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Commit 08511d6e authored by Mathieu Chartier's avatar Mathieu Chartier
Browse files

Make host ashmem_create_region seed only once. 

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 1104ae8c)

Change-Id: Iafdaea57b2317e0eb7c40d7b5595c523814fd88c
parent b311ca9e

libcutils/Android.mk

+10 −10
Original line number Diff line number Diff line
@@ -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
@@ -69,6 +66,9 @@ ifneq ($(WINDOWS_HOST_ONLY),1) 
        socket_network_client.c \

        sockets.c \



    commonHostSources += \

        ashmem-host.c



endif

libcutils/ashmem-host.c

+63 −61
Original line number Diff line number Diff line
@@ -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>
@@ -36,6 +38,11 @@ 
#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"
@@ -44,10 +51,10 @@ int ashmem_create_region(const char *ignored __unused, size_t size) 
    unsigned int retries = 0;

    pid_t pid = getpid();

    int fd;



	srand(time(NULL) + pid);



retry:

    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,
@@ -64,20 +71,15 @@ retry: 
        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;

            if (errno != EEXIST || ++retries >= 6) {

                return -1;

            }



        }

    } while (fd == -1);

    /* truncate the file to `len' bytes */

	if (ftruncate(fd, size) == -1)

		goto error;



	if (unlink(name) == -1)

		goto error;



    if (ftruncate(fd, size) != -1 && unlink(name) != -1) {

        return fd;

error:

    }

    close(fd);

    return -1;

}