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Subject[PATCH 26/38] perf tools: Protect dso cache fd with a mutex
Date
When dso cache is accessed in multi-thread environment, it's possible
to close other dso->data.fd during operation due to open file limit.
Protect the file descriptors using a separate mutex.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/util/dso.c | 98 +++++++++++++++++++++++++++++++++++++--------------
1 file changed, 72 insertions(+), 26 deletions(-)

diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 3bfbe0e76e96..64aaa45dcdd7 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -213,6 +213,7 @@ bool dso__needs_decompress(struct dso *dso)
*/
static LIST_HEAD(dso__data_open);
static long dso__data_open_cnt;
+static pthread_mutex_t dso__data_open_lock = PTHREAD_MUTEX_INITIALIZER;

static void dso__list_add(struct dso *dso)
{
@@ -382,7 +383,9 @@ static void check_data_close(void)
*/
void dso__data_close(struct dso *dso)
{
+ pthread_mutex_lock(&dso__data_open_lock);
close_dso(dso);
+ pthread_mutex_unlock(&dso__data_open_lock);
}

/**
@@ -405,6 +408,8 @@ int dso__data_fd(struct dso *dso, struct machine *machine)
if (dso->data.status == DSO_DATA_STATUS_ERROR)
return -1;

+ pthread_mutex_lock(&dso__data_open_lock);
+
if (dso->data.fd >= 0)
goto out;

@@ -427,6 +432,7 @@ int dso__data_fd(struct dso *dso, struct machine *machine)
else
dso->data.status = DSO_DATA_STATUS_ERROR;

+ pthread_mutex_unlock(&dso__data_open_lock);
return dso->data.fd;
}

@@ -531,7 +537,8 @@ dso_cache__memcpy(struct dso_cache *cache, u64 offset,
}

static ssize_t
-dso_cache__read(struct dso *dso, u64 offset, u8 *data, ssize_t size)
+dso_cache__read(struct dso *dso, struct machine *machine,
+ u64 offset, u8 *data, ssize_t size)
{
struct dso_cache *cache;
struct dso_cache *old;
@@ -540,11 +547,24 @@ dso_cache__read(struct dso *dso, u64 offset, u8 *data, ssize_t size)
do {
u64 cache_offset;

- ret = -ENOMEM;
-
cache = zalloc(sizeof(*cache) + DSO__DATA_CACHE_SIZE);
if (!cache)
- break;
+ return -ENOMEM;
+
+ pthread_mutex_lock(&dso__data_open_lock);
+
+ /*
+ * dso->data.fd might be closed if other thread opened another
+ * file (dso) due to open file limit (RLIMIT_NOFILE).
+ */
+ if (dso->data.fd < 0) {
+ dso->data.fd = open_dso(dso, machine);
+ if (dso->data.fd < 0) {
+ ret = -errno;
+ dso->data.status = DSO_DATA_STATUS_ERROR;
+ break;
+ }
+ }

cache_offset = offset & DSO__DATA_CACHE_MASK;

@@ -554,6 +574,11 @@ dso_cache__read(struct dso *dso, u64 offset, u8 *data, ssize_t size)

cache->offset = cache_offset;
cache->size = ret;
+ } while (0);
+
+ pthread_mutex_unlock(&dso__data_open_lock);
+
+ if (ret > 0) {
old = dso_cache__insert(dso, cache);
if (old) {
/* we lose the race */
@@ -562,8 +587,7 @@ dso_cache__read(struct dso *dso, u64 offset, u8 *data, ssize_t size)
}

ret = dso_cache__memcpy(cache, offset, data, size);
-
- } while (0);
+ }

if (ret <= 0)
free(cache);
@@ -571,8 +595,8 @@ dso_cache__read(struct dso *dso, u64 offset, u8 *data, ssize_t size)
return ret;
}

-static ssize_t dso_cache_read(struct dso *dso, u64 offset,
- u8 *data, ssize_t size)
+static ssize_t dso_cache_read(struct dso *dso, struct machine *machine,
+ u64 offset, u8 *data, ssize_t size)
{
struct dso_cache *cache;

@@ -580,7 +604,7 @@ static ssize_t dso_cache_read(struct dso *dso, u64 offset,
if (cache)
return dso_cache__memcpy(cache, offset, data, size);
else
- return dso_cache__read(dso, offset, data, size);
+ return dso_cache__read(dso, machine, offset, data, size);
}

/*
@@ -588,7 +612,8 @@ static ssize_t dso_cache_read(struct dso *dso, u64 offset,
* in the rb_tree. Any read to already cached data is served
* by cached data.
*/
-static ssize_t cached_read(struct dso *dso, u64 offset, u8 *data, ssize_t size)
+static ssize_t cached_read(struct dso *dso, struct machine *machine,
+ u64 offset, u8 *data, ssize_t size)
{
ssize_t r = 0;
u8 *p = data;
@@ -596,7 +621,7 @@ static ssize_t cached_read(struct dso *dso, u64 offset, u8 *data, ssize_t size)
do {
ssize_t ret;

- ret = dso_cache_read(dso, offset, p, size);
+ ret = dso_cache_read(dso, machine, offset, p, size);
if (ret < 0)
return ret;

@@ -616,21 +641,42 @@ static ssize_t cached_read(struct dso *dso, u64 offset, u8 *data, ssize_t size)
return r;
}

-static int data_file_size(struct dso *dso)
+static int data_file_size(struct dso *dso, struct machine *machine)
{
+ int ret = 0;
struct stat st;
char sbuf[STRERR_BUFSIZE];

- if (!dso->data.file_size) {
- if (fstat(dso->data.fd, &st)) {
- pr_err("dso mmap failed, fstat: %s\n",
- strerror_r(errno, sbuf, sizeof(sbuf)));
- return -1;
+ if (dso->data.file_size)
+ return 0;
+
+ pthread_mutex_lock(&dso__data_open_lock);
+
+ /*
+ * dso->data.fd might be closed if other thread opened another
+ * file (dso) due to open file limit (RLIMIT_NOFILE).
+ */
+ if (dso->data.fd < 0) {
+ dso->data.fd = open_dso(dso, machine);
+ if (dso->data.fd < 0) {
+ ret = -errno;
+ dso->data.status = DSO_DATA_STATUS_ERROR;
+ goto out;
}
- dso->data.file_size = st.st_size;
}

- return 0;
+ if (fstat(dso->data.fd, &st) < 0) {
+ ret = -errno;
+ pr_err("dso cache fstat failed: %s\n",
+ strerror_r(errno, sbuf, sizeof(sbuf)));
+ dso->data.status = DSO_DATA_STATUS_ERROR;
+ goto out;
+ }
+ dso->data.file_size = st.st_size;
+
+out:
+ pthread_mutex_unlock(&dso__data_open_lock);
+ return ret;
}

/**
@@ -648,17 +694,17 @@ off_t dso__data_size(struct dso *dso, struct machine *machine)
if (fd < 0)
return fd;

- if (data_file_size(dso))
+ if (data_file_size(dso, machine))
return -1;

/* For now just estimate dso data size is close to file size */
return dso->data.file_size;
}

-static ssize_t data_read_offset(struct dso *dso, u64 offset,
- u8 *data, ssize_t size)
+static ssize_t data_read_offset(struct dso *dso, struct machine *machine,
+ u64 offset, u8 *data, ssize_t size)
{
- if (data_file_size(dso))
+ if (data_file_size(dso, machine))
return -1;

/* Check the offset sanity. */
@@ -668,7 +714,7 @@ static ssize_t data_read_offset(struct dso *dso, u64 offset,
if (offset + size < offset)
return -1;

- return cached_read(dso, offset, data, size);
+ return cached_read(dso, machine, offset, data, size);
}

/**
@@ -685,10 +731,10 @@ static ssize_t data_read_offset(struct dso *dso, u64 offset,
ssize_t dso__data_read_offset(struct dso *dso, struct machine *machine,
u64 offset, u8 *data, ssize_t size)
{
- if (dso__data_fd(dso, machine) < 0)
+ if (dso->data.status == DSO_DATA_STATUS_ERROR)
return -1;

- return data_read_offset(dso, offset, data, size);
+ return data_read_offset(dso, machine, offset, data, size);
}

/**
--
2.2.2


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