[vlc-devel] [PATCH 01/11] os2: thread: implement missing threading functions
Rémi Denis-Courmont
remi at remlab.net
Mon Jan 25 11:53:35 UTC 2021
Hi,
Where is the atomic-wait algorithm from? It's entirely clear to me if it's correct.
Le 20 janvier 2021 11:49:23 GMT+02:00, KO Myung-Hun <komh78 at gmail.com> a écrit :
>---
> src/os2/thread.c | 351 ++++++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 302 insertions(+), 49 deletions(-)
>
>diff --git a/src/os2/thread.c b/src/os2/thread.c
>index 0d7bc9e79f..1c4774f04c 100644
>--- a/src/os2/thread.c
>+++ b/src/os2/thread.c
>@@ -39,6 +39,9 @@
> #include <errno.h>
> #include <time.h>
>
>+#include <stdalign.h>
>+#include <stdatomic.h>
>+
> #include <sys/types.h>
> #ifdef HAVE_SYS_SOCKET_H
> #include <sys/socket.h>
>@@ -51,6 +54,11 @@
>
> #include <sys/stat.h>
>
>+/* Static mutex and condition variable */
>+static vlc_mutex_t super_mutex;
>+static vlc_cond_t super_variable;
>+
>+/* Threads */
> static vlc_threadvar_t thread_key;
>
> struct vlc_thread
>@@ -61,11 +69,17 @@ struct vlc_thread
> int cancel_sock;
>
> bool killable;
>- bool killed;
>+ atomic_bool killed;
> vlc_cleanup_t *cleaners;
>
> void *(*entry) (void *);
> void *data;
>+
>+ struct
>+ {
>+ atomic_uint *addr;
>+ HMTX lock;
>+ } wait;
> };
>
> static void vlc_cancel_self (PVOID dummy);
>@@ -129,40 +143,6 @@ static ULONG vlc_Sleep (ULONG ulTimeout)
> return ( rc != ERROR_TIMEOUT ) ? rc : 0;
> }
>
>-static vlc_mutex_t super_mutex;
>-static vlc_cond_t super_variable;
>-
>-int _CRT_init(void);
>-void _CRT_term(void);
>-
>-unsigned long _System _DLL_InitTerm(unsigned long, unsigned long);
>-
>-unsigned long _System _DLL_InitTerm(unsigned long hmod, unsigned long
>flag)
>-{
>- VLC_UNUSED (hmod);
>-
>- switch (flag)
>- {
>- case 0 : /* Initialization */
>- if(_CRT_init() == -1)
>- return 0;
>-
>- vlc_mutex_init (&super_mutex);
>- vlc_cond_init (&super_variable);
>- vlc_threadvar_create (&thread_key, NULL);
>-
>- return 1;
>-
>- case 1 : /* Termination */
>- vlc_threadvar_delete (&thread_key);
>-
>- _CRT_term();
>-
>- return 1;
>- }
>-
>- return 0; /* Failed */
>-}
>
> /*** Thread-specific variables (TLS) ***/
> struct vlc_threadvar
>@@ -232,6 +212,197 @@ void *vlc_threadvar_get (vlc_threadvar_t key)
> return ( void * )*key->id;
> }
>
>+static struct wait_bucket
>+{
>+ HMTX lock;
>+ HEV wait;
>+ unsigned waiters;
>+} wait_buckets[ 32 ];
>+
>+static void wait_bucket_init( void )
>+{
>+ for( size_t i = 0; i < ARRAY_SIZE( wait_buckets ); i++ )
>+ {
>+ struct wait_bucket *bucket = wait_buckets + i;
>+
>+ DosCreateMutexSem( NULL, &bucket->lock, 0L, FALSE );
>+ DosCreateEventSem( NULL, &bucket->wait, 0L, FALSE );
>+ }
>+}
>+
>+static void wait_bucket_destroy( void )
>+{
>+ for( size_t i = 0; i < ARRAY_SIZE( wait_buckets ); i++ )
>+ {
>+ struct wait_bucket *bucket = wait_buckets + i;
>+
>+ DosCloseMutexSem( bucket->lock );
>+ DosCloseEventSem( bucket->wait );
>+ }
>+}
>+
>+static struct wait_bucket *wait_bucket_get( atomic_uint *addr )
>+{
>+ uintptr_t u = ( uintptr_t )addr;
>+ size_t idx = ( u / alignof ( *addr )) % ARRAY_SIZE( wait_buckets
>);
>+
>+ return &wait_buckets[ idx ];
>+}
>+
>+static struct wait_bucket *wait_bucket_enter( atomic_uint *addr )
>+{
>+ struct wait_bucket *bucket = wait_bucket_get(addr);
>+
>+ DosRequestMutexSem( bucket->lock, SEM_INDEFINITE_WAIT );
>+ bucket->waiters++;
>+
>+ return bucket;
>+}
>+
>+static void wait_bucket_leave( void *data )
>+{
>+ struct wait_bucket *bucket = data;
>+
>+ bucket->waiters--;
>+ DosReleaseMutexSem( bucket->lock );
>+}
>+
>+void vlc_atomic_wait( void *addr, unsigned value )
>+{
>+ atomic_uint *futex = addr;
>+ struct wait_bucket *bucket = wait_bucket_enter( futex );
>+
>+ vlc_cleanup_push( wait_bucket_leave, bucket );
>+
>+ if( value == atomic_load_explicit( futex, memory_order_relaxed ))
>+ {
>+ ULONG count;
>+
>+ DosReleaseMutexSem( bucket->lock );
>+ vlc_WaitForSingleObject( bucket->wait, SEM_INDEFINITE_WAIT );
>+ DosResetEventSem( bucket->wait, &count );
>+ DosRequestMutexSem( bucket->lock, SEM_INDEFINITE_WAIT );
>+ }
>+ else
>+ vlc_testcancel();
>+
>+ wait_bucket_leave( bucket );
>+ vlc_cleanup_pop();
>+}
>+
>+int vlc_atomic_timedwait(void *addr, unsigned value, vlc_tick_t
>deadline)
>+{
>+ atomic_uint *futex = addr;
>+ struct wait_bucket *bucket = wait_bucket_enter( futex );
>+
>+ ULONG rc = 0;
>+
>+ vlc_cleanup_push( wait_bucket_leave, bucket );
>+
>+ if( value == atomic_load_explicit( futex, memory_order_relaxed ))
>+ {
>+ vlc_tick_t delay;
>+
>+ DosReleaseMutexSem( bucket->lock );
>+
>+ do
>+ {
>+ ULONG ms;
>+ ULONG count;
>+
>+ delay = deadline - vlc_tick_now();
>+
>+ if( delay < 0 )
>+ ms = 0;
>+ else if( delay >= VLC_TICK_FROM_MS( LONG_MAX ))
>+ ms = LONG_MAX;
>+ else
>+ ms = MS_FROM_VLC_TICK( delay );
>+
>+ rc = vlc_WaitForSingleObject( bucket->wait, ms );
>+ if( rc == 0 )
>+ {
>+ DosResetEventSem( bucket->wait, &count );
>+ break;
>+ }
>+ } while( delay > 0 );
>+
>+ DosRequestMutexSem( bucket->lock, SEM_INDEFINITE_WAIT );
>+ }
>+ else
>+ vlc_testcancel();
>+
>+ wait_bucket_leave( bucket );
>+ vlc_cleanup_pop();
>+
>+ return rc == 0 ? 0 : ETIMEDOUT;
>+}
>+
>+int vlc_atomic_timedwait_daytime(void *addr, unsigned value, time_t
>deadline)
>+{
>+ atomic_uint *futex = addr;
>+ struct wait_bucket *bucket = wait_bucket_enter( futex );
>+
>+ ULONG rc = 0;
>+
>+ vlc_cleanup_push( wait_bucket_leave, bucket );
>+
>+ if( value == atomic_load_explicit( futex, memory_order_relaxed ))
>+ {
>+ vlc_tick_t delay;
>+
>+ DosReleaseMutexSem( bucket->lock );
>+
>+ do
>+ {
>+ ULONG ms;
>+ ULONG count;
>+
>+ delay = deadline - time( NULL );
>+
>+ if( delay < 0 )
>+ ms = 0;
>+ else if( delay >= ( LONG_MAX / 1000 ))
>+ ms = LONG_MAX;
>+ else
>+ ms = delay * 1000;
>+
>+ rc = vlc_WaitForSingleObject( bucket->wait, ms );
>+ if( rc == 0 )
>+ {
>+ DosResetEventSem( bucket->wait, &count );
>+ break;
>+ }
>+ } while( delay > 0 );
>+
>+ DosRequestMutexSem( bucket->lock, SEM_INDEFINITE_WAIT );
>+ }
>+ else
>+ vlc_testcancel();
>+
>+ wait_bucket_leave( bucket );
>+ vlc_cleanup_pop();
>+
>+ return rc == 0 ? 0 : ETIMEDOUT;
>+}
>+
>+void vlc_atomic_notify_one(void *addr)
>+{
>+ vlc_atomic_notify_all(addr);
>+}
>+
>+void vlc_atomic_notify_all(void *addr)
>+{
>+ struct wait_bucket *bucket = wait_bucket_get(addr);
>+
>+ DosRequestMutexSem( bucket->lock, SEM_INDEFINITE_WAIT );
>+
>+ if( bucket->waiters > 0 )
>+ DosPostEventSem( bucket->wait );
>+
>+ DosReleaseMutexSem( bucket->lock);
>+}
>+
>
> /*** Threads ***/
> void vlc_threads_setup (libvlc_int_t *p_libvlc)
>@@ -280,8 +451,9 @@ int vlc_clone (vlc_thread_t *p_handle, void
>*(*entry) (void *),
> th->entry = entry;
> th->data = data;
> th->killable = false; /* not until vlc_entry() ! */
>- th->killed = false;
>+ atomic_init (&th->killed, false);
> th->cleaners = NULL;
>+ th->wait.addr = NULL;
>
> if( DosCreateEventSem (NULL, &th->cancel_event, 0, FALSE))
> goto error;
>@@ -292,6 +464,9 @@ int vlc_clone (vlc_thread_t *p_handle, void
>*(*entry) (void *),
> if( th->cancel_sock < 0 )
> goto error;
>
>+ if( DosCreateMutexSem (NULL, &th->wait.lock, 0, FALSE))
>+ goto error;
>+
> th->tid = _beginthread (vlc_entry, NULL, 1024 * 1024, th);
> if((int)th->tid == -1)
> goto error;
>@@ -308,6 +483,7 @@ int vlc_clone (vlc_thread_t *p_handle, void
>*(*entry) (void *),
> return 0;
>
> error:
>+ DosCloseMutexSem (th->wait.lock);
> soclose (th->cancel_sock);
> DosCloseEventSem (th->cancel_event);
> DosCloseEventSem (th->done_event);
>@@ -334,6 +510,8 @@ void vlc_join (vlc_thread_t th, void **result)
>
> soclose( th->cancel_sock );
>
>+ DosCloseMutexSem( th->wait.lock );
>+
> free( th );
> }
>
>@@ -360,13 +538,23 @@ static void vlc_cancel_self (PVOID self)
> struct vlc_thread *th = self;
>
> if (likely(th != NULL))
>- th->killed = true;
>+ atomic_store_explicit (&th->killed, true,
>memory_order_relaxed);
> }
>
>-void vlc_cancel (vlc_thread_t thread_id)
>+void vlc_cancel (vlc_thread_t th)
> {
>- DosPostEventSem( thread_id->cancel_event );
>- so_cancel( thread_id->cancel_sock );
>+ atomic_store_explicit( &th->killed, true, memory_order_relaxed );
>+
>+ DosRequestMutexSem( th->wait.lock, SEM_INDEFINITE_WAIT );
>+ if( th->wait.addr != NULL )
>+ {
>+ atomic_fetch_or_explicit( th->wait.addr, 1,
>memory_order_relaxed );
>+ vlc_atomic_notify_all( th->wait.addr );
>+ }
>+ DosReleaseMutexSem( th->wait.lock );
>+
>+ DosPostEventSem( th->cancel_event );
>+ so_cancel( th->cancel_sock );
> }
>
> int vlc_savecancel (void)
>@@ -400,21 +588,26 @@ void vlc_testcancel (void)
> if (th == NULL)
> return; /* Main thread - cannot be cancelled anyway */
>
>+ if (!th->killable)
>+ return;
>+
> /* This check is needed for the case that vlc_cancel() is followed by
> * vlc_testcancel() without any cancellation point */
> if( DosWaitEventSem( th->cancel_event, 0 ) == NO_ERROR )
> vlc_cancel_self( th );
>
>- if (th->killable && th->killed)
>- {
>- for (vlc_cleanup_t *p = th->cleaners; p != NULL; p = p->next)
>- p->proc (p->data);
>+ if( !atomic_load_explicit( &th->killed, memory_order_relaxed ))
>+ return;
>
>- DosPostEventSem( th->done_event );
>- th->data = NULL; /* TODO: special value? */
>- vlc_thread_cleanup (th);
>- _endthread();
>- }
>+ th->killable = true; /* Do not re-enter cancellation cleanup */
>+
>+ for (vlc_cleanup_t *p = th->cleaners; p != NULL; p = p->next)
>+ p->proc (p->data);
>+
>+ DosPostEventSem( th->done_event );
>+ th->data = NULL; /* TODO: special value? */
>+ vlc_thread_cleanup (th);
>+ _endthread();
> }
>
> void vlc_control_cancel (vlc_cleanup_t *cleaner)
>@@ -439,6 +632,30 @@ void vlc_control_cancel (vlc_cleanup_t *cleaner)
> }
> }
>
>+void vlc_cancel_addr_set( atomic_uint *addr )
>+{
>+ struct vlc_thread *th = vlc_threadvar_get( thread_key );
>+ if( th == NULL )
>+ return; /* Main thread - cannot be cancelled anyway */
>+
>+ DosRequestMutexSem( th->wait.lock, SEM_INDEFINITE_WAIT );
>+ assert( th->wait.addr == NULL );
>+ th->wait.addr = addr;
>+ DosReleaseMutexSem( th->wait.lock );
>+}
>+
>+void vlc_cancel_addr_clear( atomic_uint *addr )
>+{
>+ struct vlc_thread *th = vlc_threadvar_get( thread_key );
>+ if( th == NULL )
>+ return; /* Main thread - cannot be cancelled anyway */
>+
>+ DosRequestMutexSem( th->wait.lock, SEM_INDEFINITE_WAIT );
>+ assert( th->wait.addr == addr );
>+ th->wait.addr = NULL;
>+ DosReleaseMutexSem( th->wait.lock );
>+}
>+
>static int vlc_select( int nfds, fd_set *rdset, fd_set *wrset, fd_set
>*exset,
> struct timeval *timeout )
> {
>@@ -705,3 +922,39 @@ unsigned vlc_GetCPUCount (void)
>
> return numprocs;
> }
>+
>+int _CRT_init(void);
>+void _CRT_term(void);
>+
>+unsigned long _System _DLL_InitTerm(unsigned long, unsigned long);
>+
>+unsigned long _System _DLL_InitTerm(unsigned long hmod, unsigned long
>flag)
>+{
>+ VLC_UNUSED (hmod);
>+
>+ switch (flag)
>+ {
>+ case 0 : /* Initialization */
>+ if(_CRT_init() == -1)
>+ return 0;
>+
>+ wait_bucket_init();
>+
>+ vlc_mutex_init (&super_mutex);
>+ vlc_cond_init (&super_variable);
>+ vlc_threadvar_create (&thread_key, NULL);
>+
>+ return 1;
>+
>+ case 1 : /* Termination */
>+ vlc_threadvar_delete (&thread_key);
>+
>+ wait_bucket_destroy();
>+
>+ _CRT_term();
>+
>+ return 1;
>+ }
>+
>+ return 0; /* Failed */
>+}
>--
>2.22.0
>
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