Hi!
On 2022-01-13T13:53:03+0000, Andrew Stubbs <ams@codesourcery.com> wrote:
> Pinned memory is allocated via mmap
> --- /dev/null
> +++ b/libgomp/config/linux/allocator.c
> +static void *
> +linux_memspace_calloc (omp_memspace_handle_t memspace, size_t size, int pin)
> +{
> + if (pin)
> + return linux_memspace_alloc (memspace, size, pin);
> +[...]
This confused me for a moment, why we don't have to manually
zero-initialize here. I've pushed to devel/omp/gcc-12 branch
commit 57b8f0600262566cd4f1ab12bf1bdafb29dbdc34
"Clarify/verify OpenMP 'omp_calloc' zero-initialization for pinned memory",
see attached.
Grüße
Thomas
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From 57b8f0600262566cd4f1ab12bf1bdafb29dbdc34 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <thomas@codesourcery.com>
Date: Wed, 15 Feb 2023 10:23:03 +0100
Subject: [PATCH] Clarify/verify OpenMP 'omp_calloc' zero-initialization for
pinned memory
Clarification for og12 commit ab7520b3b4cd9fdabfd63652badde478955bd3b5
"libgomp: pinned memory". No functional change.
libgomp/
* config/linux/allocator.c (linux_memspace_alloc)
(linux_memspace_calloc): Clarify zero-initialization for pinned
memory.
* testsuite/libgomp.c/alloc-pinned-1.c: Verify zero-initialization
for pinned memory.
* testsuite/libgomp.c/alloc-pinned-2.c: Likewise.
* testsuite/libgomp.c/alloc-pinned-3.c: Likewise.
* testsuite/libgomp.c/alloc-pinned-4.c: Likewise.
* testsuite/libgomp.c/alloc-pinned-5.c: Likewise.
---
libgomp/ChangeLog.omp | 10 ++++++++++
libgomp/config/linux/allocator.c | 2 ++
libgomp/testsuite/libgomp.c/alloc-pinned-1.c | 10 ++++++++++
libgomp/testsuite/libgomp.c/alloc-pinned-2.c | 10 ++++++++++
libgomp/testsuite/libgomp.c/alloc-pinned-3.c | 9 +++++++++
libgomp/testsuite/libgomp.c/alloc-pinned-4.c | 9 +++++++++
libgomp/testsuite/libgomp.c/alloc-pinned-5.c | 10 ++++++++++
7 files changed, 60 insertions(+)
@@ -1,5 +1,15 @@
2023-02-16 Thomas Schwinge <thomas@codesourcery.com>
+ * config/linux/allocator.c (linux_memspace_alloc)
+ (linux_memspace_calloc): Clarify zero-initialization for pinned
+ memory.
+ * testsuite/libgomp.c/alloc-pinned-1.c: Verify zero-initialization
+ for pinned memory.
+ * testsuite/libgomp.c/alloc-pinned-2.c: Likewise.
+ * testsuite/libgomp.c/alloc-pinned-3.c: Likewise.
+ * testsuite/libgomp.c/alloc-pinned-4.c: Likewise.
+ * testsuite/libgomp.c/alloc-pinned-5.c: Likewise.
+
* config/linux/allocator.c (linux_memspace_calloc): Elide
(innocuous) duplicate 'if' condition.
* config/nvptx/allocator.c (nvptx_memspace_free): Explicitly
@@ -65,6 +65,7 @@ linux_memspace_alloc (omp_memspace_handle_t memspace, size_t size, int pin)
}
else if (pin)
{
+ /* 'mmap' zero-initializes, which 'linux_memspace_calloc' relies on. */
void *addr = mmap (NULL, size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (addr == MAP_FAILED)
@@ -96,6 +97,7 @@ linux_memspace_calloc (omp_memspace_handle_t memspace, size_t size, int pin)
return ret;
}
else if (pin)
+ /* If PINned, 'linux_memspace_alloc' 'mmap's, which zero-initializes. */
return linux_memspace_alloc (memspace, size, pin);
else
return calloc (1, size);
@@ -54,6 +54,14 @@ get_pinned_mem ()
}
#endif
+static void
+verify0 (char *p, size_t s)
+{
+ for (size_t i = 0; i < s; ++i)
+ if (p[i] != 0)
+ abort ();
+}
+
#include <omp.h>
int
@@ -91,5 +99,7 @@ main ()
if (get_pinned_mem () <= amount2)
abort ();
+ verify0 (p, SIZE);
+
return 0;
}
@@ -54,6 +54,14 @@ get_pinned_mem ()
}
#endif
+static void
+verify0 (char *p, size_t s)
+{
+ for (size_t i = 0; i < s; ++i)
+ if (p[i] != 0)
+ abort ();
+}
+
#include <omp.h>
int
@@ -97,5 +105,7 @@ main ()
if (get_pinned_mem () <= amount2)
abort ();
+ verify0 (p, SIZE);
+
return 0;
}
@@ -61,6 +61,14 @@ set_pin_limit ()
}
#endif
+static void
+verify0 (char *p, size_t s)
+{
+ for (size_t i = 0; i < s; ++i)
+ if (p[i] != 0)
+ abort ();
+}
+
#include <omp.h>
int
@@ -109,6 +117,7 @@ main ()
p = omp_calloc (1, SIZE, allocator2);
if (!p)
abort ();
+ verify0 (p, SIZE);
// Should fail to realloc
void *notpinned = omp_alloc (SIZE, omp_default_mem_alloc);
@@ -61,6 +61,14 @@ set_pin_limit ()
}
#endif
+static void
+verify0 (char *p, size_t s)
+{
+ for (size_t i = 0; i < s; ++i)
+ if (p[i] != 0)
+ abort ();
+}
+
#include <omp.h>
int
@@ -111,6 +119,7 @@ main ()
p = omp_calloc (1, SIZE, allocator2);
if (!p)
abort ();
+ verify0 (p, SIZE);
// Should fail to realloc
void *notpinned = omp_alloc (SIZE, omp_default_mem_alloc);
@@ -54,6 +54,14 @@ get_pinned_mem ()
}
#endif
+static void
+verify0 (char *p, size_t s)
+{
+ for (size_t i = 0; i < s; ++i)
+ if (p[i] != 0)
+ abort ();
+}
+
#include <omp.h>
int
@@ -86,5 +94,7 @@ main ()
if (get_pinned_mem () <= amount2)
abort ();
+ verify0 (p, SIZE);
+
return 0;
}
--
2.25.1