7e2cb84e9c
If the signal to dump a thread is never delivered, then it's
possible for a deadlock. The signal handler is responsible for
unlocking and deleting the ThreadEntry created for the pid/tid
combination. This means if the signal is lost, the ThreadEntry
gets stuck locked and never deleted. If a second attempt to get
a backtrace of this thread occurs, there is a deadlock.
Also, decrease the timeout from 10 seconds to 5 seconds. The original
10 seconds was because the unwind was actually done in the signal
handler. Now the signal handler does nothing but copy the ucontext
structure and let the caller do the unwind.
Bug: 21086132
(cherry picked from commit 2d09171758)
Change-Id: I414c500eb08983a5017caf3fce4f499465575a9d
71 lines
1.7 KiB
C++
71 lines
1.7 KiB
C++
/*
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* Copyright (C) 2013 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef _LIBBACKTRACE_THREAD_ENTRY_H
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#define _LIBBACKTRACE_THREAD_ENTRY_H
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#include <pthread.h>
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#include <sys/types.h>
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#include <ucontext.h>
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class ThreadEntry {
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public:
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static ThreadEntry* Get(pid_t pid, pid_t tid, bool create = true);
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static void Remove(ThreadEntry* entry);
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void Wake();
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bool Wait(int);
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void CopyUcontextFromSigcontext(void*);
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inline void Lock() {
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pthread_mutex_lock(&mutex_);
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// Always reset the wait value since this could be the first or nth
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// time this entry is locked.
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wait_value_ = 0;
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}
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inline void Unlock() {
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pthread_mutex_unlock(&mutex_);
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}
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inline ucontext_t* GetUcontext() { return &ucontext_; }
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private:
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ThreadEntry(pid_t pid, pid_t tid);
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~ThreadEntry();
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bool Match(pid_t chk_pid, pid_t chk_tid) { return (chk_pid == pid_ && chk_tid == tid_); }
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pid_t pid_;
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pid_t tid_;
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int ref_count_;
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pthread_mutex_t mutex_;
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pthread_mutex_t wait_mutex_;
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pthread_cond_t wait_cond_;
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int wait_value_;
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ThreadEntry* next_;
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ThreadEntry* prev_;
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ucontext_t ucontext_;
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static ThreadEntry* list_;
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static pthread_mutex_t list_mutex_;
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};
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#endif // _LIBBACKTRACE_THREAD_ENTRY_H
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