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lmkd: Use process_mrelease to reap the target process from a thread am: 7c3addb2a1 

Original change: https://android-review.googlesource.com/c/platform/system/memory/lmkd/+/1904583

Change-Id: I21a13a46890d2eee9ddd66cbeaec1c8f3e9317f4
This commit is contained in:
Suren Baghdasaryan 2022-01-06 22:02:57 +00:00 committed by Automerger Merge Worker
parent 53df06cdf1 7c3addb2a1
commit c4067fc9f2
4 changed files with 398 additions and 59 deletions
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5
Android.bp
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@ -12,7 +12,10 @@ cc_defaults {
cc_binary {
name: "lmkd",
srcs: ["lmkd.cpp"],
srcs: [
"lmkd.cpp",
"reaper.cpp",
],
shared_libs: [
"libcutils",
"liblog",

145
lmkd.cpp
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@ -16,12 +16,10 @@
#define LOG_TAG "lowmemorykiller"
#include <dirent.h>
#include <errno.h>
#include <inttypes.h>
#include <pwd.h>
#include <sched.h>
#include <signal.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
@ -30,12 +28,9 @@
#include <sys/eventfd.h>
#include <sys/mman.h>
#include <sys/pidfd.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/sysinfo.h>
#include <sys/time.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
@ -47,10 +42,9 @@
#include <log/log_event_list.h>
#include <log/log_time.h>
#include <private/android_filesystem_config.h>
#include <processgroup/processgroup.h>
#include <psi/psi.h>
#include <system/thread_defs.h>
#include "reaper.h"
#include "statslog.h"
#define BPF_FD_JUST_USE_INT
@ -228,6 +222,8 @@ static struct psi_threshold psi_thresholds[VMPRESS_LEVEL_COUNT] = {
};
static android_log_context ctx;
static Reaper reaper;
static int reaper_comm_fd[2];
enum polling_update {
POLLING_DO_NOT_CHANGE,
@ -277,9 +273,9 @@ static struct event_handler_info vmpressure_hinfo[VMPRESS_LEVEL_COUNT];
/*
* 1 ctrl listen socket, 3 ctrl data socket, 3 memory pressure levels,
* 1 lmk events + 1 fd to wait for process death
* 1 lmk events + 1 fd to wait for process death + 1 fd to receive kill failure notifications
*/
#define MAX_EPOLL_EVENTS (1 + MAX_DATA_CONN + VMPRESS_LEVEL_COUNT + 1 + 1)
#define MAX_EPOLL_EVENTS (1 + MAX_DATA_CONN + VMPRESS_LEVEL_COUNT + 1 + 1 + 1)
static int epollfd;
static int maxevents;
@ -2008,42 +2004,6 @@ static struct proc *proc_get_heaviest(int oomadj) {
return maxprocp;
}
static void set_process_group_and_prio(int pid, const std::vector<std::string>& profiles,
int prio) {
DIR* d;
char proc_path[PATH_MAX];
struct dirent* de;
snprintf(proc_path, sizeof(proc_path), "/proc/%d/task", pid);
if (!(d = opendir(proc_path))) {
ALOGW("Failed to open %s; errno=%d: process pid(%d) might have died", proc_path, errno,
pid);
return;
}
while ((de = readdir(d))) {
int t_pid;
if (de->d_name[0] == '.') continue;
t_pid = atoi(de->d_name);
if (!t_pid) {
ALOGW("Failed to get t_pid for '%s' of pid(%d)", de->d_name, pid);
continue;
}
if (setpriority(PRIO_PROCESS, t_pid, prio) && errno != ESRCH) {
ALOGW("Unable to raise priority of killing t_pid (%d): errno=%d", t_pid, errno);
}
if (!SetTaskProfiles(t_pid, profiles, true)) {
ALOGW("Failed to set task_profiles on pid(%d) t_pid(%d)", pid, t_pid);
continue;
}
}
closedir(d);
}
static bool is_kill_pending(void) {
char buf[24];
@ -2114,6 +2074,19 @@ static void kill_done_handler(int data __unused, uint32_t events __unused,
poll_params->update = POLLING_RESUME;
}
static void kill_fail_handler(int data __unused, uint32_t events __unused,
struct polling_params *poll_params) {
int pid;
// Extract pid from the communication pipe. Clearing the pipe this way allows further
// epoll_wait calls to sleep until the next event.
if (TEMP_FAILURE_RETRY(read(reaper_comm_fd[0], &pid, sizeof(pid))) != sizeof(pid)) {
ALOGE("thread communication read failed: %s", strerror(errno));
}
stop_wait_for_proc_kill(false);
poll_params->update = POLLING_RESUME;
}
static void start_wait_for_proc_kill(int pid_or_fd) {
static struct event_handler_info kill_done_hinfo = { 0, kill_done_handler };
struct epoll_event epev;
@ -2149,7 +2122,7 @@ static int kill_one_process(struct proc* procp, int min_oom_score, struct kill_i
int pidfd = procp->pidfd;
uid_t uid = procp->uid;
char *taskname;
int r;
int kill_result;
int result = -1;
struct memory_stat *mem_st;
struct kill_stat kill_st;
@ -2188,29 +2161,21 @@ static int kill_one_process(struct proc* procp, int min_oom_score, struct kill_i
snprintf(desc, sizeof(desc), "lmk,%d,%d,%d,%d,%d", pid, ki ? (int)ki->kill_reason : -1,
procp->oomadj, min_oom_score, ki ? ki->max_thrashing : -1);
trace_kill_start(pid, desc);
/* CAP_KILL required */
if (pidfd < 0) {
start_wait_for_proc_kill(pid);
r = kill(pid, SIGKILL);
} else {
start_wait_for_proc_kill(pidfd);
r = pidfd_send_signal(pidfd, SIGKILL, NULL, 0);
}
start_wait_for_proc_kill(pidfd < 0 ? pid : pidfd);
kill_result = reaper.kill({ pidfd, pid });
trace_kill_end();
if (r) {
if (kill_result) {
stop_wait_for_proc_kill(false);
ALOGE("kill(%d): errno=%d", pid, errno);
/* Delete process record even when we fail to kill so that we don't get stuck on it */
goto out;
}
set_process_group_and_prio(pid, {"CPUSET_SP_FOREGROUND", "SCHED_SP_FOREGROUND"},
ANDROID_PRIORITY_HIGHEST);
last_kill_tm = *tm;
inc_killcnt(procp->oomadj);
@ -3158,6 +3123,63 @@ static void destroy_monitors() {
}
}
static void drop_reaper_comm() {
close(reaper_comm_fd[0]);
close(reaper_comm_fd[1]);
}
static bool setup_reaper_comm() {
if (pipe(reaper_comm_fd)) {
ALOGE("pipe failed: %s", strerror(errno));
return false;
}
// Ensure main thread never blocks on read
int flags = fcntl(reaper_comm_fd[0], F_GETFL);
if (fcntl(reaper_comm_fd[0], F_SETFL, flags | O_NONBLOCK)) {
ALOGE("fcntl failed: %s", strerror(errno));
drop_reaper_comm();
return false;
}
return true;
}
static bool init_reaper() {
if (!reaper.is_reaping_supported()) {
ALOGI("Process reaping is not supported");
return false;
}
if (!setup_reaper_comm()) {
ALOGE("Failed to create thread communication channel");
return false;
}
// Setup epoll handler
struct epoll_event epev;
static struct event_handler_info kill_failed_hinfo = { 0, kill_fail_handler };
epev.events = EPOLLIN;
epev.data.ptr = (void *)&kill_failed_hinfo;
if (epoll_ctl(epollfd, EPOLL_CTL_ADD, reaper_comm_fd[0], &epev)) {
ALOGE("epoll_ctl failed: %s", strerror(errno));
drop_reaper_comm();
return false;
}
if (!reaper.init(reaper_comm_fd[1])) {
ALOGE("Failed to initialize reaper object");
if (epoll_ctl(epollfd, EPOLL_CTL_DEL, reaper_comm_fd[0], &epev)) {
ALOGE("epoll_ctl failed: %s", strerror(errno));
}
drop_reaper_comm();
return false;
}
maxevents++;
return true;
}
static int init(void) {
static struct event_handler_info kernel_poll_hinfo = { 0, kernel_event_handler };
struct reread_data file_data = {
@ -3480,6 +3502,8 @@ static void update_props() {
thrashing_limit_pct * 2));
swap_util_max = clamp(0, 100, GET_LMK_PROPERTY(int32, "swap_util_max", 100));
filecache_min_kb = GET_LMK_PROPERTY(int64, "filecache_min_kb", 0);
reaper.enable_debug(debug_process_killing);
}
int main(int argc, char **argv) {
@ -3521,6 +3545,11 @@ int main(int argc, char **argv) {
}
}
if (init_reaper()) {
ALOGI("Process reaper initialized with %d threads in the pool",
reaper.thread_cnt());
}
mainloop();
}

248
reaper.cpp Normal file
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@ -0,0 +1,248 @@
/*
* Copyright 2021 Google, Inc
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#define LOG_TAG "lowmemorykiller"
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <log/log.h>
#include <signal.h>
#include <string.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <sys/pidfd.h>
#include <sys/resource.h>
#include <sys/sysinfo.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#include <processgroup/processgroup.h>
#include <system/thread_defs.h>
#include "reaper.h"
#define NS_PER_MS (NS_PER_SEC / MS_PER_SEC)
#define THREAD_POOL_SIZE 2
#ifndef __NR_process_mrelease
#define __NR_process_mrelease 448
#endif
static int process_mrelease(int pidfd, unsigned int flags) {
return syscall(__NR_process_mrelease, pidfd, flags);
}
static inline long get_time_diff_ms(struct timespec *from,
struct timespec *to) {
return (to->tv_sec - from->tv_sec) * (long)MS_PER_SEC +
(to->tv_nsec - from->tv_nsec) / (long)NS_PER_MS;
}
static void* reaper_main(void* param) {
Reaper *reaper = static_cast<Reaper*>(param);
struct timespec start_tm, end_tm;
struct Reaper::target_proc target;
pid_t tid = gettid();
// Ensure the thread does not use little cores
if (!SetTaskProfiles(tid, {"CPUSET_SP_FOREGROUND"}, true)) {
ALOGE("Failed to assign cpuset to the reaper thread");
}
for (;;) {
target = reaper->dequeue_request();
if (reaper->debug_enabled()) {
clock_gettime(CLOCK_MONOTONIC_COARSE, &start_tm);
}
if (pidfd_send_signal(target.pidfd, SIGKILL, NULL, 0)) {
// Inform the main thread about failure to kill
reaper->notify_kill_failure(target.pid);
goto done;
}
if (process_mrelease(target.pidfd, 0)) {
ALOGE("process_mrelease %d failed: %s", target.pidfd, strerror(errno));
goto done;
}
if (reaper->debug_enabled()) {
clock_gettime(CLOCK_MONOTONIC_COARSE, &end_tm);
ALOGI("Process %d was reaped in %ldms", target.pid,
get_time_diff_ms(&start_tm, &end_tm));
}
done:
close(target.pidfd);
reaper->request_complete();
}
return NULL;
}
bool Reaper::is_reaping_supported() {
static enum {
UNKNOWN,
SUPPORTED,
UNSUPPORTED
} reap_support = UNKNOWN;
if (reap_support == UNKNOWN) {
if (process_mrelease(-1, 0) && errno == ENOSYS) {
reap_support = UNSUPPORTED;
} else {
reap_support = SUPPORTED;
}
}
return reap_support == SUPPORTED;
}
bool Reaper::init(int comm_fd) {
char name[16];
if (thread_cnt_ > 0) {
// init should not be called multiple times
return false;
}
thread_pool_ = new pthread_t[THREAD_POOL_SIZE];
for (int i = 0; i < THREAD_POOL_SIZE; i++) {
if (pthread_create(&thread_pool_[thread_cnt_], NULL, reaper_main, this)) {
ALOGE("pthread_create failed: %s", strerror(errno));
continue;
}
snprintf(name, sizeof(name), "lmkd_reaper%d", thread_cnt_);
if (pthread_setname_np(thread_pool_[thread_cnt_], name)) {
ALOGW("pthread_setname_np failed: %s", strerror(errno));
}
thread_cnt_++;
}
if (!thread_cnt_) {
delete[] thread_pool_;
return false;
}
queue_.reserve(thread_cnt_);
comm_fd_ = comm_fd;
return true;
}
static void set_process_group_and_prio(int pid, const std::vector<std::string>& profiles,
int prio) {
DIR* d;
char proc_path[PATH_MAX];
struct dirent* de;
snprintf(proc_path, sizeof(proc_path), "/proc/%d/task", pid);
if (!(d = opendir(proc_path))) {
ALOGW("Failed to open %s; errno=%d: process pid(%d) might have died", proc_path, errno,
pid);
return;
}
while ((de = readdir(d))) {
int t_pid;
if (de->d_name[0] == '.') continue;
t_pid = atoi(de->d_name);
if (!t_pid) {
ALOGW("Failed to get t_pid for '%s' of pid(%d)", de->d_name, pid);
continue;
}
if (setpriority(PRIO_PROCESS, t_pid, prio) && errno != ESRCH) {
ALOGW("Unable to raise priority of killing t_pid (%d): errno=%d", t_pid, errno);
}
if (!SetTaskProfiles(t_pid, profiles, true)) {
ALOGW("Failed to set task_profiles on pid(%d) t_pid(%d)", pid, t_pid);
continue;
}
}
closedir(d);
}
bool Reaper::async_kill(const struct target_proc& target) {
if (target.pidfd == -1) {
return false;
}
if (!thread_cnt_) {
return false;
}
mutex_.lock();
if (active_requests_ >= thread_cnt_) {
mutex_.unlock();
return false;
}
active_requests_++;
// Duplicate pidfd instead of reusing the original one to avoid synchronization and refcounting
// when both reaper and main threads are using or closing the pidfd
queue_.push_back({ dup(target.pidfd), target.pid });
// Wake up a reaper thread
cond_.notify_one();
mutex_.unlock();
set_process_group_and_prio(target.pid, {"CPUSET_SP_FOREGROUND", "SCHED_SP_FOREGROUND"},
ANDROID_PRIORITY_HIGHEST);
return true;
}
int Reaper::kill(const struct target_proc& target) {
/* CAP_KILL required */
if (target.pidfd < 0) {
return ::kill(target.pid, SIGKILL);
}
if (async_kill(target)) {
// we assume the kill will be successful and if it fails we will be notified
return 0;
}
return pidfd_send_signal(target.pidfd, SIGKILL, NULL, 0);
}
Reaper::target_proc Reaper::dequeue_request() {
struct target_proc target;
std::unique_lock<std::mutex> lock(mutex_);
while (queue_.empty()) {
cond_.wait(lock);
}
target = queue_.back();
queue_.pop_back();
return target;
}
void Reaper::request_complete() {
std::scoped_lock<std::mutex> lock(mutex_);
active_requests_--;
}
void Reaper::notify_kill_failure(int pid) {
std::scoped_lock<std::mutex> lock(mutex_);
ALOGE("Failed to kill process %d", pid);
if (TEMP_FAILURE_RETRY(write(comm_fd_, &pid, sizeof(pid))) != sizeof(pid)) {
ALOGE("thread communication write failed: %s", strerror(errno));
}
}

59
reaper.h Normal file
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@ -0,0 +1,59 @@
/*
* Copyright 2021 Google, Inc
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include <condition_variable>
#include <mutex>
#include <vector>
class Reaper {
public:
struct target_proc {
int pidfd;
int pid;
};
private:
// mutex_ and cond_ are used to wakeup the reaper thread.
std::mutex mutex_;
std::condition_variable cond_;
// mutex_ protects queue_ and active_requests_ access.
std::vector<struct target_proc> queue_;
int active_requests_;
// write side of the pipe to communicate kill failures with the main thread
int comm_fd_;
int thread_cnt_;
pthread_t* thread_pool_;
bool debug_enabled_;
bool async_kill(const struct target_proc& target);
public:
Reaper() : active_requests_(0), thread_cnt_(0), debug_enabled_(false) {}
static bool is_reaping_supported();
bool init(int comm_fd);
int thread_cnt() const { return thread_cnt_; }
void enable_debug(bool enable) { debug_enabled_ = enable; }
bool debug_enabled() const { return debug_enabled_; }
// return 0 on success or error code returned by the syscall
int kill(const struct target_proc& target);
// below members are used only by reaper_main
target_proc dequeue_request();
void request_complete();
void notify_kill_failure(int pid);
};