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authorLasse Collin <lasse.collin@tukaani.org>2011-04-10 21:23:21 +0300
committerLasse Collin <lasse.collin@tukaani.org>2011-04-10 21:23:21 +0300
commit9f0a806aef7ea79718e3f1f2baf3564295229a27 (patch)
tree7d06008086bddd7a6c99a5c085e5ce5da44d87fa /src
parentliblzma: Make lzma_stream_encoder_init() static. (diff)
downloadxz-9f0a806aef7ea79718e3f1f2baf3564295229a27.tar.xz
Revise mythread.h.
This adds: - mythread_sync() macro to create synchronized blocks - mythread_cond structure and related functions and macros for condition variables with timed waiting using a relative timeout - mythread_create() to create a thread with all signals blocked Some of these wouldn't need to be inline functions, but I'll keep them this way for now for simplicity. For timed waiting on a condition variable, librt is now required on some systems to use clock_gettime(). configure.ac was updated to handle this.
Diffstat (limited to 'src')
-rw-r--r--src/common/mythread.h200
1 files changed, 180 insertions, 20 deletions
diff --git a/src/common/mythread.h b/src/common/mythread.h
index 476c2fc9..39641408 100644
--- a/src/common/mythread.h
+++ b/src/common/mythread.h
@@ -1,7 +1,7 @@
///////////////////////////////////////////////////////////////////////////////
//
/// \file mythread.h
-/// \brief Wrappers for threads
+/// \brief Some threading related helper macros and functions
//
// Author: Lasse Collin
//
@@ -14,29 +14,189 @@
#ifdef HAVE_PTHREAD
-# include <pthread.h>
-# define mythread_once(func) \
- do { \
- static pthread_once_t once_ = PTHREAD_ONCE_INIT; \
- pthread_once(&once_, &func); \
- } while (0)
+////////////////////
+// Using pthreads //
+////////////////////
-# define mythread_sigmask(how, set, oset) \
- pthread_sigmask(how, set, oset)
+#include <pthread.h>
+#include <signal.h>
+#include <time.h>
+#include <unistd.h>
+
+
+/// \brief Set the process signal mask
+///
+/// If threads are disabled, sigprocmask() is used instead
+/// of pthread_sigmask().
+#define mythread_sigmask(how, set, oset) \
+ pthread_sigmask(how, set, oset)
+
+
+/// \brief Call the given function once
+///
+/// If threads are disabled, a thread-unsafe version is used.
+#define mythread_once(func) \
+do { \
+ static pthread_once_t once_ = PTHREAD_ONCE_INIT; \
+ pthread_once(&once_, &func); \
+} while (0)
+
+
+/// \brief Lock a mutex for a duration of a block
+///
+/// Perform pthread_mutex_lock(&mutex) in the beginning of a block
+/// and pthread_mutex_unlock(&mutex) at the end of the block. "break"
+/// may be used to unlock the mutex and jump out of the block.
+/// mythread_sync blocks may be nested.
+///
+/// Example:
+///
+/// mythread_sync(mutex) {
+/// foo();
+/// if (some_error)
+/// break; // Skips bar()
+/// bar();
+/// }
+///
+/// At least GCC optimizes the loops completely away so it doesn't slow
+/// things down at all compared to plain pthread_mutex_lock(&mutex)
+/// and pthread_mutex_unlock(&mutex) calls.
+///
+#define mythread_sync(mutex) mythread_sync_helper(mutex, __LINE__)
+#define mythread_sync_helper(mutex, line) \
+ for (unsigned int mythread_i_ ## line = 0; \
+ mythread_i_ ## line \
+ ? (pthread_mutex_unlock(&(mutex)), 0) \
+ : (pthread_mutex_lock(&(mutex)), 1); \
+ mythread_i_ ## line = 1) \
+ for (unsigned int mythread_j_ ## line = 0; \
+ !mythread_j_ ## line; \
+ mythread_j_ ## line = 1)
+
+
+typedef struct {
+ /// Condition variable
+ pthread_cond_t cond;
+
+ /// Clock ID (CLOCK_REALTIME or CLOCK_MONOTONIC) associated with
+ /// the condition variable
+ clockid_t clk_id;
+
+} mythread_cond;
+
+
+/// \brief Initialize a condition variable to use CLOCK_MONOTONIC
+///
+/// Using CLOCK_MONOTONIC instead of the default CLOCK_REALTIME makes the
+/// timeout in pthread_cond_timedwait() work correctly also if system time
+/// is suddenly changed. Unfortunately CLOCK_MONOTONIC isn't available
+/// everywhere while the default CLOCK_REALTIME is, so the default is
+/// used if CLOCK_MONOTONIC isn't available.
+static inline int
+mythread_cond_init(mythread_cond *mycond)
+{
+#if defined(_POSIX_CLOCK_SELECTION) && defined(_POSIX_MONOTONIC_CLOCK)
+ struct timespec ts;
+ pthread_condattr_t condattr;
+
+ // POSIX doesn't seem to *require* that pthread_condattr_setclock()
+ // will fail if given an unsupported clock ID. Test that
+ // CLOCK_MONOTONIC really is supported using clock_gettime().
+ if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0
+ && pthread_condattr_init(&condattr) == 0) {
+ int ret = pthread_condattr_setclock(
+ &condattr, CLOCK_MONOTONIC);
+ if (ret == 0)
+ ret = pthread_cond_init(&mycond->cond, &condattr);
+
+ pthread_condattr_destroy(&condattr);
+
+ if (ret == 0) {
+ mycond->clk_id = CLOCK_MONOTONIC;
+ return 0;
+ }
+ }
+
+ // If anything above fails, fall back to the default CLOCK_REALTIME.
+#endif
+
+ mycond->clk_id = CLOCK_REALTIME;
+ return pthread_cond_init(&mycond->cond, NULL);
+}
+
+
+/// \brief Convert relative time to absolute time for use with timed wait
+///
+/// The current time of the clock associated with the condition variable
+/// is added to the relative time in *ts.
+static inline void
+mythread_cond_abstime(const mythread_cond *mycond, struct timespec *ts)
+{
+ struct timespec now;
+ clock_gettime(mycond->clk_id, &now);
+
+ ts->tv_sec += now.tv_sec;
+ ts->tv_nsec += now.tv_nsec;
+
+ // tv_nsec must stay in the range [0, 999_999_999].
+ if (ts->tv_nsec >= 1000000000L) {
+ ts->tv_nsec -= 1000000000L;
+ ++ts->tv_sec;
+ }
+
+ return;
+}
+
+
+#define mythread_cond_wait(mycondptr, mutexptr) \
+ pthread_cond_wait(&(mycondptr)->cond, mutexptr)
+
+#define mythread_cond_timedwait(mycondptr, mutexptr, abstimeptr) \
+ pthread_cond_timedwait(&(mycondptr)->cond, mutexptr, abstimeptr)
+
+#define mythread_cond_signal(mycondptr) \
+ pthread_cond_signal(&(mycondptr)->cond)
+
+#define mythread_cond_broadcast(mycondptr) \
+ pthread_cond_broadcast(&(mycondptr)->cond)
+
+#define mythread_cond_destroy(mycondptr) \
+ pthread_cond_destroy(&(mycondptr)->cond)
+
+
+/// \brief Create a thread with all signals blocked
+static inline int
+mythread_create(pthread_t *thread, void *(*func)(void *arg), void *arg)
+{
+ sigset_t old;
+ sigset_t all;
+ sigfillset(&all);
+
+ pthread_sigmask(SIG_SETMASK, &all, &old);
+ const int ret = pthread_create(thread, NULL, func, arg);
+ pthread_sigmask(SIG_SETMASK, &old, NULL);
+
+ return ret;
+}
#else
-# define mythread_once(func) \
- do { \
- static bool once_ = false; \
- if (!once_) { \
- func(); \
- once_ = true; \
- } \
- } while (0)
-
-# define mythread_sigmask(how, set, oset) \
- sigprocmask(how, set, oset)
+//////////////////
+// No threading //
+//////////////////
+
+#define mythread_sigmask(how, set, oset) \
+ sigprocmask(how, set, oset)
+
+
+#define mythread_once(func) \
+do { \
+ static bool once_ = false; \
+ if (!once_) { \
+ func(); \
+ once_ = true; \
+ } \
+} while (0)
#endif