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vdr/thread.h

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/*
* thread.h: A simple thread base class
*
* See the main source file 'vdr.c' for copyright information and
* how to reach the author.
*
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* $Id: thread.h 4.6 2020/09/16 13:48:33 kls Exp $
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*/
#ifndef __THREAD_H
#define __THREAD_H
#include <pthread.h>
#include <stdio.h>
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#include <sys/types.h>
typedef pid_t tThreadId;
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class cCondWait {
private:
pthread_mutex_t mutex;
pthread_cond_t cond;
bool signaled;
public:
cCondWait(void);
~cCondWait();
static void SleepMs(int TimeoutMs);
///< Creates a cCondWait object and uses it to sleep for TimeoutMs
///< milliseconds, immediately giving up the calling thread's time
///< slice and thus avoiding a "busy wait".
///< In order to avoid a possible busy wait, TimeoutMs will be automatically
///< limited to values >2.
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bool Wait(int TimeoutMs = 0);
///< Waits at most TimeoutMs milliseconds for a call to Signal(), or
///< forever if TimeoutMs is 0.
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///< Returns true if Signal() has been called, false if the given
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///< timeout has expired.
void Signal(void);
///< Signals a caller of Wait() that the condition it is waiting for is met.
};
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class cMutex;
class cCondVar {
private:
pthread_cond_t cond;
public:
cCondVar(void);
~cCondVar();
void Wait(cMutex &Mutex);
bool TimedWait(cMutex &Mutex, int TimeoutMs);
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void Broadcast(void);
};
class cRwLock {
private:
pthread_rwlock_t rwlock;
int locked;
tThreadId writeLockThreadId;
public:
cRwLock(bool PreferWriter = false);
~cRwLock();
bool Lock(bool Write, int TimeoutMs = 0);
void Unlock(void);
};
class cMutex {
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friend class cCondVar;
private:
pthread_mutex_t mutex;
int locked;
public:
cMutex(void);
~cMutex();
void Lock(void);
void Unlock(void);
};
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class cThread {
friend class cThreadLock;
private:
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bool active;
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bool running;
pthread_t childTid;
tThreadId childThreadId;
cMutex mutex;
char *description;
bool lowPriority;
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static tThreadId mainThreadId;
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static void *StartThread(cThread *Thread);
protected:
void SetPriority(int Priority);
void SetIOPriority(int Priority);
void Lock(void) { mutex.Lock(); }
void Unlock(void) { mutex.Unlock(); }
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virtual void Action(void) = 0;
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///< A derived cThread class must implement the code it wants to
///< execute as a separate thread in this function. If this is
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///< a loop, it must check Running() repeatedly to see whether
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///< it's time to stop.
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bool Running(void) { return running; }
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///< Returns false if a derived cThread object shall leave its Action()
///< function.
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void Cancel(int WaitSeconds = 0);
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///< Cancels the thread by first setting 'running' to false, so that
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///< the Action() loop can finish in an orderly fashion and then waiting
///< up to WaitSeconds seconds for the thread to actually end. If the
///< thread doesn't end by itself, it is killed.
///< If WaitSeconds is -1, only 'running' is set to false and Cancel()
///< returns immediately, without killing the thread.
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public:
cThread(const char *Description = NULL, bool LowPriority = false);
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///< Creates a new thread.
///< If Description is present, a log file entry will be made when
///< the thread starts and stops (see SetDescription()).
///< The Start() function must be called to actually start the thread.
///< LowPriority can be set to true to make this thread run at a lower
///< priority.
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virtual ~cThread();
void SetDescription(const char *Description, ...) __attribute__ ((format (printf, 2, 3)));
///< Sets the description of this thread, which will be used when logging
///< starting or stopping of the thread. Make sure any important information
///< is within the first 15 characters of Description, because only these
///< may be displayed in thread listings (like 'htop', for instance).
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bool Start(void);
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///< Actually starts the thread.
///< If the thread is already running, nothing happens.
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bool Active(void);
///< Checks whether the thread is still alive.
static tThreadId ThreadId(void);
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static tThreadId IsMainThread(void) { return ThreadId() == mainThreadId; }
static void SetMainThreadId(void);
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};
// cMutexLock can be used to easily set a lock on mutex and make absolutely
// sure that it will be unlocked when the block will be left. Several locks can
// be stacked, so a function that makes many calls to another function which uses
// cMutexLock may itself use a cMutexLock to make one longer lock instead of many
// short ones.
class cMutexLock {
private:
cMutex *mutex;
bool locked;
public:
cMutexLock(cMutex *Mutex = NULL);
~cMutexLock();
bool Lock(cMutex *Mutex);
};
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// cThreadLock can be used to easily set a lock in a thread and make absolutely
// sure that it will be unlocked when the block will be left. Several locks can
// be stacked, so a function that makes many calls to another function which uses
// cThreadLock may itself use a cThreadLock to make one longer lock instead of many
// short ones.
class cThreadLock {
private:
cThread *thread;
bool locked;
public:
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cThreadLock(cThread *Thread = NULL);
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~cThreadLock();
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bool Lock(cThread *Thread);
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};
#define LOCK_THREAD cThreadLock ThreadLock(this)
class cStateKey;
class cStateLock {
friend class cStateKey;
private:
enum { emDisabled = 0, emArmed, emEnabled };
const char *name;
tThreadId threadId;
cRwLock rwLock;
int state;
int explicitModify;
cStateKey *syncStateKey;
void Unlock(cStateKey &StateKey, bool IncState = true);
///< Releases a lock that has been obtained by a previous call to Lock()
///< with the given StateKey. If this was a write-lock, and IncState is true,
///< the state of the lock will be incremented. In any case, the (new) state
///< of the lock will be copied to the StateKey's state.
public:
cStateLock(const char *Name = NULL);
bool Lock(cStateKey &StateKey, bool Write = false, int TimeoutMs = 0);
///< Tries to get a lock and returns true if successful.
///< If TimoutMs is not 0, it waits for the given number of milliseconds
///< and returns false if no lock has been obtained within that time.
///< Otherwise it waits indefinitely for the lock. The given StateKey
///< will store which lock it has been used with, and will use that
///< information when its Remove() function is called.
///< There are two possible locks, one only for read access, and one
///< for reading and writing:
///<
///< If Write is false (i.e. a read-lock is requested), the lock's state
///< is compared to the given StateKey's state, and true is returned if
///< they differ.
///< If true is returned, the read-lock is still in place and the
///< protected data structures can be safely accessed (in read-only mode!).
///< Once the necessary operations have been performed, the lock must
///< be released by a call to the StateKey's Remove() function.
///< If false is returned, the state has not changed since the last check,
///< and the read-lock has been released. In that case the protected
///< data structures have not changed since the last call, so no action
///< is required. Note that if TimeoutMs is used with read-locks, Lock()
///< might return false even if the states of lock and key differ, just
///< because it was unable to obtain the lock within the given time.
///< You can call cStateKey::TimedOut() to detect this.
///<
///< If Write is true (i.e. a write-lock is requested), the states of the
///< lock and the given StateKey don't matter, it will always try to obtain
///< a write lock.
void SetSyncStateKey(cStateKey &StateKey);
///< Sets the given StateKey to be synchronized to the state of this lock.
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///< The caller must currently hold a write lock on this lock, with a cStateKey
///< that is different from the given StateKey. If, when removing the key that
///< is holding the write lock, the StateKey's current state is the same as that
///< of the lock, it will be increased together with the lock's state.
void SetExplicitModify(void);
///< If you have obtained a write lock on this lock, and you don't want its
///< state to be automatically incremented when the lock is released, a call to
///< this function will disable this, and you can explicitly call SetModified()
///< to increment the state.
void SetModified(void);
///< Sets this lock to have its state incremented when the current write lock
///< state key is removed. Must have called SetExplicitModify() before calling
///< this function.
};
class cStateKey {
friend class cStateLock;
private:
cStateLock *stateLock;
bool write;
int state;
bool timedOut;
public:
cStateKey(bool IgnoreFirst = false);
///< Sets up a new state key. If IgnoreFirst is true, the first use
///< of this key with a lock will not return true if the lock's state
///< hasn't explicitly changed.
~cStateKey();
void Reset(void);
///< Resets the state of this key, so that the next call to a lock's
///< Lock() function with this key will return true, even if the
///< lock's state hasn't changed.
void Remove(bool IncState = true);
///< Removes this key from the lock it was previously used with.
///< If this key was used to obtain a write lock, the state of the lock will
///< be incremented and copied to this key. You can set IncState to false
///< to prevent this.
bool StateChanged(void);
///< Returns true if this key is used for obtaining a write lock, and the
///< lock's state differs from that of the key. When used with a read lock,
///< it always returns true, because otherwise the lock wouldn't have been
///< obtained in the first place.
bool InLock(void) { return stateLock; }
///< Returns true if this key is currently in a lock.
bool TimedOut(void) const { return timedOut; }
///< Returns true if the last lock attempt this key was used with failed due
///< to a timeout.
};
class cIoThrottle {
private:
static cMutex mutex;
static int count;
bool active;
public:
cIoThrottle(void);
~cIoThrottle();
void Activate(void);
///< Activates the global I/O throttling mechanism.
///< This function may be called any number of times, but only
///< the first call after an inactive state will have an effect.
void Release(void);
///< Releases the global I/O throttling mechanism.
///< This function may be called any number of times, but only
///< the first call after an active state will have an effect.
bool Active(void) { return active; }
///< Returns true if this I/O throttling object is currently active.
static bool Engaged(void);
///< Returns true if any I/O throttling object is currently active.
};
// cPipe implements a pipe that closes all unnecessary file descriptors in
// the child process.
class cPipe {
private:
pid_t pid;
FILE *f;
public:
cPipe(void);
~cPipe();
operator FILE* () { return f; }
bool Open(const char *Command, const char *Mode);
int Close(void);
};
// cBackTrace can be used for debugging.
class cStringList;
class cString;
class cBackTrace {
public:
static cString Demangle(char *s);
///< Demangles the function name in the given string and returns the converted
///< version of s. s must be one of the strings returned by a call to
///< BackTrace() or GetCaller().
///< Note that this function works on the given string by inserting '\0'
///< characters to separate the individual parts. Therefore the string
///< will be modified upon return.
static void BackTrace(cStringList &StringList, int Level = 0, bool Mangled = false);
///< Produces a backtrace and stores it in the given StringList.
///< If Level is given, only calls up to the given value are listed.
///< If Mangled is true, the raw backtrace will be returned and you can use
///< Demangle() to make the function names readable.
static void BackTrace(FILE *f = NULL, int Level = 0, bool Mangled = false);
///< Produces a backtrace beginning at the given Level, and
///< writes it to the given file. If no file is given, the backtrace is
///< written to the logfile. If Mangled is true, the raw backtrace will
///< be printed/logged.
static cString GetCaller(int Level = 0, bool Mangled = false);
///< Returns the caller at the given Level (or the immediate caller,
///< if Level is 0).
///< If Mangled is true, the raw backtrace will be returned and you can use
///< Demangle() to make the function name readable.
};
// SystemExec() implements a 'system()' call that closes all unnecessary file
// descriptors in the child process.
// With Detached=true, calls command in background and in a separate session,
// with stdin connected to /dev/null.
int SystemExec(const char *Command, bool Detached = false);
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#endif //__THREAD_H