linux-stable.git/tools/perf/util/thread.c, branch linux-4.5.y

perf thread: Fix reference count initial state

2015-12-14T15:08:55+00:00

We should always return from thread__new(), the constructor, with the
object with a reference count of one, so that:

     struct thread *thread = thread__new();
     thread__put(thread);

Will call thread__delete().

If any reference is made to that 'thread' variable, it better use
thread__get(thread) to hold a reference.

We were returning with thread->refcnt set to zero, fix it and some cases
where thread__delete() was being called, which were not a problem
because just one reference was being used, now that we set it to 1, use
thread__put() instead.

Reported-by: Masami Hiramatsu 
Cc: Adrian Hunter 
Cc: David Ahern 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: Wang Nan 
Link: http://lkml.kernel.org/n/tip-4b9mkuk66to4ecckpmpvqx6s@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Avoid deadlock when map_groups are broken

2015-08-19T17:15:09+00:00

Attempting to clone map groups onto themselves will deadlock.

It only happens because of other bugs, but the code should protect
itself anyway.

Reported-by: Linus Torvalds 
Signed-off-by: Adrian Hunter 
Tested-by: Jiri Olsa 
Link: http://lkml.kernel.org/r/1439994561-27436-2-git-send-email-adrian.hunter@intel.com
[ Use pr_debug() instead of dump_fprintf() ]
Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Remove redundant initialization of thread linkage members

2015-05-27T15:21:44+00:00

A thread moves from a rb tree to a list, but can't be on both, because
those linkage members are in a union. This is leftover from when I was
debugging thread refcounting and had nuked that union.

It is harmless duplication, as RB_CLEAR_NODE() does again what
INIT_LIST_HEAD does.

Cc: Adrian Hunter 
Cc: Borislav Petkov 
Cc: David Ahern 
Cc: Don Zickus 
Cc: Frederic Weisbecker 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: Stephane Eranian 
Link: http://lkml.kernel.org/n/tip-hmma9lmip6qlhzhgkhp9tzd1@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

perf machine: Protect the machine->threads with a rwlock

2015-05-08T19:19:27+00:00

In addition to using refcounts for the struct thread lifetime
management, we need to protect access to machine->threads from
concurrent access.

That happens in 'perf top', where a thread processes events, inserting
and deleting entries from that rb_tree while another thread decays
hist_entries, that end up dropping references and ultimately deleting
threads from the rb_tree and releasing its resources when no further
hist_entry (or other data structures, like in 'perf sched') references
it.

So the rule is the same for refcounts + protected trees in the kernel,
get the tree lock, find object, bump the refcount, drop the tree lock,
return, use object, drop the refcount if no more use of it is needed,
keep it if storing it in some other data structure, drop when releasing
that data structure.

I.e. pair "t = machine__find(new)_thread()" with a "thread__put(t)", and
"perf_event__preprocess_sample(&al)" with "addr_location__put(&al)".

The addr_location__put() one is because as we return references to
several data structures, we may end up adding more reference counting
for the other data structures and then we'll drop it at
addr_location__put() time.

Acked-by: David Ahern 
Cc: Adrian Hunter 
Cc: Borislav Petkov 
Cc: Don Zickus 
Cc: Frederic Weisbecker 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: Stephane Eranian 
Link: http://lkml.kernel.org/n/tip-bs9rt4n0jw3hi9f3zxyy3xln@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Use atomic_t to implement thread__{get,put} refcnt

2015-05-08T19:16:23+00:00

Fixing bugs in 'perf top' where the used thread unsafe 'struct thread'
refcount implementation was falling apart because we really use two
threads.

Acked-by: David Ahern 
Cc: Adrian Hunter 
Cc: Borislav Petkov 
Cc: Don Zickus 
Cc: Frederic Weisbecker 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: Stephane Eranian 
Link: http://lkml.kernel.org/n/tip-hil2hol294u5ntcuof4jhmn6@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Remove superfluous thread->comm_set setting

2015-03-12T15:39:50+00:00

It is set by calling thread__set_comm right before the removed line.

Signed-off-by: Jiri Olsa 
Cc: Adrian Hunter 
Cc: Corey Ashford 
Cc: David Ahern 
Cc: Frederic Weisbecker 
Cc: Namhyung Kim 
Cc: Paul Mackerras 
Cc: Peter Zijlstra 
Cc: Stephane Eranian 
Link: http://lkml.kernel.org/r/1425396581-17716-2-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Reference count struct thread

2015-03-03T03:17:08+00:00

We need to do that to stop accumulating entries in the dead_threads
linked list, i.e. we were keeping references to threads in struct hists
that continue to exist even after a thread exited and was removed from
the machine threads rbtree.

We still keep the dead_threads list, but just for debugging, allowing us
to iterate at any given point over the threads that still are referenced
by things like struct hist_entry.

Cc: Adrian Hunter 
Cc: Borislav Petkov 
Cc: David Ahern 
Cc: Don Zickus 
Cc: Frederic Weisbecker 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: Stephane Eranian 
Link: http://lkml.kernel.org/n/tip-3ejvfyed0r7ue61dkurzjux4@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Only override the default :tid comm entry

2014-11-19T15:37:26+00:00

Events may still be ordered even if there are no timestamps e.g. if the
data is recorded per-thread.

Also synthesized COMM events have a timestamp of zero.

Consequently it is better to keep comm entries even if they have a
timestamp of zero.

However, when a struct thread is created the command string is not known
and a comm entry with a string of the form ":" is used.

In that case thread->comm_set is false and the comm entry should be
overridden.

Signed-off-by: Adrian Hunter 
Cc: David Ahern 
Cc: Frederic Weisbecker 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: Paul Mackerras 
Cc: Peter Zijlstra 
Cc: Stephane Eranian 
Link: http://lkml.kernel.org/r/1415715423-15563-4-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Add a thread stack for synthesizing call chains

2014-11-03T20:10:59+00:00

Add a thread stack for synthesizing call chains from call and return
events.

Signed-off-by: Adrian Hunter 
Acked-by: Jiri Olsa 
Cc: David Ahern 
Cc: Frederic Weisbecker 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Cc: Paul Mackerras 
Cc: Peter Zijlstra 
Cc: Stephane Eranian 
Link: http://lkml.kernel.org/r/1414678188-14946-2-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo

perf tools: A thread's machine can be found via thread->mg->machine

2014-10-29T12:32:46+00:00

So stop passing both machine and thread to several thread methods,
reducing function signature length.

Cc: Adrian Hunter 
Cc: Borislav Petkov 
Cc: David Ahern 
Cc: Don Zickus 
Cc: Frederic Weisbecker 
Cc: Jean Pihet 
Cc: Jiri Olsa 
Cc: Mike Galbraith 
Cc: Namhyung Kim 
Cc: Paul Mackerras 
Cc: Peter Zijlstra 
Cc: Stephane Eranian 
Link: http://lkml.kernel.org/n/tip-ckcy19dcp1jfkmdihdjcqdn1@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo