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Subject[PATCH 22/37] perf tools: Protect dso cache tree using dso->lock
Date
The dso cache is accessed during dwarf callchain unwind and it might
be processed concurrently when multi-thread report is enabled.
Protect it under dso->lock.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/util/dso.c | 41 ++++++++++++++++++++++++++++++++---------
1 file changed, 32 insertions(+), 9 deletions(-)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 3da75816b8f8..9555b1772fb5 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -443,10 +443,12 @@ bool dso__data_status_seen(struct dso *dso, enum dso_data_status_seen by)
}

static void
-dso_cache__free(struct rb_root *root)
+dso_cache__free(struct dso *dso)
{
+ struct rb_root *root = &dso->data.cache;
struct rb_node *next = rb_first(root);

+ pthread_mutex_lock(&dso->lock);
while (next) {
struct dso_cache *cache;

@@ -455,14 +457,17 @@ dso_cache__free(struct rb_root *root)
rb_erase(&cache->rb_node, root);
free(cache);
}
+ pthread_mutex_unlock(&dso->lock);
}

-static struct dso_cache *dso_cache__find(const struct rb_root *root, u64 offset)
+static struct dso_cache *dso_cache__find(struct dso *dso, u64 offset)
{
+ const struct rb_root *root = &dso->data.cache;
struct rb_node * const *p = &root->rb_node;
const struct rb_node *parent = NULL;
struct dso_cache *cache;

+ pthread_mutex_lock(&dso->lock);
while (*p != NULL) {
u64 end;

@@ -475,19 +480,24 @@ static struct dso_cache *dso_cache__find(const struct rb_root *root, u64 offset)
else if (offset >= end)
p = &(*p)->rb_right;
else
- return cache;
+ goto out;
}
- return NULL;
+ cache = NULL;
+out:
+ pthread_mutex_unlock(&dso->lock);
+ return cache;
}

-static void
-dso_cache__insert(struct rb_root *root, struct dso_cache *new)
+static struct dso_cache *
+dso_cache__insert(struct dso *dso, struct dso_cache *new)
{
+ struct rb_root *root = &dso->data.cache;
struct rb_node **p = &root->rb_node;
struct rb_node *parent = NULL;
struct dso_cache *cache;
u64 offset = new->offset;

+ pthread_mutex_lock(&dso->lock);
while (*p != NULL) {
u64 end;

@@ -499,10 +509,17 @@ dso_cache__insert(struct rb_root *root, struct dso_cache *new)
p = &(*p)->rb_left;
else if (offset >= end)
p = &(*p)->rb_right;
+ else
+ goto out;
}

rb_link_node(&new->rb_node, parent, p);
rb_insert_color(&new->rb_node, root);
+
+ cache = NULL;
+out:
+ pthread_mutex_unlock(&dso->lock);
+ return cache;
}

static ssize_t
@@ -520,6 +537,7 @@ static ssize_t
dso_cache__read(struct dso *dso, u64 offset, u8 *data, ssize_t size)
{
struct dso_cache *cache;
+ struct dso_cache *old;
ssize_t ret;

do {
@@ -543,7 +561,12 @@ dso_cache__read(struct dso *dso, u64 offset, u8 *data, ssize_t size)

cache->offset = cache_offset;
cache->size = ret;
- dso_cache__insert(&dso->data.cache, cache);
+ old = dso_cache__insert(dso, cache);
+ if (old) {
+ /* we lose the race */
+ free(cache);
+ cache = old;
+ }

ret = dso_cache__memcpy(cache, offset, data, size);

@@ -560,7 +583,7 @@ static ssize_t dso_cache_read(struct dso *dso, u64 offset,
{
struct dso_cache *cache;

- cache = dso_cache__find(&dso->data.cache, offset);
+ cache = dso_cache__find(dso, offset);
if (cache)
return dso_cache__memcpy(cache, offset, data, size);
else
@@ -915,7 +938,7 @@ void dso__delete(struct dso *dso)
}

dso__data_close(dso);
- dso_cache__free(&dso->data.cache);
+ dso_cache__free(dso);
dso__free_a2l(dso);
zfree(&dso->symsrc_filename);
pthread_mutex_destroy(&dso->lock);
--
2.1.3


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