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Commit 4ee1f664 authored by Davis King's avatar Davis King
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Made thread_pool and parallel_for propagate exceptions from task threads to 

calling code.
parent 5b361945
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Showing with 83 additions and 32 deletions
dlib/test/thread_pool.cpp
View file @ 4ee1f664
......@@ -369,6 +369,39 @@ namespace
DLIB_TEST(d == 4);
}
tp.wait_for_all_tasks();
// make sure exception propagation from tasks works correctly.
auto f_throws = []() { throw dlib::error("test exception");};
bool got_exception = false;
try
{
tp.add_task_by_value(f_throws);
tp.wait_for_all_tasks();
}
catch(dlib::error& e)
{
DLIB_TEST(e.info == "test exception");
got_exception = true;
}
DLIB_TEST(got_exception);
dlib::future<int> aa;
auto f_throws2 = [](int& a) { a = 1; throw dlib::error("test exception");};
got_exception = false;
try
{
tp.add_task(f_throws2, aa);
aa.get();
}
catch(dlib::error& e)
{
DLIB_TEST(e.info == "test exception");
got_exception = true;
}
DLIB_TEST(got_exception);
}
}
......
dlib/threads/parallel_for_extension_abstract.h
View file @ 4ee1f664
......@@ -24,7 +24,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This is a convenience function for submitting a block of jobs to a thread_pool.
In particular, given the half open range [begin, end), this function will
......@@ -61,7 +60,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is equivalent to the following block of code:
thread_pool tp(num_threads);
......@@ -82,7 +80,6 @@ namespace dlib
requires
- chunks_per_thread > 0
- begin <= end
- funct does not throw any exceptions
ensures
- This is a convenience function for submitting a block of jobs to a
thread_pool. In particular, given the range [begin, end), this function will
......@@ -117,7 +114,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is equivalent to the following block of code:
thread_pool tp(num_threads);
......@@ -137,7 +133,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is equivalent to the following block of code:
parallel_for_blocked(default_thread_pool(), begin, end, funct, chunks_per_thread);
......@@ -159,7 +154,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is equivalent to the following function call:
parallel_for_blocked(tp, begin, end, [&](long begin_sub, long end_sub)
......@@ -189,7 +183,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is equivalent to the following block of code:
thread_pool tp(num_threads);
......@@ -210,7 +203,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is equivalent to the following function call:
parallel_for_blocked(tp, begin, end, [&](long begin_sub, long end_sub)
......@@ -238,7 +230,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is equivalent to the following block of code:
thread_pool tp(num_threads);
......@@ -258,7 +249,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is equivalent to the following block of code:
parallel_for(default_thread_pool(), begin, end, funct, chunks_per_thread);
......@@ -280,7 +270,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is identical to the parallel_for() routine defined above except
that it will print messages to cout showing the progress in executing the
......@@ -302,7 +291,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is identical to the parallel_for() routine defined above except
that it will print messages to cout showing the progress in executing the
......@@ -323,7 +311,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is identical to the parallel_for() routine defined above except
that it will print messages to cout showing the progress in executing the
......@@ -344,7 +331,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is identical to the parallel_for() routine defined above except
that it will print messages to cout showing the progress in executing the
......@@ -364,7 +350,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is identical to the parallel_for() routine defined above except
that it will print messages to cout showing the progress in executing the
......@@ -388,7 +373,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is identical to the parallel_for_blocked() routine defined
above except that it will print messages to cout showing the progress in
......@@ -410,7 +394,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is identical to the parallel_for_blocked() routine defined
above except that it will print messages to cout showing the progress in
......@@ -431,7 +414,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is identical to the parallel_for_blocked() routine defined
above except that it will print messages to cout showing the progress in
......@@ -452,7 +434,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is identical to the parallel_for_blocked() routine defined
above except that it will print messages to cout showing the progress in
......@@ -472,7 +453,6 @@ namespace dlib
requires
- begin <= end
- chunks_per_thread > 0
- funct does not throw any exceptions
ensures
- This function is identical to the parallel_for_blocked() routine defined
above except that it will print messages to cout showing the progress in
......
dlib/threads/thread_pool_extension.cpp
View file @ 4ee1f664
......@@ -61,6 +61,11 @@ namespace dlib
}
wait();
// Throw any unhandled exceptions. Since shutdown_pool() is only called in the
// destructor this will kill the program.
for (auto&& task : tasks)
task.propagate_exception();
}
// ----------------------------------------------------------------------------------------
......@@ -94,6 +99,9 @@ namespace dlib
const unsigned long idx = task_id_to_index(task_id);
while (tasks[idx].task_id == task_id)
task_done_signaler.wait();
for (auto&& task : tasks)
task.propagate_exception();
}
}
......@@ -124,6 +132,10 @@ namespace dlib
if (found_task)
task_done_signaler.wait();
}
// throw any exceptions generated by the tasks
for (auto&& task : tasks)
task.propagate_exception();
}
// ----------------------------------------------------------------------------------------
......@@ -177,15 +189,23 @@ namespace dlib
task = tasks[idx];
}
// now do the task
if (task.bfp)
task.bfp();
else if (task.mfp0)
task.mfp0();
else if (task.mfp1)
task.mfp1(task.arg1);
else if (task.mfp2)
task.mfp2(task.arg1, task.arg2);
std::exception_ptr eptr;
try
{
// now do the task
if (task.bfp)
task.bfp();
else if (task.mfp0)
task.mfp0();
else if (task.mfp1)
task.mfp1(task.arg1);
else if (task.mfp2)
task.mfp2(task.arg1, task.arg2);
}
catch(...)
{
eptr = std::current_exception();
}
// Now let others know that we finished the task. We do this
// by clearing out the state of this task
......@@ -198,6 +218,7 @@ namespace dlib
tasks[idx].mfp2.clear();
tasks[idx].arg1 = 0;
tasks[idx].arg2 = 0;
tasks[idx].eptr = eptr;
task_done_signaler.broadcast();
}
......@@ -210,6 +231,9 @@ namespace dlib
find_empty_task_slot (
) const
{
for (auto&& task : tasks)
task.propagate_exception();
for (unsigned long i = 0; i < tasks.size(); ++i)
{
if (tasks[i].is_empty())
......
dlib/threads/thread_pool_extension.h
View file @ 4ee1f664
......@@ -13,6 +13,7 @@
#include "../array.h"
#include "../smart_pointers_thread_safe.h"
#include "../smart_pointers.h"
#include <exception>
namespace dlib
{
......@@ -451,6 +452,17 @@ namespace dlib
bfp_type bfp;
shared_ptr<function_object_copy> function_copy;
mutable std::exception_ptr eptr; // non-null if the task threw an exception
void propagate_exception() const
{
if (eptr)
{
auto tmp = eptr;
eptr = nullptr;
std::rethrow_exception(tmp);
}
}
};
......
dlib/threads/thread_pool_extension_abstract.h
View file @ 4ee1f664
......@@ -225,9 +225,11 @@ namespace dlib
such as mutex objects.
EXCEPTIONS
Note that if an exception is thrown inside a task thread and
is not caught then the normal rule for uncaught exceptions in
threads applies. That is, the application will be terminated.
Note that if an exception is thrown inside a task thread and is not caught
then the exception will be trapped inside the thread pool and rethrown at a
later time when someone calls one of the add task or wait member functions
of the thread pool. This allows exceptions to propagate out of task threads
and into the calling code where they can be handled.
!*/
public:
......
examples/thread_pool_ex.cpp
View file @ 4ee1f664
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