3 Copyright (C) 2019 Free Software Foundation, Inc.
5 This file is part of GDB.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>. */
20 #include "common-defs.h"
24 #include "gdbsupport/thread-pool.h"
25 #include "gdbsupport/alt-stack.h"
26 #include "gdbsupport/block-signals.h"
32 /* The thread pool detach()s its threads, so that the threads will not
33 prevent the process from exiting. However, it was discovered that
34 if any detached threads were still waiting on a condition variable,
35 then the condition variable's destructor would wait for the threads
36 to exit -- defeating the purpose.
38 Allocating the thread pool on the heap and simply "leaking" it
41 thread_pool
*thread_pool::g_thread_pool
= new thread_pool ();
43 thread_pool::~thread_pool ()
45 /* Because this is a singleton, we don't need to clean up. The
46 threads are detached so that they won't prevent process exit.
47 And, cleaning up here would be actively harmful in at least one
48 case -- see the comment by the definition of g_thread_pool. */
52 thread_pool::set_thread_count (size_t num_threads
)
54 std::lock_guard
<std::mutex
> guard (m_tasks_mutex
);
56 /* If the new size is larger, start some new threads. */
57 if (m_thread_count
< num_threads
)
59 /* Ensure that signals used by gdb are blocked in the new
61 block_signals blocker
;
62 for (size_t i
= m_thread_count
; i
< num_threads
; ++i
)
64 std::thread
thread (&thread_pool::thread_function
, this);
68 /* If the new size is smaller, terminate some existing threads. */
69 if (num_threads
< m_thread_count
)
71 for (size_t i
= num_threads
; i
< m_thread_count
; ++i
)
73 m_tasks_cv
.notify_all ();
76 m_thread_count
= num_threads
;
80 thread_pool::post_task (std::function
<void ()> func
)
82 std::packaged_task
<void ()> t (func
);
83 std::future
<void> f
= t
.get_future ();
85 if (m_thread_count
== 0)
87 /* Just execute it now. */
92 std::lock_guard
<std::mutex
> guard (m_tasks_mutex
);
93 m_tasks
.emplace (std::move (t
));
94 m_tasks_cv
.notify_one ();
100 thread_pool::thread_function ()
102 /* Ensure that SIGSEGV is delivered to an alternate signal
104 gdb::alternate_signal_stack signal_stack
;
111 /* We want to hold the lock while examining the task list, but
112 not while invoking the task function. */
113 std::unique_lock
<std::mutex
> guard (m_tasks_mutex
);
114 while (m_tasks
.empty ())
115 m_tasks_cv
.wait (guard
);
116 t
= std::move (m_tasks
.front());
128 #endif /* CXX_STD_THREAD */