From: Tom de Vries <tdevries@suse.de>
To: gdb-patches@sourceware.org
Subject: [PATCH][gdbsupport] Avoid main thread in parallel for with thread sanitizer
Date: Mon, 18 Jul 2022 12:05:22 +0200 [thread overview]
Message-ID: <20220718100520.GA26230@delia.home> (raw)
Hi,
When running tasks in a parallel for, some elements may be handled by a worker
thread and others by the main thread.
When running with -fsanitize=thread, avoid the main thread in the parallel
for, to prevent multi-threading problems being hidden.
Tested on x86_64-linux, with -fsanitize=thread.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29359
Any comments?
Thanks,
- Tom
[gdbsupport] Avoid main thread in parallel for with thread sanitizer
---
gdbsupport/parallel-for.h | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)
diff --git a/gdbsupport/parallel-for.h b/gdbsupport/parallel-for.h
index bf40f125f0f..81a2cfa215b 100644
--- a/gdbsupport/parallel-for.h
+++ b/gdbsupport/parallel-for.h
@@ -24,6 +24,15 @@
#include <type_traits>
#include "gdbsupport/thread-pool.h"
+/* GCC does not understand __has_feature. */
+#if !defined(__has_feature)
+# define __has_feature(x) 0
+#endif
+
+#if __has_feature(thread_sanitizer)
+#define __SANITIZE_ADDRESS__ 1
+#endif
+
namespace gdb
{
@@ -161,7 +170,22 @@ parallel_for_each (unsigned n, RandomIt first, RandomIt last,
/* n_elements == n_threads * elts_per_thread + elts_left_over. */
}
- size_t count = n_threads == 0 ? 0 : n_threads - 1;
+ /* Number of worker threads we're going to use. */
+ size_t count;
+#ifdef __SANITIZE_THREAD__
+ /* Avoid the main thread. */
+ count = (n_threads == 0
+ ? (/* Only use the first worker thread. */
+ 1)
+ : (/* Only use worker threads. */
+ n_threads));
+#else
+ count = (n_threads == 0
+ ? (/* Only use the main thread. */
+ 0)
+ : (/* Leave at least one worker thread unused. */
+ n_threads - 1));
+#endif
gdb::detail::par_for_accumulator<result_type> results (count);
if (parallel_for_each_debug)
next reply other threads:[~2022-07-18 10:05 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-18 10:05 Tom de Vries [this message]
2022-07-18 10:31 ` Tom de Vries
2022-09-21 16:09 ` Tom Tromey
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