commit 613f04a0f51e6e68ac6fe571ab79da3c0a5eb4da upstream. The latency tracers require the buffers to be in overwrite mode, otherwise they get screwed up. Force the buffers to stay in overwrite mode when latency tracers are enabled. Added a flag_changed() method to the tracer structure to allow the tracers to see what flags are being changed, and also be able to prevent the change from happing. [Backported for 3.4-stable. Re-added current_trace NULL checks; removed allocated_snapshot field; adapted to tracing_trace_options_write without trace_set_options.] Signed-off-by: Steven Rostedt Signed-off-by: Lingzhu Xiang Reviewed-by: CAI Qian Signed-off-by: Greg Kroah-Hartman

tracing: Protect tracer flags with trace_types_lock

2013-04-05T17:04:37Z

commit 69d34da2984c95b33ea21518227e1f9470f11d95 upstream. Seems that the tracer flags have never been protected from synchronous writes. Luckily, admins don't usually modify the tracing flags via two different tasks. But if scripts were to be used to modify them, then they could get corrupted. Move the trace_types_lock that protects against tracers changing to also protect the flags being set. [Backported for 3.4, 3.0-stable. Moved return to after unlock.] Signed-off-by: Steven Rostedt Signed-off-by: Lingzhu Xiang Reviewed-by: CAI Qian Signed-off-by: Greg Kroah-Hartman

tracing: Fix race in snapshot swapping

2013-03-28T19:12:06Z

commit 2721e72dd10f71a3ba90f59781becf02638aa0d9 upstream. Although the swap is wrapped with a spin_lock, the assignment of the temp buffer used to swap is not within that lock. It needs to be moved into that lock, otherwise two swaps happening on two different CPUs, can end up using the wrong temp buffer to assign in the swap. Luckily, all current callers of the swap function appear to have their own locks. But in case something is added that allows two different callers to call the swap, then there's a chance that this race can trigger and corrupt the buffers. New code is coming soon that will allow for this race to trigger. I've Cc'd stable, so this bug will not show up if someone backports one of the changes that can trigger this bug. Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman

splice: fix racy pipe->buffers uses

2012-07-16T16:04:42Z

commit 047fe3605235888f3ebcda0c728cb31937eadfe6 upstream. Dave Jones reported a kernel BUG at mm/slub.c:3474! triggered by splice_shrink_spd() called from vmsplice_to_pipe() commit 35f3d14dbbc5 (pipe: add support for shrinking and growing pipes) added capability to adjust pipe->buffers. Problem is some paths don't hold pipe mutex and assume pipe->buffers doesn't change for their duration. Fix this by adding nr_pages_max field in struct splice_pipe_desc, and use it in place of pipe->buffers where appropriate. splice_shrink_spd() loses its struct pipe_inode_info argument. Reported-by: Dave Jones Signed-off-by: Eric Dumazet Cc: Jens Axboe Cc: Alexander Viro Cc: Tom Herbert Tested-by: Dave Jones Signed-off-by: Jens Axboe [bwh: Backported to 3.2: - Adjust context in vmsplice_to_pipe() - Update one more call to splice_shrink_spd(), from skb_splice_bits()] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman

tracing: change CPU ring buffer state from tracing_cpumask

2012-07-16T16:04:40Z

commit 71babb2705e2203a64c27ede13ae3508a0d2c16c upstream. According to Documentation/trace/ftrace.txt: tracing_cpumask: This is a mask that lets the user only trace on specified CPUS. The format is a hex string representing the CPUS. The tracing_cpumask currently doesn't affect the tracing state of per-CPU ring buffers. This patch enables/disables CPU recording as its corresponding bit in tracing_cpumask is set/unset. Link: http://lkml.kernel.org/r/1336096792-25373-3-git-send-email-vnagarnaik@google.com Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Laurent Chavey Cc: Justin Teravest Cc: David Sharp Signed-off-by: Vaibhav Nagarnaik Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman

tracing: Have tracing_off() actually turn tracing off

2012-06-22T18:36:55Z

commit f2bf1f6f5f89d031245067512449fc889b2f4bb2 upstream. A recent update to have tracing_on/off() only affect the ftrace ring buffers instead of all ring buffers had a cut and paste error. The tracing_off() did the exact same thing as tracing_on() and would not actually turn off tracing. Unfortunately, tracing_off() is more important to be working than tracing_on() as this is a key development tool, as it lets the developer turn off tracing as soon as a problem is discovered. It is also used by panic and oops code. This bug also breaks the 'echo func:traceoff > set_ftrace_filter' Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman

tracing: Fix regression with tracing_on

2012-04-16T19:41:28Z

The change to make tracing_on affect only the ftrace ring buffer, caused a bug where it wont affect any ring buffer. The problem was that the buffer of the trace_array was passed to the write function and not the trace array itself. The trace_array can change the buffer when running a latency tracer. If this happens, then the buffer being disabled may not be the buffer currently used by ftrace. This will cause the tracing_on file to become useless. The simple fix is to pass the trace_array to the write function instead of the buffer. Then the actual buffer may be changed. Signed-off-by: Steven Rostedt

tracing: Fix ent_size in trace output

2012-03-27T16:05:44Z

When reading the trace file, the records of each of the per_cpu buffers are examined to find the next event to print out. At the point of looking at the event, the size of the event is recorded. But if the first event is chosen, the other events in the other CPU buffers will reset the event size that is stored in the iterator descriptor, causing the event size passed to the output functions to be incorrect. In most cases this is not a problem, but for the case of stack traces, it is. With the change to the stack tracing to record a dynamic number of back traces, the output depends on the size of the entry instead of the fixed 8 back traces. When the entry size is not correct, the back traces would not be fully printed. Note, reading from the per-cpu trace files were not affected. Reported-by: Thomas Gleixner Tested-by: Thomas Gleixner Cc: stable@vger.kernel.org Signed-off-by: Steven Rostedt