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Message-ID: <20150330114907.GH1413@krava>
Date: Mon, 30 Mar 2015 13:49:07 +0200
From: Jiri Olsa <jolsa@...hat.com>
To: David Ahern <dsahern@...il.com>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
Stephane Eranian <eranian@...gle.com>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] segfault in perf-top -- thread refcnt
On Mon, Mar 30, 2015 at 01:21:08PM +0200, Jiri Olsa wrote:
> On Mon, Mar 30, 2015 at 12:22:20PM +0200, Jiri Olsa wrote:
> > On Mon, Mar 30, 2015 at 10:07:37AM +0200, Jiri Olsa wrote:
> >
> > SNIP
> >
> > > >
> > > > 2 things:
> > > > 1. let run for a long time. go about using the server. do lots of builds,
> > > > etc. it takes time
> > > >
> > > > 2. use a box with a LOT of cpus (1024 in my case)
> > > >
> > > > Make sure ulimit is set to get the core.
> > >
> > > reproduced under 24 cpu box with kernel build (make -j25)
> > > running on background.. will try to look closer
> > >
> > > perf: Segmentation fault
> > > -------- backtrace --------
> > > ./perf[0x4fd79b]
> > > /lib64/libc.so.6(+0x358f0)[0x7f9cbff528f0]
> > > ./perf(thread__put+0x5b)[0x4b1a7b]
> > > ./perf(hists__delete_entries+0x70)[0x4c8670]
> > > ./perf[0x436a88]
> > > ./perf[0x4fa73d]
> > > ./perf(perf_evlist__tui_browse_hists+0x97)[0x4fc437]
> > > ./perf[0x4381d0]
> > > /lib64/libpthread.so.0(+0x7ee5)[0x7f9cc1ff2ee5]
> > > /lib64/libc.so.6(clone+0x6d)[0x7f9cc0011b8d]
> > > [0x0]
> >
> > looks like race among __machine__findnew_thread and thread__put
> > over the machine->threads rb_tree insert/removal
> >
> > is there a reason why thread__put does not erase itself from machine->threads?
that was the reason.. we do this separately.. not in thread__put..
is there a reason for this? ;-)
testing attached patch..
jirka
---
diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index f7fb258..966564a 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -60,7 +60,6 @@ static int perf_event__exit_del_thread(struct perf_tool *tool __maybe_unused,
event->fork.ppid, event->fork.ptid);
if (thread) {
- rb_erase(&thread->rb_node, &machine->threads);
if (machine->last_match == thread)
thread__zput(machine->last_match);
thread__put(thread);
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index e335330..a8443ef 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -30,6 +30,7 @@ int machine__init(struct machine *machine, const char *root_dir, pid_t pid)
dsos__init(&machine->kernel_dsos);
machine->threads = RB_ROOT;
+ pthread_mutex_init(&machine->threads_lock, NULL);
INIT_LIST_HEAD(&machine->dead_threads);
machine->last_match = NULL;
@@ -380,10 +381,13 @@ static struct thread *__machine__findnew_thread(struct machine *machine,
if (!create)
return NULL;
- th = thread__new(pid, tid);
+ th = thread__new(machine, pid, tid);
if (th != NULL) {
+
+ pthread_mutex_lock(&machine->threads_lock);
rb_link_node(&th->rb_node, parent, p);
rb_insert_color(&th->rb_node, &machine->threads);
+ pthread_mutex_unlock(&machine->threads_lock);
/*
* We have to initialize map_groups separately
@@ -394,7 +398,9 @@ static struct thread *__machine__findnew_thread(struct machine *machine,
* leader and that would screwed the rb tree.
*/
if (thread__init_map_groups(th, machine)) {
+ pthread_mutex_lock(&machine->threads_lock);
rb_erase(&th->rb_node, &machine->threads);
+ pthread_mutex_unlock(&machine->threads_lock);
thread__delete(th);
return NULL;
}
@@ -1258,7 +1264,6 @@ static void machine__remove_thread(struct machine *machine, struct thread *th)
if (machine->last_match == th)
thread__zput(machine->last_match);
- rb_erase(&th->rb_node, &machine->threads);
/*
* Move it first to the dead_threads list, then drop the reference,
* if this is the last reference, then the thread__delete destructor
diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
index e2faf3b..e3468d6 100644
--- a/tools/perf/util/machine.h
+++ b/tools/perf/util/machine.h
@@ -30,6 +30,7 @@ struct machine {
bool comm_exec;
char *root_dir;
struct rb_root threads;
+ pthread_mutex_t threads_lock;
struct list_head dead_threads;
struct thread *last_match;
struct vdso_info *vdso_info;
diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 1c8fbc9..4592fc4 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -26,7 +26,7 @@ int thread__init_map_groups(struct thread *thread, struct machine *machine)
return thread->mg ? 0 : -1;
}
-struct thread *thread__new(pid_t pid, pid_t tid)
+struct thread *thread__new(struct machine *machine, pid_t pid, pid_t tid)
{
char *comm_str;
struct comm *comm;
@@ -38,6 +38,7 @@ struct thread *thread__new(pid_t pid, pid_t tid)
thread->ppid = -1;
thread->cpu = -1;
INIT_LIST_HEAD(&thread->comm_list);
+ thread->machine = machine;
if (unwind__prepare_access(thread) < 0)
goto err_thread;
@@ -91,7 +92,14 @@ struct thread *thread__get(struct thread *thread)
void thread__put(struct thread *thread)
{
if (thread && --thread->refcnt == 0) {
+ struct machine *machine = thread->machine;
+
list_del_init(&thread->node);
+
+ pthread_mutex_lock(&machine->threads_lock);
+ rb_erase(&thread->rb_node, &machine->threads);
+ pthread_mutex_unlock(&machine->threads_lock);
+
thread__delete(thread);
}
}
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index 9b8a54d..df6fb69 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -31,12 +31,13 @@ struct thread {
void *priv;
struct thread_stack *ts;
+ struct machine *machine;
};
struct machine;
struct comm;
-struct thread *thread__new(pid_t pid, pid_t tid);
+struct thread *thread__new(struct machine *machine, pid_t pid, pid_t tid);
int thread__init_map_groups(struct thread *thread, struct machine *machine);
void thread__delete(struct thread *thread);
--
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