ca4b55ce0a
- New nbdkit-count-filter. - Remove nbdkit-cacheextents-filter. - file: trim: Don't try BLKDISCARD if earlier FALLOC_FL_PUNCH_HOLE worked related: RHEL-101180
273 lines
8.2 KiB
Diff
273 lines
8.2 KiB
Diff
From de37da4184c55c6811dd02707fdd3b1773a7ce66 Mon Sep 17 00:00:00 2001
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From: "Richard W.M. Jones" <rjones@redhat.com>
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Date: Fri, 4 Jul 2025 08:13:48 +0100
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Subject: [PATCH] common: Add ONCE macro to run code only once
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This macro can be used to run code once, especially for debug messages
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and similar. eg:
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/* Print this once in the log. */
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ONCE (nbdkit_debug ("falling back to less efficient method"));
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(cherry picked from commit ad8630deab4639e636212f11a5a47d2c34ef2949)
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---
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.gitignore | 1 +
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common/include/Makefile.am | 6 ++
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common/include/once.h | 67 ++++++++++++++++++++
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common/include/test-once.c | 126 +++++++++++++++++++++++++++++++++++++
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4 files changed, 200 insertions(+)
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create mode 100644 common/include/once.h
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create mode 100644 common/include/test-once.c
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diff --git a/.gitignore b/.gitignore
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index 3629ef39..827fd53c 100644
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--- a/.gitignore
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+++ b/.gitignore
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@@ -68,6 +68,7 @@ plugins/*/*.3
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/common/include/test-iszero
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/common/include/test-minmax
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/common/include/test-nextnonzero
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+/common/include/test-once
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/common/include/test-random
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/common/include/test-tvdiff
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/common/protocol/generate-protostrings.sh
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diff --git a/common/include/Makefile.am b/common/include/Makefile.am
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index ca488e68..3a3757e2 100644
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--- a/common/include/Makefile.am
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+++ b/common/include/Makefile.am
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@@ -49,6 +49,7 @@ EXTRA_DIST = \
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iszero.h \
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minmax.h \
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nextnonzero.h \
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+ once.h \
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random.h \
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rounding.h \
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static-assert.h \
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@@ -71,6 +72,7 @@ TESTS = \
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test-iszero \
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test-minmax \
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test-nextnonzero \
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+ test-once \
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test-random \
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test-tvdiff \
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$(NULL)
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@@ -120,6 +122,10 @@ test_nextnonzero_SOURCES = test-nextnonzero.c nextnonzero.h
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test_nextnonzero_CPPFLAGS = -I$(srcdir)
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test_nextnonzero_CFLAGS = $(WARNINGS_CFLAGS)
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+test_once_SOURCES = test-once.c once.h
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+test_once_CPPFLAGS = -I$(srcdir)
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+test_once_CFLAGS = $(WARNINGS_CFLAGS)
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+
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test_random_SOURCES = test-random.c random.h
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test_random_CPPFLAGS = -I$(srcdir)
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test_random_CFLAGS = $(WARNINGS_CFLAGS)
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diff --git a/common/include/once.h b/common/include/once.h
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new file mode 100644
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index 00000000..bb93e767
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--- /dev/null
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+++ b/common/include/once.h
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@@ -0,0 +1,67 @@
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+/* nbdkit
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+ * Copyright Red Hat
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+ *
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+ * Redistribution and use in source and binary forms, with or without
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+ * modification, are permitted provided that the following conditions are
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+ * met:
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+ *
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+ * * Redistributions of source code must retain the above copyright
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+ * notice, this list of conditions and the following disclaimer.
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+ *
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+ * * Redistributions in binary form must reproduce the above copyright
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+ * notice, this list of conditions and the following disclaimer in the
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+ * documentation and/or other materials provided with the distribution.
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+ *
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+ * * Neither the name of Red Hat nor the names of its contributors may be
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+ * used to endorse or promote products derived from this software without
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+ * specific prior written permission.
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+ *
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+ * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
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+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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+ * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
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+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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+ * SUCH DAMAGE.
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+ */
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+
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+#ifndef NBDKIT_ONCE_H
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+#define NBDKIT_ONCE_H
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+
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+#ifdef HAVE_STDATOMIC_H
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+#include <stdatomic.h>
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+#else
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+/* This is best effort on platforms that don't support atomic.
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+ * 32 bit ints are generally fine in reality.
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+ */
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+#define _Atomic /**/
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+#endif
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+
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+#include "unique-name.h"
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+
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+/* Run the statement once (per nbdkit run). */
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+#define ONCE(stmt) ONCE_1(NBDKIT_UNIQUE_NAME(_once), (stmt))
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+
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+/* The actual implementation:
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+ *
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+ * The comparison with 0 avoids var wrapping around. Mostly var will
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+ * only be 0 or 1, or in rare cases other small integers.
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+ *
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+ * The atomic increment & comparison with 1 is what only allows a
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+ * single thread to run the statement.
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+ *
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+ * To avoid optimisations: Use 'volatile' so reads and writes are not
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+ * removed, and use 'unsigned' to avoid any with signed overflow.
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+ */
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+#define ONCE_1(var, stmt) \
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+ do { \
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+ static volatile _Atomic unsigned var = 0; \
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+ if (var == 0 && ++var == 1) { stmt; } \
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+ } while (0)
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+
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+#endif /* NBDKIT_ONCE_H */
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diff --git a/common/include/test-once.c b/common/include/test-once.c
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new file mode 100644
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index 00000000..d7dd5c42
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--- /dev/null
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+++ b/common/include/test-once.c
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@@ -0,0 +1,126 @@
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+/* nbdkit
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+ * Copyright Red Hat
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+ *
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+ * Redistribution and use in source and binary forms, with or without
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+ * modification, are permitted provided that the following conditions are
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+ * met:
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+ *
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+ * * Redistributions of source code must retain the above copyright
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+ * notice, this list of conditions and the following disclaimer.
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+ *
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+ * * Redistributions in binary form must reproduce the above copyright
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+ * notice, this list of conditions and the following disclaimer in the
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+ * documentation and/or other materials provided with the distribution.
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+ *
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+ * * Neither the name of Red Hat nor the names of its contributors may be
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+ * used to endorse or promote products derived from this software without
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+ * specific prior written permission.
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+ *
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+ * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
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+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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+ * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
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+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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+ * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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+ * SUCH DAMAGE.
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+ */
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+
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+#include <config.h>
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+
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+#include <stdio.h>
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+#include <stdlib.h>
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+
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+#ifndef HAVE_STDATOMIC_H
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+
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+/* Skip the test if no <stdatomic.h> */
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+
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+int
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+main (void)
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+{
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+ printf ("SKIP: no <stdatomic.h> on this platform\n");
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+ exit (77);
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+}
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+
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+#else /* HAVE_STDATOMIC_H */
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+
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+#include <stdatomic.h>
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+#include <errno.h>
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+#include <unistd.h>
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+
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+#undef NDEBUG /* Keep test strong even for nbdkit built without assertions */
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+#include <assert.h>
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+
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+#include <pthread.h>
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+
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+#include "once.h"
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+
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+#define NR_THREADS 8
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+
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+static volatile _Atomic unsigned count1 = 0, count2 = 0,
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+ count3 = 0, count4 = 0;
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+static pthread_barrier_t barrier;
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+
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+static void * __attribute__((noreturn))
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+start_thread (void *idxp)
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+{
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+ //int idx = * (int*) idxp;
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+
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+ pthread_barrier_wait (&barrier);
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+
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+ for (;;) {
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+ ONCE (count1++);
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+ ONCE (count2++);
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+ ONCE (count3++);
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+ ONCE (count4++);
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+ }
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+}
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+
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+int
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+main (void)
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+{
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+ int i, err;
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+ pthread_t th[NR_THREADS];
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+ int idx[NR_THREADS];
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+
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+ err = pthread_barrier_init (&barrier, NULL, NR_THREADS);
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+ if (err != 0) {
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+ errno = err;
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+ perror ("pthread_barrier_init");
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+ exit (EXIT_FAILURE);
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+ }
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+
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+ for (i = 0; i < NR_THREADS; ++i) {
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+ idx[i] = i;
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+ err = pthread_create (&th[i], NULL, start_thread, &idx[i]);
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+ if (err != 0) {
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+ errno = err;
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+ perror ("pthread_create");
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+ exit (EXIT_FAILURE);
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+ }
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+ }
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+
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+ do {
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+ sleep (1);
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+ } while (count1 + count2 + count3 + count4 < 4);
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+
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+ for (i = 0; i < NR_THREADS; ++i) {
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+ pthread_cancel (th[i]);
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+ }
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+
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+ pthread_barrier_destroy (&barrier);
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+
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+ if (count1 != 1 || count2 != 1 || count3 != 1 || count4 != 1) {
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+ fprintf (stderr, "FAIL: counts incremented to %u %u %u %u "
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+ "(expected 1 1 1 1)\n", count1, count2, count3, count4);
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+ exit (EXIT_FAILURE);
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+ }
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+
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+ exit (EXIT_SUCCESS);
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+}
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+
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+#endif /* HAVE_STDATOMIC_H */
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--
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2.47.1
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