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authorFlorian Weimer <fweimer@redhat.com>2020-05-20 15:40:35 +0200
committerFlorian Weimer <fweimer@redhat.com>2020-07-06 11:15:58 +0200
commit706ad1e7af37be1d25fc2359bda006d31fe0d11b (patch)
treed06e6a96c1d319a1d27fa6b6e87cfadf8bd6ef08 /elf/tst-single_threaded.c
parent8f4632deb3545b2949cec5454afc3cb21a0024ea (diff)
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Add the __libc_single_threaded variable
The variable is placed in libc.so, and it can be true only in
an outer libc, not libcs loaded via dlmopen or static dlopen.
Since thread creation from inner namespaces does not work,
pthread_create can update __libc_single_threaded directly.

Using __libc_early_init and its initial flag, implementation of this
variable is very straightforward.  A future version may reset the flag
during fork (but not in an inner namespace), or after joining all
threads except one.

Reviewed-by: DJ Delorie <dj@redhat.com>
Diffstat (limited to 'elf/tst-single_threaded.c')
-rw-r--r--elf/tst-single_threaded.c70
1 files changed, 70 insertions, 0 deletions
diff --git a/elf/tst-single_threaded.c b/elf/tst-single_threaded.c
new file mode 100644
index 0000000000..2c36342779
--- /dev/null
+++ b/elf/tst-single_threaded.c
@@ -0,0 +1,70 @@
+/* Test support for single-thread optimizations.  No threads.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stddef.h>
+#include <stdio.h>
+#include <support/check.h>
+#include <support/namespace.h>
+#include <support/xdlfcn.h>
+#include <sys/single_threaded.h>
+
+/* Defined in tst-single-threaded-mod1.so.  */
+extern _Bool single_threaded_1 (void);
+
+/* Initialized via dlsym.  */
+_Bool (*single_threaded_2) (void);
+_Bool (*single_threaded_3) (void);
+
+static void
+subprocess (void *closure)
+{
+  TEST_VERIFY (__libc_single_threaded);
+  TEST_VERIFY (single_threaded_1 ());
+  if (single_threaded_2 != NULL)
+    TEST_VERIFY (single_threaded_2 ());
+  if (single_threaded_3 != NULL)
+    TEST_VERIFY (!single_threaded_3 ());
+}
+
+static int
+do_test (void)
+{
+  TEST_VERIFY (__libc_single_threaded);
+  TEST_VERIFY (single_threaded_1 ());
+  support_isolate_in_subprocess (subprocess, NULL);
+
+  void *handle_mod2 = xdlopen ("tst-single_threaded-mod2.so", RTLD_LAZY);
+  single_threaded_2 = xdlsym (handle_mod2, "single_threaded_2");
+  TEST_VERIFY (single_threaded_2 ());
+  support_isolate_in_subprocess (subprocess, NULL);
+
+  /* The current implementation treats the inner namespace as
+     multi-threaded.  */
+  void *handle_mod3 = dlmopen (LM_ID_NEWLM, "tst-single_threaded-mod3.so",
+                               RTLD_LAZY);
+  single_threaded_3 = xdlsym (handle_mod3, "single_threaded_3");
+  TEST_VERIFY (!single_threaded_3 ());
+  support_isolate_in_subprocess (subprocess, NULL);
+
+  xdlclose (handle_mod3);
+  xdlclose (handle_mod2);
+
+  return 0;
+}
+
+#include <support/test-driver.c>