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      1 /*
      2  * Copyright (C) 2015 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include <pthread.h>
     18 #include <stdint.h>
     19 #include <string.h>
     20 #include <sys/types.h>
     21 #include <time.h>
     22 #include <ucontext.h>
     23 
     24 #include "BacktraceAsyncSafeLog.h"
     25 #include "ThreadEntry.h"
     26 
     27 // Initialize static member variables.
     28 ThreadEntry* ThreadEntry::list_ = nullptr;
     29 pthread_mutex_t ThreadEntry::list_mutex_ = PTHREAD_MUTEX_INITIALIZER;
     30 
     31 // Assumes that ThreadEntry::list_mutex_ has already been locked before
     32 // creating a ThreadEntry object.
     33 ThreadEntry::ThreadEntry(pid_t pid, pid_t tid)
     34     : pid_(pid), tid_(tid), ref_count_(1), mutex_(PTHREAD_MUTEX_INITIALIZER),
     35       wait_mutex_(PTHREAD_MUTEX_INITIALIZER), wait_value_(0),
     36       next_(ThreadEntry::list_), prev_(nullptr) {
     37   pthread_condattr_t attr;
     38   pthread_condattr_init(&attr);
     39   pthread_condattr_setclock(&attr, CLOCK_MONOTONIC);
     40   pthread_cond_init(&wait_cond_, &attr);
     41 
     42   // Add ourselves to the list.
     43   if (ThreadEntry::list_) {
     44     ThreadEntry::list_->prev_ = this;
     45   }
     46   ThreadEntry::list_ = this;
     47 }
     48 
     49 ThreadEntry* ThreadEntry::Get(pid_t pid, pid_t tid, bool create) {
     50   pthread_mutex_lock(&ThreadEntry::list_mutex_);
     51   ThreadEntry* entry = list_;
     52   while (entry != nullptr) {
     53     if (entry->Match(pid, tid)) {
     54       break;
     55     }
     56     entry = entry->next_;
     57   }
     58 
     59   if (!entry) {
     60     if (create) {
     61       entry = new ThreadEntry(pid, tid);
     62     }
     63   } else {
     64     entry->ref_count_++;
     65   }
     66   pthread_mutex_unlock(&ThreadEntry::list_mutex_);
     67 
     68   return entry;
     69 }
     70 
     71 void ThreadEntry::Remove(ThreadEntry* entry) {
     72   entry->Unlock();
     73 
     74   pthread_mutex_lock(&ThreadEntry::list_mutex_);
     75   if (--entry->ref_count_ == 0) {
     76     delete entry;
     77   }
     78   pthread_mutex_unlock(&ThreadEntry::list_mutex_);
     79 }
     80 
     81 // Assumes that ThreadEntry::list_mutex_ has already been locked before
     82 // deleting a ThreadEntry object.
     83 ThreadEntry::~ThreadEntry() {
     84   if (list_ == this) {
     85     list_ = next_;
     86   } else {
     87     if (next_) {
     88       next_->prev_ = prev_;
     89     }
     90     prev_->next_ = next_;
     91   }
     92 
     93   next_ = nullptr;
     94   prev_ = nullptr;
     95 
     96   pthread_cond_destroy(&wait_cond_);
     97 }
     98 
     99 bool ThreadEntry::Wait(int value) {
    100   timespec ts;
    101   clock_gettime(CLOCK_MONOTONIC, &ts);
    102   ts.tv_sec += 5;
    103 
    104   bool wait_completed = true;
    105   pthread_mutex_lock(&wait_mutex_);
    106   while (wait_value_ != value) {
    107     int ret = pthread_cond_timedwait(&wait_cond_, &wait_mutex_, &ts);
    108     if (ret != 0) {
    109       BACK_ASYNC_SAFE_LOGW("pthread_cond_timedwait for value %d failed: %s", value, strerror(ret));
    110       wait_completed = false;
    111       break;
    112     }
    113   }
    114   pthread_mutex_unlock(&wait_mutex_);
    115 
    116   return wait_completed;
    117 }
    118 
    119 void ThreadEntry::Wake() {
    120   pthread_mutex_lock(&wait_mutex_);
    121   wait_value_++;
    122   pthread_mutex_unlock(&wait_mutex_);
    123 
    124   pthread_cond_signal(&wait_cond_);
    125 }
    126 
    127 void ThreadEntry::CopyUcontextFromSigcontext(void* sigcontext) {
    128   ucontext_t* ucontext = reinterpret_cast<ucontext_t*>(sigcontext);
    129   // The only thing the unwinder cares about is the mcontext data.
    130   memcpy(&ucontext_.uc_mcontext, &ucontext->uc_mcontext, sizeof(ucontext->uc_mcontext));
    131 }
    132