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Cleanup pthread usage

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No functional change.
This commit is contained in:
Andrea Mazzoleni 2016-02-06 15:08:11 +01:00
parent 104f8b065e
commit 29ed19174f
3 changed files with 58 additions and 48 deletions
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98
cmdline/io.c
View file

@ -19,6 +19,13 @@
#include "io.h"
/**
* At now pthread is required.
*/
#if !HAVE_PTHREAD
#error Pthread library is required for InputOutput!
#endif
/**
* Implementation note about conditional variables.
*
@ -37,6 +44,39 @@
* Calling pthread_cond_signal without locking mutex
* http://stackoverflow.com/questions/4544234/calling-pthread-cond-signal-without-locking-mutex/4544494#4544494
*/
static void pthread_cond_signal_and_unlock(pthread_cond_t* cond, pthread_mutex_t* mutex)
{
#ifndef CHECKER
/* without the thread checker unlock before signaling, */
/* this reduces the number of context switches */
pthread_mutex_unlock(mutex);
#endif
pthread_cond_signal(cond);
#ifdef CHECKER
/* with the thread checker unlock after signaling */
/* to make explicit the condition and mutex relation */
pthread_mutex_unlock(mutex);
#endif
}
static void pthread_cond_broadcast_and_unlock(pthread_cond_t* cond, pthread_mutex_t* mutex)
{
#ifndef CHECKER
/* without the thread checker unlock before signaling, */
/* this reduces the number of context switches */
pthread_mutex_unlock(mutex);
#endif
pthread_cond_broadcast(cond);
#ifdef CHECKER
/* with the thread checker unlock after signaling */
/* to make explicit the condition and mutex relation */
pthread_mutex_unlock(mutex);
#endif
}
void io_init(struct snapraid_io* io, struct snapraid_state* state,
unsigned io_cache, unsigned buffer_max,
@ -299,20 +339,13 @@ static struct snapraid_task* io_reader_step(struct snapraid_worker* worker)
worker->index = next_index;
task = &worker->task_map[worker->index];
#ifndef CHECKER
/* without the thread checker unlock before signaling, */
/* this reduces the number of context switches */
pthread_mutex_unlock(&io->mutex);
#endif
/* if the just completed task is at this index */
if (done_index == waiting_index)
if (done_index == waiting_index) {
/* notify the IO that a new read is complete */
pthread_cond_signal(&io->read_done);
#ifdef CHECKER
pthread_mutex_unlock(&io->mutex);
#endif
pthread_cond_signal_and_unlock(&io->read_done, &io->mutex);
} else {
pthread_mutex_unlock(&io->mutex);
}
/* return the new task */
return task;
@ -361,20 +394,13 @@ static struct snapraid_task* io_writer_step(struct snapraid_worker* worker, int
worker->index = next_index;
task = &worker->task_map[worker->index];
#ifndef CHECKER
/* without the thread checker unlock before signaling, */
/* this reduces the number of context switches */
pthread_mutex_unlock(&io->mutex);
#endif
/* if the just completed task is at this index */
if (done_index == waiting_index)
if (done_index == waiting_index) {
/* notify the IO that a new write is complete */
pthread_cond_signal(&io->write_done);
#ifdef CHECKER
pthread_mutex_unlock(&io->mutex);
#endif
pthread_cond_signal_and_unlock(&io->write_done, &io->mutex);
} else {
pthread_mutex_unlock(&io->mutex);
}
/* return the new task */
return task;
@ -428,18 +454,8 @@ block_off_t io_read_next(struct snapraid_io* io, void*** buffer)
/* set the buffer to use */
*buffer = io->buffer_map[io->reader_index];
#ifndef CHECKER
/* without the thread checker unlock before signaling, */
/* this reduces the number of context switches */
pthread_mutex_unlock(&io->mutex);
#endif
/* signal all the workers that there is a new pending task */
pthread_cond_broadcast(&io->read_sched);
#ifdef CHECKER
pthread_mutex_unlock(&io->mutex);
#endif
pthread_cond_broadcast_and_unlock(&io->read_sched, &io->mutex);
return blockcur_caller;
}
@ -478,18 +494,8 @@ void io_write_next(struct snapraid_io* io, block_off_t blockcur, int skip, int*
/* set the index to be used for the next write */
io->writer_index = (io->writer_index + 1) % io->io_max;
#ifndef CHECKER
/* without the thread checker unlock before signaling, */
/* this reduces the number of context switches */
pthread_mutex_unlock(&io->mutex);
#endif
/* signal all the workers that there is a new pending task */
pthread_cond_broadcast(&io->write_sched);
#ifdef CHECKER
pthread_mutex_unlock(&io->mutex);
#endif
pthread_cond_broadcast_and_unlock(&io->write_sched, &io->mutex);
}
void io_refresh(struct snapraid_io* io)

6
cmdline/io.h
View file

@ -87,7 +87,9 @@ struct snapraid_task {
* from a specific disk.
*/
struct snapraid_worker {
pthread_t thread;
#if HAVE_PTHREAD
pthread_t thread; /**< Thread context for the worker. */
#endif
struct snapraid_io* io; /**< Parent pointer. */
@ -141,6 +143,7 @@ struct snapraid_io {
*/
unsigned io_max;
#if HAVE_PTHREAD
/**
* Mutex used to protect the synchronization
* between the io and the workers.
@ -182,6 +185,7 @@ struct snapraid_io {
* The IO signals this condition when new writes are scheduled.
*/
pthread_cond_t write_sched;
#endif
/**
* Base position for workers.

2
cmdline/portable.h
View file

@ -232,7 +232,7 @@
/**
* Enable thread use.
*/
#if HAVE_PTHREAD_H && HAVE_PTHREAD_CREATE
#if HAVE_PTHREAD_CREATE
#define HAVE_PTHREAD 1
#endif