diff options
| -rw-r--r-- | gdb/unittests/parallel-for-selftests.c | 39 | ||||
| -rw-r--r-- | gdbsupport/parallel-for.h | 30 |
2 files changed, 69 insertions, 0 deletions
diff --git a/gdb/unittests/parallel-for-selftests.c b/gdb/unittests/parallel-for-selftests.c index 3162db18df1..15a095ae62b 100644 --- a/gdb/unittests/parallel-for-selftests.c +++ b/gdb/unittests/parallel-for-selftests.c @@ -149,6 +149,45 @@ TEST (int n_threads) SELF_CHECK (counter == NUMBER); #undef NUMBER + + /* Check that if there are fewer tasks than threads, then we won't + end up with a null result. */ + std::vector<std::unique_ptr<int>> intresults; + std::atomic<bool> any_empty_tasks (false); + + FOR_EACH (1, 0, 1, + [&] (int start, int end) + { + if (start == end) + any_empty_tasks = true; + return std::unique_ptr<int> (new int (end - start)); + }); + SELF_CHECK (!any_empty_tasks); + SELF_CHECK (std::all_of (intresults.begin (), + intresults.end (), + [] (const std::unique_ptr<int> &entry) + { + return entry != nullptr; + })); + + /* The same but using the task size parameter. */ + intresults.clear (); + any_empty_tasks = false; + FOR_EACH (1, 0, 1, + [&] (int start, int end) + { + if (start == end) + any_empty_tasks = true; + return std::unique_ptr<int> (new int (end - start)); + }, + task_size_one); + SELF_CHECK (!any_empty_tasks); + SELF_CHECK (std::all_of (intresults.begin (), + intresults.end (), + [] (const std::unique_ptr<int> &entry) + { + return entry != nullptr; + })); } #endif /* FOR_EACH */ diff --git a/gdbsupport/parallel-for.h b/gdbsupport/parallel-for.h index b565676a0d0..de9ebb15746 100644 --- a/gdbsupport/parallel-for.h +++ b/gdbsupport/parallel-for.h @@ -70,6 +70,12 @@ public: return result; } + /* Resize the results to N. */ + void resize (size_t n) + { + m_futures.resize (n); + } + private: /* A vector of futures coming from the tasks run in the @@ -108,6 +114,12 @@ public: } } + /* Resize the results to N. */ + void resize (size_t n) + { + m_futures.resize (n); + } + private: std::vector<gdb::future<void>> m_futures; @@ -232,6 +244,24 @@ parallel_for_each (unsigned n, RandomIt first, RandomIt last, end = j; remaining_size -= chunk_size; } + + /* This case means we don't have enough elements to really + distribute them. Rather than ever submit a task that does + nothing, we short-circuit here. */ + if (first == end) + end = last; + + if (end == last) + { + /* We're about to dispatch the last batch of elements, which + we normally process in the main thread. So just truncate + the result list here. This avoids submitting empty tasks + to the thread pool. */ + count = i; + results.resize (count); + break; + } + if (parallel_for_each_debug) { debug_printf (_("Parallel for: elements on worker thread %i\t: %zu"), |