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Make host ashmem_create_region seed only once.

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Not seeding this each call should help reduce collisions when multiple
threads are calling ashmem_create_region. Also cleaned up code by
deleting gotos, and making formatting consistent.

Bug: 15394258

(cherry picked from commit 1104ae8cfc)

Change-Id: Iafdaea57b2317e0eb7c40d7b5595c523814fd88c
This commit is contained in:
Mathieu Chartier 2014-06-03 10:24:21 -07:00
parent b311ca9ee8
commit 08511d6e31
2 changed files with 69 additions and 67 deletions
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20
libcutils/Android.mk
View file

@ -40,9 +40,6 @@ commonSources := \
iosched_policy.c \
str_parms.c \
commonHostSources := \
ashmem-host.c
# some files must not be compiled when building against Mingw
# they correspond to features not used by our host development tools
# which are also hard or even impossible to port to native Win32
@ -61,13 +58,16 @@ ifneq ($(WINDOWS_HOST_ONLY),1)
commonSources += \
fs.c \
multiuser.c \
socket_inaddr_any_server.c \
socket_local_client.c \
socket_local_server.c \
socket_loopback_client.c \
socket_loopback_server.c \
socket_network_client.c \
sockets.c \
socket_inaddr_any_server.c \
socket_local_client.c \
socket_local_server.c \
socket_loopback_client.c \
socket_loopback_server.c \
socket_network_client.c \
sockets.c \
commonHostSources += \
ashmem-host.c
endif

116
libcutils/ashmem-host.c
View file

@ -22,6 +22,8 @@
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
@ -36,83 +38,83 @@
#define __unused __attribute__((__unused__))
#endif
static pthread_once_t seed_initialized = PTHREAD_ONCE_INIT;
static void initialize_random() {
srand(time(NULL) + getpid());
}
int ashmem_create_region(const char *ignored __unused, size_t size)
{
static const char txt[] = "abcdefghijklmnopqrstuvwxyz"
"ABCDEFGHIJKLMNOPQRSTUVWXYZ";
char name[64];
unsigned int retries = 0;
pid_t pid = getpid();
int fd;
static const char txt[] = "abcdefghijklmnopqrstuvwxyz"
"ABCDEFGHIJKLMNOPQRSTUVWXYZ";
char name[64];
unsigned int retries = 0;
pid_t pid = getpid();
int fd;
if (pthread_once(&seed_initialized, &initialize_random) != 0) {
return -1;
}
do {
/* not beautiful, its just wolf-like loop unrolling */
snprintf(name, sizeof(name), "/tmp/android-ashmem-%d-%c%c%c%c%c%c%c%c",
pid,
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))]);
srand(time(NULL) + pid);
retry:
/* not beautiful, its just wolf-like loop unrolling */
snprintf(name, sizeof(name), "/tmp/android-ashmem-%d-%c%c%c%c%c%c%c%c",
pid,
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))],
txt[(int) ((sizeof(txt) - 1) * (rand() / (RAND_MAX + 1.0)))]);
/* open O_EXCL & O_CREAT: we are either the sole owner or we fail */
fd = open(name, O_RDWR | O_CREAT | O_EXCL, 0600);
if (fd == -1) {
/* unlikely, but if we failed because `name' exists, retry */
if (errno == EEXIST && ++retries < 6)
goto retry;
return -1;
}
/* truncate the file to `len' bytes */
if (ftruncate(fd, size) == -1)
goto error;
if (unlink(name) == -1)
goto error;
return fd;
error:
close(fd);
return -1;
/* open O_EXCL & O_CREAT: we are either the sole owner or we fail */
fd = open(name, O_RDWR | O_CREAT | O_EXCL, 0600);
if (fd == -1) {
/* unlikely, but if we failed because `name' exists, retry */
if (errno != EEXIST || ++retries >= 6) {
return -1;
}
}
} while (fd == -1);
/* truncate the file to `len' bytes */
if (ftruncate(fd, size) != -1 && unlink(name) != -1) {
return fd;
}
close(fd);
return -1;
}
int ashmem_set_prot_region(int fd __unused, int prot __unused)
{
return 0;
return 0;
}
int ashmem_pin_region(int fd __unused, size_t offset __unused, size_t len __unused)
{
return ASHMEM_NOT_PURGED;
return ASHMEM_NOT_PURGED;
}
int ashmem_unpin_region(int fd __unused, size_t offset __unused, size_t len __unused)
{
return ASHMEM_IS_UNPINNED;
return ASHMEM_IS_UNPINNED;
}
int ashmem_get_size_region(int fd)
{
struct stat buf;
int result;
struct stat buf;
int result;
result = fstat(fd, &buf);
if (result == -1) {
return -1;
}
result = fstat(fd, &buf);
if (result == -1) {
return -1;
}
// Check if this is an "ashmem" region.
// TODO: This is very hacky, and can easily break. We need some reliable indicator.
if (!(buf.st_nlink == 0 && S_ISREG(buf.st_mode))) {
errno = ENOTTY;
return -1;
}
// Check if this is an "ashmem" region.
// TODO: This is very hacky, and can easily break. We need some reliable indicator.
if (!(buf.st_nlink == 0 && S_ISREG(buf.st_mode))) {
errno = ENOTTY;
return -1;
}
return (int)buf.st_size; // TODO: care about overflow (> 2GB file)?
return (int)buf.st_size; // TODO: care about overflow (> 2GB file)?
}