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:
Collaboration diagram for tbb::internal::mail_outbox:

Public Member Functions

void 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))
 

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...
 
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 96 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 158 of file mailbox.h.

References __TBB_ASSERT, tbb::internal::NFS_MaxLineSize, and tbb::internal::suppress_unused_warning().

158  {
159  __TBB_ASSERT( sizeof(*this)==NFS_MaxLineSize, NULL );
160  __TBB_ASSERT( !my_first, NULL );
161  __TBB_ASSERT( !my_last, NULL );
162  __TBB_ASSERT( !my_is_idle, NULL );
163  my_last=&my_first;
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
#define __TBB_ASSERT(predicate, comment)
No-op version of __TBB_ASSERT.
Definition: tbb_stddef.h:165
bool my_is_idle
Owner of mailbox is not executing a task, and has drained its own task pool.
Definition: mailbox.h:91
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◆ drain()

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

Drain the mailbox.

Definition at line 168 of file mailbox.h.

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

168  {
169  intptr_t k = 0;
170  // No fences here because other threads have already quit.
171  for( ; task_proxy* t = my_first; ++k ) {
172  my_first = t->next_in_mailbox;
174  }
175  return k;
176  }
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.
proxy_ptr my_first
Pointer to first task_proxy in mailbox, or NULL if box is empty.
Definition: mailbox.h:85
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◆ empty()

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

Return true if mailbox is empty.

Definition at line 150 of file mailbox.h.

References tbb::internal::__TBB_load_relaxed().

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

150  {
151  return __TBB_load_relaxed(my_first) == NULL;
152  }
proxy_ptr my_first
Pointer to first task_proxy in mailbox, or NULL if box is empty.
Definition: mailbox.h:85
T __TBB_load_relaxed(const volatile T &location)
Definition: tbb_machine.h:738
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◆ internal_pop()

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

Definition at line 98 of file mailbox.h.

References __TBB_ASSERT, __TBB_control_consistency_helper, tbb::internal::__TBB_load_relaxed(), tbb::internal::as_atomic(), tbb::internal::task_proxy::next_in_mailbox, tbb::internal::no_isolation, and tbb::internal::atomic_backoff::pause().

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

98  {
99  task_proxy* curr = __TBB_load_relaxed( my_first );
100  if ( !curr )
101  return NULL;
102  task_proxy **prev_ptr = &my_first;
103 #if __TBB_TASK_ISOLATION
104  if ( isolation != no_isolation ) {
105  while ( curr->prefix().isolation != isolation ) {
106  prev_ptr = &curr->next_in_mailbox;
107  curr = curr->next_in_mailbox;
108  if ( !curr )
109  return NULL;
110  }
111  }
112 #endif /* __TBB_TASK_ISOLATION */
113  __TBB_control_consistency_helper(); // on my_first
114  // There is a first item in the mailbox. See if there is a second.
115  if ( task_proxy* second = curr->next_in_mailbox ) {
116  // There are at least two items, so first item can be popped easily.
117  *prev_ptr = second;
118  } else {
119  // There is only one item. Some care is required to pop it.
120  *prev_ptr = NULL;
121  if ( as_atomic( my_last ).compare_and_swap( prev_ptr, &curr->next_in_mailbox ) == &curr->next_in_mailbox ) {
122  // Successfully transitioned mailbox from having one item to having none.
123  __TBB_ASSERT( !curr->next_in_mailbox, NULL );
124  } else {
125  // Some other thread updated my_last but has not filled in first->next_in_mailbox
126  // Wait until first item points to second item.
127  atomic_backoff backoff;
128  while ( !(second = curr->next_in_mailbox) ) backoff.pause();
129  *prev_ptr = second;
130  }
131  }
132  __TBB_ASSERT( curr, NULL );
133  return curr;
134  }
#define __TBB_control_consistency_helper()
Definition: gcc_generic.h:60
const isolation_tag no_isolation
Definition: task.h:133
atomic< T > & as_atomic(T &t)
Definition: atomic.h:572
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
#define __TBB_ASSERT(predicate, comment)
No-op version of __TBB_ASSERT.
Definition: tbb_stddef.h:165
T __TBB_load_relaxed(const volatile T &location)
Definition: tbb_machine.h:738
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◆ push()

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

Push task_proxy onto the mailbox queue of another thread.

Implementation is wait-free.

Definition at line 140 of file mailbox.h.

References __TBB_ASSERT, tbb::internal::__TBB_store_relaxed(), and tbb::internal::task_proxy::next_in_mailbox.

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

140  {
141  __TBB_ASSERT(t, NULL);
142  t->next_in_mailbox = NULL;
143  proxy_ptr * const link = (proxy_ptr *)__TBB_FetchAndStoreW(&my_last,(intptr_t)&t->next_in_mailbox);
144  // No release fence required for the next store, because there are no memory operations
145  // between the previous fully fenced atomic operation and the store.
146  __TBB_store_relaxed(*link, t);
147  }
void __TBB_store_relaxed(volatile T &location, V value)
Definition: tbb_machine.h:742
proxy_ptr *__TBB_atomic my_last
Pointer to pointer that will point to next item in the queue. Never NULL.
Definition: mailbox.h:88
#define __TBB_ASSERT(predicate, comment)
No-op version of __TBB_ASSERT.
Definition: tbb_stddef.h:165
task_proxy *__TBB_atomic proxy_ptr
Definition: mailbox.h:82
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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 179 of file mailbox.h.

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

179  {
180  return my_is_idle;
181  }
bool my_is_idle
Owner of mailbox is not executing a task, and has drained its own task pool.
Definition: mailbox.h:91
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Friends And Related Function Documentation

◆ mail_inbox

friend class mail_inbox
friend

Definition at line 136 of file mailbox.h.


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

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