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task: concurrency cleanups

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Update thread_local task state pointers while locked.  This avoids
potential concurrent access of the pointers while making copies of them.

Verify that the queue is really empty after splicing lists, and the
current consumer is really gone after swapping the empty one.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>
This commit is contained in:
Zygo Blaxell 2021-11-16 00:39:51 -05:00
parent 5e346beb2d
commit 0103a04ca0
1 changed files with 6 additions and 4 deletions
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10
lib/task.cc
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@ -212,6 +212,7 @@ namespace crucible {
TaskMasterState::push_front(tq_one); TaskMasterState::push_front(tq_one);
} }
} }
assert(queue.empty());
} }
TaskState::~TaskState() TaskState::~TaskState()
@ -292,23 +293,23 @@ namespace crucible {
--m_run_count; --m_run_count;
m_is_running = true; m_is_running = true;
} }
TaskStatePtr this_task = shared_from_this();
swap(this_task, tl_current_task);
lock.unlock(); lock.unlock();
char buf[24] = { 0 }; char buf[24] = { 0 };
DIE_IF_MINUS_ERRNO(pthread_getname_np(pthread_self(), buf, sizeof(buf))); DIE_IF_MINUS_ERRNO(pthread_getname_np(pthread_self(), buf, sizeof(buf)));
DIE_IF_MINUS_ERRNO(pthread_setname_np(pthread_self(), m_title.c_str())); DIE_IF_MINUS_ERRNO(pthread_setname_np(pthread_self(), m_title.c_str()));
TaskStatePtr this_task = shared_from_this();
swap(this_task, tl_current_task);
catch_all([&]() { catch_all([&]() {
m_exec_fn(); m_exec_fn();
}); });
swap(this_task, tl_current_task);
pthread_setname_np(pthread_self(), buf); pthread_setname_np(pthread_self(), buf);
lock.lock(); lock.lock();
swap(this_task, tl_current_task);
m_is_running = false; m_is_running = false;
// Splice task post_exec queue at front of local queue // Splice task post_exec queue at front of local queue
@ -755,6 +756,7 @@ namespace crucible {
// There is no longer a current consumer, but hold our own shared // There is no longer a current consumer, but hold our own shared
// state so it's still there in the destructor // state so it's still there in the destructor
swap(this_consumer, tl_current_consumer); swap(this_consumer, tl_current_consumer);
assert(!tl_current_consumer);
// Release lock to rescue queue (may attempt to queue a new task at TaskMaster). // Release lock to rescue queue (may attempt to queue a new task at TaskMaster).
// rescue_queue normally sends tasks to the local queue of the current TaskConsumer thread, // rescue_queue normally sends tasks to the local queue of the current TaskConsumer thread,