Revert "bionic: revert to a single (larger) property area"
This reverts commit 5f05348c18286a2cea46eae8acf94ed5b7932fac.
diff --git a/libc/bionic/system_properties.c b/libc/bionic/system_properties.c
index d4054d2..126fea5 100644
--- a/libc/bionic/system_properties.c
+++ b/libc/bionic/system_properties.c
@@ -109,7 +109,7 @@
static const char property_service_socket[] = "/dev/socket/" PROP_SERVICE_NAME;
static char property_filename[PATH_MAX] = PROP_FILENAME;
-prop_area *__system_property_area__ = NULL;
+prop_area *__system_property_regions__[PA_REGION_COUNT] = { NULL, };
const size_t PA_DATA_SIZE = PA_SIZE - sizeof(prop_area);
@@ -124,10 +124,15 @@
return atoi(env);
}
-static int map_prop_area_rw()
+static int map_prop_region_rw(size_t region)
{
prop_area *pa;
int fd;
+ size_t offset = region * PA_SIZE;
+
+ if (__system_property_regions__[region]) {
+ return 0;
+ }
/* dev is a tmpfs that we can use to carve a shared workspace
* out of, so let's do that...
@@ -143,21 +148,24 @@
return -1;
}
- if (ftruncate(fd, PA_SIZE) < 0)
+ if (ftruncate(fd, offset + PA_SIZE) < 0)
goto out;
- pa = mmap(NULL, PA_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+ pa = mmap(NULL, PA_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, offset);
if(pa == MAP_FAILED)
goto out;
memset(pa, 0, PA_SIZE);
pa->magic = PROP_AREA_MAGIC;
pa->version = PROP_AREA_VERSION;
- /* reserve root node */
- pa->bytes_used = sizeof(prop_bt);
+
+ if (!region) {
+ /* reserve root node */
+ pa->bytes_used += sizeof(prop_bt);
+ }
/* plug into the lib property services */
- __system_property_area__ = pa;
+ __system_property_regions__[region] = pa;
close(fd);
return 0;
@@ -179,14 +187,20 @@
int __system_property_area_init()
{
- return map_prop_area_rw();
+ return map_prop_region_rw(0);
}
-static int map_prop_area()
+static int map_prop_region(size_t region)
{
bool fromFile = true;
+ bool swapped;
+ size_t offset = region * PA_SIZE;
int result = -1;
+ if(__system_property_regions__[region]) {
+ return 0;
+ }
+
int fd = open(property_filename, O_RDONLY | O_NOFOLLOW);
if ((fd < 0) && (errno == ENOENT)) {
@@ -215,11 +229,11 @@
if ((fd_stat.st_uid != 0)
|| (fd_stat.st_gid != 0)
|| ((fd_stat.st_mode & (S_IWGRP | S_IWOTH)) != 0)
- || (fd_stat.st_size < PA_SIZE) ) {
+ || (fd_stat.st_size < offset + PA_SIZE) ) {
goto cleanup;
}
- prop_area *pa = mmap(NULL, PA_SIZE, PROT_READ, MAP_SHARED, fd, 0);
+ prop_area *pa = mmap(NULL, PA_SIZE, PROT_READ, MAP_SHARED, fd, offset);
if (pa == MAP_FAILED) {
goto cleanup;
@@ -231,8 +245,16 @@
}
result = 0;
-
- __system_property_area__ = pa;
+ swapped = __sync_bool_compare_and_swap(&__system_property_regions__[region],
+ NULL, pa);
+ if (!swapped) {
+ /**
+ * In the event of a race either mapping is equally good, so
+ * the thread that lost can just throw its mapping away and proceed as
+ * normal.
+ */
+ munmap(pa, PA_SIZE);
+ }
cleanup:
if (fromFile) {
@@ -244,20 +266,33 @@
int __system_properties_init()
{
- return map_prop_area();
+ return map_prop_region(0);
}
static void *new_prop_obj(size_t size, prop_off_t *off)
{
- prop_area *pa = __system_property_area__;
+ prop_area *pa;
+ size_t i, idx;
size = ALIGN(size, sizeof(uint32_t));
- if (pa->bytes_used + size > PA_DATA_SIZE)
+ for (i = 0; i < PA_REGION_COUNT; i++) {
+ int err = map_prop_region_rw(i);
+ if (err < 0) {
+ return NULL;
+ }
+
+ pa = __system_property_regions__[i];
+ if (pa->bytes_used + size <= PA_DATA_SIZE)
+ break;
+ }
+
+ if (i == PA_REGION_COUNT)
return NULL;
- *off = pa->bytes_used;
- __system_property_area__->bytes_used += size;
- return __system_property_area__->data + *off;
+ idx = pa->bytes_used;
+ *off = idx + i * PA_DATA_SIZE;
+ pa->bytes_used += size;
+ return pa->data + idx;
}
static prop_bt *new_prop_bt(const char *name, uint8_t namelen, prop_off_t *off)
@@ -295,10 +330,16 @@
static void *to_prop_obj(prop_off_t off)
{
- if (off > PA_DATA_SIZE)
+ size_t region = off / PA_DATA_SIZE;
+ size_t idx = off % PA_DATA_SIZE;
+
+ if (region > PA_REGION_COUNT)
return NULL;
- return __system_property_area__->data + off;
+ if (map_prop_region(region) < 0)
+ return NULL;
+
+ return __system_property_regions__[region]->data + idx;
}
static prop_bt *root_node()
@@ -529,7 +570,7 @@
{
unsigned n;
if(pi == 0) {
- prop_area *pa = __system_property_area__;
+ prop_area *pa = __system_property_regions__[0];
n = pa->serial;
do {
__futex_wait(&pa->serial, n, 0);
@@ -545,7 +586,7 @@
int __system_property_update(prop_info *pi, const char *value, unsigned int len)
{
- prop_area *pa = __system_property_area__;
+ prop_area *pa = __system_property_regions__[0];
if (len >= PROP_VALUE_MAX)
return -1;
@@ -566,7 +607,7 @@
int __system_property_add(const char *name, unsigned int namelen,
const char *value, unsigned int valuelen)
{
- prop_area *pa = __system_property_area__;
+ prop_area *pa = __system_property_regions__[0];
const prop_info *pi;
if (namelen >= PROP_NAME_MAX)
@@ -592,7 +633,7 @@
unsigned int __system_property_wait_any(unsigned int serial)
{
- prop_area *pa = __system_property_area__;
+ prop_area *pa = __system_property_regions__[0];
do {
__futex_wait(&pa->serial, serial, 0);
diff --git a/libc/include/sys/_system_properties.h b/libc/include/sys/_system_properties.h
index 92e35e1..9c48e1b 100644
--- a/libc/include/sys/_system_properties.h
+++ b/libc/include/sys/_system_properties.h
@@ -42,7 +42,11 @@
#define PROP_SERVICE_NAME "property_service"
#define PROP_FILENAME "/dev/__properties__"
-#define PA_SIZE (128 * 1024)
+/* (4 header words + 28 toc words) = 128 bytes */
+/* 128 bytes header and toc + 28 prop_infos @ 128 bytes = 3712 bytes */
+
+#define PA_REGION_COUNT 128
+#define PA_SIZE 4096
#define SERIAL_VALUE_LEN(serial) ((serial) >> 24)
#define SERIAL_DIRTY(serial) ((serial) & 1)
diff --git a/tests/property_benchmark.cpp b/tests/property_benchmark.cpp
index d10be91..7266bd0 100644
--- a/tests/property_benchmark.cpp
+++ b/tests/property_benchmark.cpp
@@ -23,7 +23,7 @@
#include <vector>
#include <string>
-extern void *__system_property_area__;
+extern void *__system_property_regions__[PA_REGION_COUNT];
#define TEST_NUM_PROPS \
Arg(1)->Arg(4)->Arg(16)->Arg(64)->Arg(128)->Arg(256)->Arg(512)->Arg(1024)
@@ -39,8 +39,10 @@
return;
}
- old_pa = __system_property_area__;
- __system_property_area__ = NULL;
+ for (size_t i = 0; i < PA_REGION_COUNT; i++) {
+ old_pa[i] = __system_property_regions__[i];
+ __system_property_regions__[i] = NULL;
+ }
pa_dirname = dirname;
pa_filename = pa_dirname + "/__properties__";
@@ -77,7 +79,9 @@
if (!valid)
return;
- __system_property_area__ = old_pa;
+ for (size_t i = 0; i < PA_REGION_COUNT; i++) {
+ __system_property_regions__[i] = old_pa[i];
+ }
__system_property_set_filename(PROP_FILENAME);
unlink(pa_filename.c_str());
@@ -103,7 +107,7 @@
private:
std::string pa_dirname;
std::string pa_filename;
- void *old_pa;
+ void *old_pa[PA_REGION_COUNT];
};
static void BM_property_get(int iters, int nprops)
diff --git a/tests/system_properties_test.cpp b/tests/system_properties_test.cpp
index b9256c6..bafd2c3 100644
--- a/tests/system_properties_test.cpp
+++ b/tests/system_properties_test.cpp
@@ -24,7 +24,7 @@
#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
#include <sys/_system_properties.h>
-extern void *__system_property_area__;
+extern void *__system_property_regions__[PA_REGION_COUNT];
struct LocalPropertyTestState {
LocalPropertyTestState() : valid(false) {
@@ -35,8 +35,10 @@
return;
}
- old_pa = __system_property_area__;
- __system_property_area__ = NULL;
+ for (size_t i = 0; i < PA_REGION_COUNT; i++) {
+ old_pa[i] = __system_property_regions__[i];
+ __system_property_regions__[i] = NULL;
+ }
pa_dirname = dirname;
pa_filename = pa_dirname + "/__properties__";
@@ -50,7 +52,9 @@
if (!valid)
return;
- __system_property_area__ = old_pa;
+ for (size_t i = 0; i < PA_REGION_COUNT; i++) {
+ __system_property_regions__[i] = old_pa[i];
+ }
__system_property_set_filename(PROP_FILENAME);
unlink(pa_filename.c_str());
@@ -61,7 +65,7 @@
private:
std::string pa_dirname;
std::string pa_filename;
- void *old_pa;
+ void *old_pa[PA_REGION_COUNT];
};
TEST(properties, add) {
