Em Fri, Sep 29, 2017 at 07:47:52AM -0700, kan.liang@intel.com escreveu:

From: Kan Liang <kan.liang@intel.com>

Add two locks to protect namespaces_list and comm_list.

The lock is only needed for multithreaded code, so using mutex wrappers provided by perf tool.

Not all the comm_list/namespaces_list accessing are protected, e.g. thread__exec_comm. Because the multithread code for perf top event synthesizing does not touch them. They don't need a lock.

They don't need a lock _now_, ok I think we can proceed that way, this
cset should serve as a warning to people working in further
multithreading perf.

- Arnaldo

Signed-off-by: Kan Liang <kan.liang@intel.com>
---
tools/perf/util/thread.c | 53 +++++++++++++++++++++++++++++++++++++++++++-----
tools/perf/util/thread.h | 3 +++
2 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index c09bdb5..bf73117 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -45,6 +45,8 @@ struct thread *thread__new(pid_t pid, pid_t tid)
thread->cpu = -1;
INIT_LIST_HEAD(&thread->namespaces_list);
INIT_LIST_HEAD(&thread->comm_list);
+ init_rwsem(&thread->namespaces_lock);
+ init_rwsem(&thread->comm_lock);

comm_str = malloc(32);
if (!comm_str)
@@ -83,18 +85,26 @@ void thread__delete(struct thread *thread)
map_groups__put(thread->mg);
thread->mg = NULL;
}
+ down_write(&thread->namespaces_lock);
list_for_each_entry_safe(namespaces, tmp_namespaces,
&thread->namespaces_list, list) {
list_del(&namespaces->list);
namespaces__free(namespaces);
}
+ up_write(&thread->namespaces_lock);
+
+ down_write(&thread->comm_lock);
list_for_each_entry_safe(comm, tmp_comm, &thread->comm_list, list) {
list_del(&comm->list);
comm__free(comm);
}
+ up_write(&thread->comm_lock);
+
unwind__finish_access(thread);
nsinfo__zput(thread->nsinfo);

+ exit_rwsem(&thread->namespaces_lock);
+ exit_rwsem(&thread->comm_lock);
free(thread);
}

@@ -125,8 +135,8 @@ struct namespaces *thread__namespaces(const struct thread *thread)
return list_first_entry(&thread->namespaces_list, struct namespaces, list);
}

-int thread__set_namespaces(struct thread *thread, u64 timestamp,
- struct namespaces_event *event)
+static int __thread__set_namespaces(struct thread *thread, u64 timestamp,
+ struct namespaces_event *event)
{
struct namespaces *new, *curr = thread__namespaces(thread);

@@ -149,6 +159,17 @@ int thread__set_namespaces(struct thread *thread, u64 timestamp,
return 0;
}

+int thread__set_namespaces(struct thread *thread, u64 timestamp,
+ struct namespaces_event *event)
+{
+ int ret;
+
+ down_write(&thread->namespaces_lock);
+ ret = __thread__set_namespaces(thread, timestamp, event);
+ up_write(&thread->namespaces_lock);
+ return ret;
+}
+
struct comm *thread__comm(const struct thread *thread)
{
if (list_empty(&thread->comm_list))
@@ -170,8 +191,8 @@ struct comm *thread__exec_comm(const struct thread *thread)
return last;
}

-int __thread__set_comm(struct thread *thread, const char *str, u64 timestamp,
- bool exec)
+static int ____thread__set_comm(struct thread *thread, const char *str,
+ u64 timestamp, bool exec)
{
struct comm *new, *curr = thread__comm(thread);

@@ -195,6 +216,17 @@ int __thread__set_comm(struct thread *thread, const char *str, u64 timestamp,
return 0;
}

+int __thread__set_comm(struct thread *thread, const char *str, u64 timestamp,
+ bool exec)
+{
+ int ret;
+
+ down_write(&thread->comm_lock);
+ ret = ____thread__set_comm(thread, str, timestamp, exec);
+ up_write(&thread->comm_lock);
+ return ret;
+}
+
int thread__set_comm_from_proc(struct thread *thread)
{
char path[64];
@@ -212,7 +244,7 @@ int thread__set_comm_from_proc(struct thread *thread)
return err;
}

-const char *thread__comm_str(const struct thread *thread)
+static const char *__thread__comm_str(const struct thread *thread)
{
const struct comm *comm = thread__comm(thread);

@@ -222,6 +254,17 @@ const char *thread__comm_str(const struct thread *thread)
return comm__str(comm);
}

+const char *thread__comm_str(const struct thread *thread)
+{
+ const char *str;
+
+ down_read((struct rw_semaphore *)&thread->comm_lock);
+ str = __thread__comm_str(thread);
+ up_read((struct rw_semaphore *)&thread->comm_lock);
+
+ return str;
+}
+
/* CHECKME: it should probably better return the max comm len from its comm list */
int thread__comm_len(struct thread *thread)
{
diff --git a/tools/perf/util/thread.h b/tools/perf/util/thread.h
index cb1a5dd..10555d6 100644
--- a/tools/perf/util/thread.h
+++ b/tools/perf/util/thread.h
@@ -9,6 +9,7 @@
#include "symbol.h"
#include <strlist.h>
#include <intlist.h>
+#include "rwsem.h"

struct thread_stack;
struct unwind_libunwind_ops;
@@ -29,7 +30,9 @@ struct thread {
int comm_len;
bool dead; /* if set thread has exited */
struct list_head namespaces_list;
+ struct rw_semaphore namespaces_lock;
struct list_head comm_list;
+ struct rw_semaphore comm_lock;
u64 db_id;

void *priv;
--
2.5.5

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