[og12] Clarify/verify OpenMP 'omp_calloc' zero-initialization for pinned memory (was: [PATCH] libgomp, openmp: pinned memory)

[Thomas Schwinge <thomas@codesourcery.com>]

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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(+)

diff --git a/libgomp/ChangeLog.omp b/libgomp/ChangeLog.omp
index 1c4b1833c0b..530f5c6acf6 100644
--- a/libgomp/ChangeLog.omp
+++ b/libgomp/ChangeLog.omp
@@ -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
diff --git a/libgomp/config/linux/allocator.c b/libgomp/config/linux/allocator.c
index 8a9171c36df..f278e5cdf14 100644
--- a/libgomp/config/linux/allocator.c
+++ b/libgomp/config/linux/allocator.c
@@ -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);
diff --git a/libgomp/testsuite/libgomp.c/alloc-pinned-1.c b/libgomp/testsuite/libgomp.c/alloc-pinned-1.c
index 79792b16d83..fb7ac8b0080 100644
--- a/libgomp/testsuite/libgomp.c/alloc-pinned-1.c
+++ b/libgomp/testsuite/libgomp.c/alloc-pinned-1.c
@@ -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;
 }
diff --git a/libgomp/testsuite/libgomp.c/alloc-pinned-2.c b/libgomp/testsuite/libgomp.c/alloc-pinned-2.c
index 228c656b715..651b89fb42f 100644
--- a/libgomp/testsuite/libgomp.c/alloc-pinned-2.c
+++ b/libgomp/testsuite/libgomp.c/alloc-pinned-2.c
@@ -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;
 }
diff --git a/libgomp/testsuite/libgomp.c/alloc-pinned-3.c b/libgomp/testsuite/libgomp.c/alloc-pinned-3.c
index 90539ffe3e0..f41797881ef 100644
--- a/libgomp/testsuite/libgomp.c/alloc-pinned-3.c
+++ b/libgomp/testsuite/libgomp.c/alloc-pinned-3.c
@@ -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);
diff --git a/libgomp/testsuite/libgomp.c/alloc-pinned-4.c b/libgomp/testsuite/libgomp.c/alloc-pinned-4.c
index 534e49eefc4..a878da8c558 100644
--- a/libgomp/testsuite/libgomp.c/alloc-pinned-4.c
+++ b/libgomp/testsuite/libgomp.c/alloc-pinned-4.c
@@ -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);
diff --git a/libgomp/testsuite/libgomp.c/alloc-pinned-5.c b/libgomp/testsuite/libgomp.c/alloc-pinned-5.c
index 315c7161a39..65983b3d03d 100644
--- a/libgomp/testsuite/libgomp.c/alloc-pinned-5.c
+++ b/libgomp/testsuite/libgomp.c/alloc-pinned-5.c
@@ -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