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libsuspend: move to exponential backoff

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If for some reason the system can't suspend (usually a driver bug),
libsuspend will currently attempt to retry suspend after 100ms. Because
entering suspend takes a significant amount of CPU time, this can be
extremely expensive and be a major contributor to rapid battery
drain. Move autosuspend to use exponential backoff if the previous
suspend attempt failed.

bug 32092914

Change-Id: I3e9e944f290de5f1853a02e3f61721ba9159df46
This commit is contained in:
Tim Murray 2016-10-11 14:18:27 -07:00
parent 5639d9ad6e
commit fb896944b6
1 changed files with 19 additions and 5 deletions
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24
libsuspend/autosuspend_wakeup_count.c
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@ -21,6 +21,7 @@
#include <stddef.h>
#include <stdbool.h>
#include <string.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
@ -34,12 +35,24 @@
#define SYS_POWER_STATE "/sys/power/state"
#define SYS_POWER_WAKEUP_COUNT "/sys/power/wakeup_count"
#define BASE_SLEEP_TIME 100000
static int state_fd;
static int wakeup_count_fd;
static pthread_t suspend_thread;
static sem_t suspend_lockout;
static const char *sleep_state = "mem";
static void (*wakeup_func)(bool success) = NULL;
static int sleep_time = BASE_SLEEP_TIME;
static void update_sleep_time(bool success) {
if (success) {
sleep_time = BASE_SLEEP_TIME;
return;
}
// double sleep time after each failure up to one minute
sleep_time = MIN(sleep_time * 2, 60000000);
}
static void *suspend_thread_func(void *arg __attribute__((unused)))
{
@ -47,10 +60,12 @@ static void *suspend_thread_func(void *arg __attribute__((unused)))
char wakeup_count[20];
int wakeup_count_len;
int ret;
bool success;
bool success = true;
while (1) {
usleep(100000);
update_sleep_time(success);
usleep(sleep_time);
success = false;
ALOGV("%s: read wakeup_count\n", __func__);
lseek(wakeup_count_fd, 0, SEEK_SET);
wakeup_count_len = TEMP_FAILURE_RETRY(read(wakeup_count_fd, wakeup_count,
@ -74,7 +89,6 @@ static void *suspend_thread_func(void *arg __attribute__((unused)))
continue;
}
success = true;
ALOGV("%s: write %*s to wakeup_count\n", __func__, wakeup_count_len, wakeup_count);
ret = TEMP_FAILURE_RETRY(write(wakeup_count_fd, wakeup_count, wakeup_count_len));
if (ret < 0) {
@ -83,8 +97,8 @@ static void *suspend_thread_func(void *arg __attribute__((unused)))
} else {
ALOGV("%s: write %s to %s\n", __func__, sleep_state, SYS_POWER_STATE);
ret = TEMP_FAILURE_RETRY(write(state_fd, sleep_state, strlen(sleep_state)));
if (ret < 0) {
success = false;
if (ret >= 0) {
success = true;
}
void (*func)(bool success) = wakeup_func;
if (func != NULL) {