Intel(R) Threading Building Blocks Doxygen Documentation version 4.2.3
tbb::internal::mail_outbox Class Reference

Class representing where mail is put. More...

#include <mailbox.h>

Inheritance diagram for tbb::internal::mail_outbox:
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Public Member Functions

bool push (task_proxy *t)
 Push task_proxy onto the mailbox queue of another thread. More...
 
bool empty ()
 Return true if mailbox is empty. More...
 
void construct ()
 Construct *this as a mailbox from zeroed memory. More...
 
intptr_t drain ()
 Drain the mailbox. More...
 
bool recipient_is_idle ()
 True if thread that owns this mailbox is looking for work. More...
 

Private Member Functions

task_proxyinternal_pop (__TBB_ISOLATION_EXPR(isolation_tag isolation))
 

Static Private Attributes

static const int mailbox_task_limit = 32
 

Friends

class mail_inbox
 

Additional Inherited Members

- Private Types inherited from tbb::internal::unpadded_mail_outbox
typedef task_proxy *__TBB_atomic proxy_ptr
 
- Private Attributes inherited from tbb::internal::padded_base< unpadded_mail_outbox, NFS_MaxLineSize, sizeof(unpadded_mail_outbox) % NFS_MaxLineSize >
char pad [S - R]
 
- Private Attributes inherited from tbb::internal::unpadded_mail_outbox
proxy_ptr my_first
 Pointer to first task_proxy in mailbox, or NULL if box is empty. More...
 
proxy_ptr *__TBB_atomic my_last
 Pointer to pointer that will point to next item in the queue. Never NULL. More...
 
tbb::atomic< intmy_task_count
 Approximate number of tasks in mailbox to prevent an unlimited grow when the owner is not available. More...
 
bool my_is_idle
 Owner of mailbox is not executing a task, and has drained its own task pool. More...
 

Detailed Description

Class representing where mail is put.

Padded to occupy a cache line.

Definition at line 99 of file mailbox.h.

Member Function Documentation

◆ construct()

void tbb::internal::mail_outbox::construct ( )
inline

Construct *this as a mailbox from zeroed memory.

Raise assertion if *this is not previously zeroed, or sizeof(this) is wrong. This method is provided instead of a full constructor since we know the object will be constructed in zeroed memory.

Definition at line 169 of file mailbox.h.

169 {
170 __TBB_ASSERT( sizeof(*this)==NFS_MaxLineSize, NULL );
171 __TBB_ASSERT( !my_first, NULL );
172 __TBB_ASSERT( !my_last, NULL );
173 __TBB_ASSERT( !my_is_idle, NULL );
176 }
#define __TBB_ASSERT(predicate, comment)
No-op version of __TBB_ASSERT.
Definition: tbb_stddef.h:165
const size_t NFS_MaxLineSize
Compile-time constant that is upper bound on cache line/sector size.
Definition: tbb_stddef.h:216
void suppress_unused_warning(const T1 &)
Utility template function to prevent "unused" warnings by various compilers.
Definition: tbb_stddef.h:398
proxy_ptr my_first
Pointer to first task_proxy in mailbox, or NULL if box is empty.
Definition: mailbox.h:85
proxy_ptr *__TBB_atomic my_last
Pointer to pointer that will point to next item in the queue. Never NULL.
Definition: mailbox.h:88
bool my_is_idle
Owner of mailbox is not executing a task, and has drained its own task pool.
Definition: mailbox.h:94

References __TBB_ASSERT, tbb::internal::unpadded_mail_outbox::my_first, tbb::internal::unpadded_mail_outbox::my_is_idle, tbb::internal::unpadded_mail_outbox::my_last, tbb::internal::NFS_MaxLineSize, tbb::internal::padded_base< unpadded_mail_outbox, NFS_MaxLineSize, sizeof(unpadded_mail_outbox) % NFS_MaxLineSize >::pad, and tbb::internal::suppress_unused_warning().

Referenced by tbb::internal::arena::arena().

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◆ drain()

intptr_t tbb::internal::mail_outbox::drain ( )
inline

Drain the mailbox.

Definition at line 179 of file mailbox.h.

179 {
180 intptr_t k = 0;
181 // No fences here because other threads have already quit.
182 for( ; task_proxy* t = my_first; ++k ) {
183 my_first = t->next_in_mailbox;
185 }
186 return k;
187 }
void __TBB_EXPORTED_FUNC NFS_Free(void *)
Free memory allocated by NFS_Allocate.
const size_t task_prefix_reservation_size
Number of bytes reserved for a task prefix.

References tbb::internal::unpadded_mail_outbox::my_first, tbb::internal::task_proxy::next_in_mailbox, tbb::internal::NFS_Free(), and tbb::internal::task_prefix_reservation_size.

Referenced by tbb::internal::arena::free_arena().

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◆ empty()

bool tbb::internal::mail_outbox::empty ( )
inline

Return true if mailbox is empty.

Definition at line 161 of file mailbox.h.

161 {
162 return __TBB_load_relaxed(my_first) == NULL;
163 }
T __TBB_load_relaxed(const volatile T &location)
Definition: tbb_machine.h:735

References tbb::internal::__TBB_load_relaxed(), and tbb::internal::unpadded_mail_outbox::my_first.

Referenced by tbb::internal::mail_inbox::empty().

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◆ internal_pop()

task_proxy * tbb::internal::mail_outbox::internal_pop ( __TBB_ISOLATION_EXPR(isolation_tag isolation)  )
inlineprivate

Definition at line 102 of file mailbox.h.

102 {
103 task_proxy* curr = __TBB_load_relaxed( my_first );
104 if ( !curr )
105 return NULL;
106 task_proxy **prev_ptr = &my_first;
107#if __TBB_TASK_ISOLATION
108 if ( isolation != no_isolation ) {
109 while ( curr->prefix().isolation != isolation ) {
110 prev_ptr = &curr->next_in_mailbox;
111 curr = curr->next_in_mailbox;
112 if ( !curr )
113 return NULL;
114 }
115 }
116#endif /* __TBB_TASK_ISOLATION */
117 __TBB_control_consistency_helper(); // on my_first
118 // There is a first item in the mailbox. See if there is a second.
119 if ( task_proxy* second = curr->next_in_mailbox ) {
120 // There are at least two items, so first item can be popped easily.
121 *prev_ptr = second;
122 } else {
123 // There is only one item. Some care is required to pop it.
124 *prev_ptr = NULL;
125 if ( as_atomic( my_last ).compare_and_swap( prev_ptr, &curr->next_in_mailbox ) == &curr->next_in_mailbox ) {
126 // Successfully transitioned mailbox from having one item to having none.
127 __TBB_ASSERT( !curr->next_in_mailbox, NULL );
128 } else {
129 // Some other thread updated my_last but has not filled in first->next_in_mailbox
130 // Wait until first item points to second item.
131 atomic_backoff backoff;
132 while ( !(second = curr->next_in_mailbox) ) backoff.pause();
133 *prev_ptr = second;
134 }
135 }
137 __TBB_ASSERT( my_task_count >= 0, NULL );
138 __TBB_ASSERT( curr, NULL );
139 return curr;
140 }
#define __TBB_control_consistency_helper()
Definition: gcc_generic.h:60
atomic< T > & as_atomic(T &t)
Definition: atomic.h:572
const isolation_tag no_isolation
Definition: task.h:144
tbb::atomic< int > my_task_count
Approximate number of tasks in mailbox to prevent an unlimited grow when the owner is not available.
Definition: mailbox.h:91

References __TBB_ASSERT, __TBB_control_consistency_helper, tbb::internal::__TBB_load_relaxed(), tbb::internal::as_atomic(), tbb::internal::task_prefix::isolation, tbb::internal::unpadded_mail_outbox::my_first, tbb::internal::unpadded_mail_outbox::my_last, tbb::internal::unpadded_mail_outbox::my_task_count, tbb::internal::task_proxy::next_in_mailbox, tbb::internal::no_isolation, tbb::internal::atomic_backoff::pause(), and tbb::task::prefix().

Referenced by tbb::internal::mail_inbox::pop().

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◆ push()

bool tbb::internal::mail_outbox::push ( task_proxy t)
inline

Push task_proxy onto the mailbox queue of another thread.

Implementation is wait-free. Returns false if there are too many tasks.

Definition at line 147 of file mailbox.h.

147 {
149 return false;
151 __TBB_ASSERT(t, NULL);
152 t->next_in_mailbox = NULL;
153 proxy_ptr * const link = (proxy_ptr *)__TBB_FetchAndStoreW(&my_last,(intptr_t)&t->next_in_mailbox);
154 // No release fence required for the next store, because there are no memory operations
155 // between the previous fully fenced atomic operation and the store.
156 __TBB_store_relaxed(*link, t);
157 return true;
158 }
void __TBB_store_relaxed(volatile T &location, V value)
Definition: tbb_machine.h:739
task_proxy *__TBB_atomic proxy_ptr
Definition: mailbox.h:82
static const int mailbox_task_limit
Definition: mailbox.h:100

References __TBB_ASSERT, tbb::internal::__TBB_store_relaxed(), mailbox_task_limit, tbb::internal::unpadded_mail_outbox::my_last, tbb::internal::unpadded_mail_outbox::my_task_count, and tbb::internal::task_proxy::next_in_mailbox.

Referenced by tbb::internal::generic_scheduler::prepare_for_spawning().

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◆ recipient_is_idle()

bool tbb::internal::mail_outbox::recipient_is_idle ( )
inline

True if thread that owns this mailbox is looking for work.

Definition at line 190 of file mailbox.h.

190 {
191 return my_is_idle;
192 }

References tbb::internal::unpadded_mail_outbox::my_is_idle.

Referenced by tbb::internal::generic_scheduler::steal_task_from().

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Friends And Related Function Documentation

◆ mail_inbox

friend class mail_inbox
friend

Definition at line 142 of file mailbox.h.

Member Data Documentation

◆ mailbox_task_limit

const int tbb::internal::mail_outbox::mailbox_task_limit = 32
staticprivate

Definition at line 100 of file mailbox.h.

Referenced by push().


The documentation for this class was generated from the following file:

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