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Commit fb896944 authored by Tim Murray's avatar Tim Murray
Browse files

libsuspend: move to exponential backoff 

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
parent 5639d9ad

libsuspend/autosuspend_wakeup_count.c

+19 −5
Original line number Diff line number Diff line
@@ -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) {