lmkd: Implement watchdog thread am: af1b0e0627 am: ac20c53b63 am: c871dc1afc

Original change: https://android-review.googlesource.com/c/platform/system/memory/lmkd/+/1894200

Change-Id: I13e24f1b7dfe92359d56344e133843f0f64cec4e

Android.bp

@@ -15,6 +15,7 @@ cc_binary {
     srcs: [
         "lmkd.cpp",
         "reaper.cpp",
+        "watchdog.cpp",
     ],
     shared_libs: [
         "libcutils",

lmkd.cpp

@@ -34,6 +34,8 @@
 #include <time.h>
 #include <unistd.h>
 
+#include <shared_mutex>
+
 #include <cutils/properties.h>
 #include <cutils/sockets.h>
 #include <liblmkd_utils.h>
@@ -46,6 +48,7 @@
 
 #include "reaper.h"
 #include "statslog.h"
+#include "watchdog.h"
 
 #define BPF_FD_JUST_USE_INT
 #include "BpfSyscallWrappers.h"
@@ -161,6 +164,8 @@ static inline void trace_kill_end() {}
 
 #define LMKD_REINIT_PROP "lmkd.reinit"
 
+#define WATCHDOG_TIMEOUT_SEC 2
+
 /* default to old in-kernel interface if no memory pressure events */
 static bool use_inkernel_interface = true;
 static bool has_inkernel_module;
@@ -523,6 +528,11 @@ static struct proc *pidhash[PIDHASH_SZ];
 
 #define ADJTOSLOT(adj) ((adj) + -OOM_SCORE_ADJ_MIN)
 #define ADJTOSLOT_COUNT (ADJTOSLOT(OOM_SCORE_ADJ_MAX) + 1)
+
+// protects procadjslot_list from concurrent access
+static std::shared_mutex adjslot_list_lock;
+// procadjslot_list should be modified only from the main thread while exclusively holding
+// adjslot_list_lock. Readers from non-main threads should hold adjslot_list_lock shared lock.
 static struct adjslot_list procadjslot_list[ADJTOSLOT_COUNT];
 
 #define MAX_DISTINCT_OOM_ADJ 32
@@ -912,13 +922,18 @@ static struct adjslot_list *adjslot_tail(struct adjslot_list *head) {
     return asl == head ? NULL : asl;
 }
 
+// Should be modified only from the main thread.
 static void proc_slot(struct proc *procp) {
     int adjslot = ADJTOSLOT(procp->oomadj);
+    std::scoped_lock lock(adjslot_list_lock);
 
     adjslot_insert(&procadjslot_list[adjslot], &procp->asl);
 }
 
+// Should be modified only from the main thread.
 static void proc_unslot(struct proc *procp) {
+    std::scoped_lock lock(adjslot_list_lock);
+
     adjslot_remove(&procp->asl);
 }
 
@@ -1955,16 +1970,24 @@ static void killinfo_log(struct proc* procp, int min_oom_score, int rss_kb,
 
     /* log meminfo fields */
     for (int field_idx = 0; field_idx < MI_FIELD_COUNT; field_idx++) {
-        android_log_write_int32(ctx, (int32_t)min(mi->arr[field_idx] * page_k, INT32_MAX));
+        android_log_write_int32(ctx, mi ? (int32_t)min(mi->arr[field_idx] * page_k, INT32_MAX): 0);
     }
 
     /* log lmkd wakeup information */
-    android_log_write_int32(ctx, (int32_t)get_time_diff_ms(&wi->last_event_tm, tm));
-    android_log_write_int32(ctx, (int32_t)get_time_diff_ms(&wi->prev_wakeup_tm, tm));
-    android_log_write_int32(ctx, wi->wakeups_since_event);
-    android_log_write_int32(ctx, wi->skipped_wakeups);
+    if (wi) {
+        android_log_write_int32(ctx, (int32_t)get_time_diff_ms(&wi->last_event_tm, tm));
+        android_log_write_int32(ctx, (int32_t)get_time_diff_ms(&wi->prev_wakeup_tm, tm));
+        android_log_write_int32(ctx, wi->wakeups_since_event);
+        android_log_write_int32(ctx, wi->skipped_wakeups);
+    } else {
+        android_log_write_int32(ctx, 0);
+        android_log_write_int32(ctx, 0);
+        android_log_write_int32(ctx, 0);
+        android_log_write_int32(ctx, 0);
+    }
+
     android_log_write_int32(ctx, (int32_t)min(swap_kb, INT32_MAX));
-    android_log_write_int32(ctx, (int32_t)mi->field.total_gpu_kb);
+    android_log_write_int32(ctx, mi ? (int32_t)mi->field.total_gpu_kb : 0);
     if (ki) {
         android_log_write_int32(ctx, ki->thrashing);
         android_log_write_int32(ctx, ki->max_thrashing);
@@ -1977,10 +2000,33 @@ static void killinfo_log(struct proc* procp, int min_oom_score, int rss_kb,
     android_log_reset(ctx);
 }
 
-static struct proc *proc_adj_lru(int oomadj) {
+// Note: returned entry is only an anchor and does not hold a valid process info.
+// When called from a non-main thread, adjslot_list_lock read lock should be taken.
+static struct proc *proc_adj_head(int oomadj) {
+    return (struct proc *)&procadjslot_list[ADJTOSLOT(oomadj)];
+}
+
+// When called from a non-main thread, adjslot_list_lock read lock should be taken.
+static struct proc *proc_adj_tail(int oomadj) {
     return (struct proc *)adjslot_tail(&procadjslot_list[ADJTOSLOT(oomadj)]);
 }
 
+// When called from a non-main thread, adjslot_list_lock read lock should be taken.
+static struct proc *proc_adj_prev(int oomadj, int pid) {
+    struct adjslot_list *head = &procadjslot_list[ADJTOSLOT(oomadj)];
+    struct adjslot_list *curr = adjslot_tail(&procadjslot_list[ADJTOSLOT(oomadj)]);
+
+    while (curr != head) {
+        if (((struct proc *)curr)->pid == pid) {
+            return (struct proc *)curr->prev;
+        }
+        curr = curr->prev;
+    }
+
+    return NULL;
+}
+
+// When called from a non-main thread, adjslot_list_lock read lock should be taken.
 static struct proc *proc_get_heaviest(int oomadj) {
     struct adjslot_list *head = &procadjslot_list[ADJTOSLOT(oomadj)];
     struct adjslot_list *curr = head->next;
@@ -2004,6 +2050,55 @@ static struct proc *proc_get_heaviest(int oomadj) {
     return maxprocp;
 }
 
+static bool find_victim(int oom_score, int prev_pid, struct proc &target_proc) {
+    struct proc *procp;
+    std::shared_lock lock(adjslot_list_lock);
+
+    if (!prev_pid) {
+        procp = proc_adj_tail(oom_score);
+    } else {
+        procp = proc_adj_prev(oom_score, prev_pid);
+        if (!procp) {
+            // pid was removed, restart at the tail
+            procp = proc_adj_tail(oom_score);
+        }
+    }
+
+    // the list is empty at this oom_score or we looped through it
+    if (!procp || procp == proc_adj_head(oom_score)) {
+        return false;
+    }
+
+    // make a copy because original might be destroyed after adjslot_list_lock is released
+    target_proc = *procp;
+
+    return true;
+}
+
+static void watchdog_callback() {
+    int prev_pid = 0;
+
+    ALOGW("lmkd watchdog timed out!");
+    for (int oom_score = OOM_SCORE_ADJ_MAX; oom_score >= 0;) {
+        struct proc target;
+
+        if (!find_victim(oom_score, prev_pid, target)) {
+            oom_score--;
+            prev_pid = 0;
+            continue;
+        }
+
+        if (reaper.kill({ target.pidfd, target.pid }, true) == 0) {
+            ALOGW("lmkd watchdog killed process %d, oom_score_adj %d", target.pid, oom_score);
+            killinfo_log(&target, 0, 0, 0, NULL, NULL, NULL, NULL);
+            break;
+        }
+        prev_pid = target.pid;
+    }
+}
+
+static Watchdog watchdog(WATCHDOG_TIMEOUT_SEC, watchdog_callback);
+
 static bool is_kill_pending(void) {
     char buf[24];
 
@@ -2165,7 +2260,7 @@ static int kill_one_process(struct proc* procp, int min_oom_score, struct kill_i
     trace_kill_start(pid, desc);
 
     start_wait_for_proc_kill(pidfd < 0 ? pid : pidfd);
-    kill_result = reaper.kill({ pidfd, pid });
+    kill_result = reaper.kill({ pidfd, pid }, false);
 
     trace_kill_end();
 
@@ -2241,7 +2336,7 @@ static int find_and_kill_process(int min_score_adj, struct kill_info *ki, union
 
         while (true) {
             procp = choose_heaviest_task ?
-                proc_get_heaviest(i) : proc_adj_lru(i);
+                proc_get_heaviest(i) : proc_adj_tail(i);
 
             if (!procp)
                 break;
@@ -3297,6 +3392,7 @@ static void call_handler(struct event_handler_info* handler_info,
                          struct polling_params *poll_params, uint32_t events) {
     struct timespec curr_tm;
 
+    watchdog.start();
     poll_params->update = POLLING_DO_NOT_CHANGE;
     handler_info->handler(handler_info->data, events, poll_params);
     clock_gettime(CLOCK_MONOTONIC_COARSE, &curr_tm);
@@ -3328,6 +3424,7 @@ static void call_handler(struct event_handler_info* handler_info,
         }
         break;
     }
+    watchdog.stop();
 }
 
 static void mainloop(void) {
@@ -3409,7 +3506,9 @@ static void mainloop(void) {
             if ((evt->events & EPOLLHUP) && evt->data.ptr) {
                 ALOGI("lmkd data connection dropped");
                 handler_info = (struct event_handler_info*)evt->data.ptr;
+                watchdog.start();
                 ctrl_data_close(handler_info->data);
+                watchdog.stop();
             }
         }
 
@@ -3550,6 +3649,10 @@ int main(int argc, char **argv) {
                 reaper.thread_cnt());
         }
 
+        if (!watchdog.init()) {
+            ALOGE("Failed to initialize the watchdog");
+        }
+
         mainloop();
     }
 

reaper.cpp

@@ -206,18 +206,23 @@ bool Reaper::async_kill(const struct target_proc& target) {
     return true;
 }
 
-int Reaper::kill(const struct target_proc& target) {
+int Reaper::kill(const struct target_proc& target, bool synchronous) {
     /* CAP_KILL required */
     if (target.pidfd < 0) {
         return ::kill(target.pid, SIGKILL);
     }
 
-    if (async_kill(target)) {
+    if (!synchronous && 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);
+    int result = pidfd_send_signal(target.pidfd, SIGKILL, NULL, 0);
+    if (result) {
+        return result;
+    }
+
+    return is_reaping_supported() ? process_mrelease(target.pidfd, 0) : 0;
 }
 
 Reaper::target_proc Reaper::dequeue_request() {

reaper.h

@@ -51,7 +51,7 @@ public:
     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);
+    int kill(const struct target_proc& target, bool synchronous);
     // below members are used only by reaper_main
     target_proc dequeue_request();
     void request_complete();

watchdog.cpp

@@ -0,0 +1,123 @@
+/*
+ *  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 <errno.h>
+#include <log/log.h>
+#include <string.h>
+
+#include <processgroup/processgroup.h>
+
+#include "watchdog.h"
+
+static void* watchdog_main(void* param) {
+    Watchdog *watchdog = static_cast<Watchdog*>(param);
+    sigset_t sigset;
+    int signum;
+
+    // Ensure the thread does not use little cores
+    if (!SetTaskProfiles(gettid(), {"CPUSET_SP_FOREGROUND"}, true)) {
+        ALOGE("Failed to assign cpuset to the watchdog thread");
+    }
+
+    if (!watchdog->create_timer(sigset)) {
+        ALOGE("Watchdog timer creation failed!");
+        return NULL;
+    }
+
+    while (true) {
+        if (sigwait(&sigset, &signum) == -1) {
+            ALOGE("sigwait failed: %s", strerror(errno));
+        }
+
+        watchdog->bite();
+    }
+
+    return NULL;
+}
+
+bool Watchdog::init() {
+    pthread_t thread;
+
+    if (pthread_create(&thread, NULL, watchdog_main, this)) {
+        ALOGE("pthread_create failed: %s", strerror(errno));
+        return false;
+    }
+    if (pthread_setname_np(thread, "lmkd_watchdog")) {
+        ALOGW("pthread_setname_np failed: %s", strerror(errno));
+    }
+
+    return true;
+}
+
+bool Watchdog::start() {
+    // Start the timer and keep it active until it's disarmed
+    struct itimerspec new_timer;
+
+    if (!timer_created_) {
+        return false;
+    }
+
+    new_timer.it_value.tv_sec = timeout_;
+    new_timer.it_value.tv_nsec = 0;
+    new_timer.it_interval.tv_sec = timeout_;
+    new_timer.it_interval.tv_nsec = 0;
+
+    if (timer_settime(timer_, 0, &new_timer, NULL)) {
+        ALOGE("timer_settime failed: %s", strerror(errno));
+        return false;
+    }
+
+    return true;
+}
+
+bool Watchdog::stop() {
+    struct itimerspec new_timer = {};
+
+    if (!timer_created_) {
+        return false;
+    }
+
+    if (timer_settime(timer_, 0, &new_timer, NULL)) {
+        ALOGE("timer_settime failed: %s", strerror(errno));
+        return false;
+    }
+
+    return true;
+}
+
+bool Watchdog::create_timer(sigset_t &sigset) {
+    struct sigevent sevent;
+
+    sigemptyset(&sigset);
+    sigaddset(&sigset, SIGALRM);
+    if (sigprocmask(SIG_BLOCK, &sigset, NULL)) {
+        ALOGE("sigprocmask failed: %s", strerror(errno));
+        return false;
+    }
+
+    sevent.sigev_notify = SIGEV_THREAD_ID;
+    sevent.sigev_notify_thread_id = gettid();
+    sevent.sigev_signo = SIGALRM;
+    if (timer_create(CLOCK_MONOTONIC, &sevent, &timer_)) {
+        ALOGE("timer_create failed: %s", strerror(errno));
+        return false;
+    }
+
+    timer_created_ = true;
+    return true;
+}

watchdog.h

@@ -0,0 +1,39 @@
+/*
+ *  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 <atomic>
+#include <signal.h>
+#include <time.h>
+
+class Watchdog {
+private:
+    int timeout_;
+    timer_t timer_;
+    std::atomic<bool> timer_created_;
+    void (*callback_)();
+public:
+    Watchdog(int timeout, void (*callback)()) :
+        timeout_(timeout), timer_created_(false), callback_(callback) {}
+
+    bool init();
+    bool start();
+    bool stop();
+    // used by the watchdog_main
+    bool create_timer(sigset_t &sigset);
+    void bite() const { if (callback_) callback_(); }
+};