From: Tom de Vries <tdevries@suse.de>
To: Andrew Stubbs <ams@codesourcery.com>,
"gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>
Cc: Tobias Burnus <tobias@codesourcery.com>,
Jakub Jelinek <jakub@redhat.com>
Subject: Re: [PATCH] libgomp, OpenMP, nvptx: Low-latency memory allocator
Date: Thu, 6 Jan 2022 18:53:02 +0100 [thread overview]
Message-ID: <3e39c39d-2753-f08c-5fb7-85051cafab85@suse.de> (raw)
In-Reply-To: <5e75a64c-a8d3-2d2a-162a-a3ea79358b48@suse.de>
On 1/6/22 10:29, Tom de Vries wrote:
> At first glance, the above behaviour doesn't look like a too short timeout.
Using patch below, this passes for me, I'm currently doing a full build
and test to confirm.
Looks like it has to do with:
...
For sm_6x and earlier architectures, atom operations on .shared state
space do not guarantee atomicity with respect to normal store
instructions to the same address. It is the programmer's responsibility
to guarantee correctness of programs that use shared memory
atomic instructions, e.g., by inserting barriers between normal stores
and atomic operations to a common address, or by using atom.exch to
store to locations accessed by other atomic operations.
...
My current understanding is that this is a backend problem, and needs to
be fixed by defining atomic_store patterns which take care of this
peculiarity.
Thanks,
- Tom
diff --git a/libgomp/config/nvptx/allocator.c
b/libgomp/config/nvptx/allocator.c
index 6bc2ea48043..4524122b3e7 100644
--- a/libgomp/config/nvptx/allocator.c
+++ b/libgomp/config/nvptx/allocator.c
@@ -122,7 +122,8 @@ nvptx_memspace_alloc (omp_memspace_handle_t
memspace, size_t size)
}
/* Update the free chain root and release the lock. */
- __atomic_store_n (&__nvptx_lowlat_heap_root, root.raw,
MEMMODEL_RELEASE);
+ __atomic_exchange_n (&__nvptx_lowlat_heap_root,
+ root.raw, MEMMODEL_RELEASE);
return result;
}
else-
@@ -221,7 +222,8 @@ nvptx_memspace_free (omp_memspace_handle_t memspace,
void *addr, s
ize_t size)
root.raw = newfreechunk.raw;
/* Update the free chain root and release the lock. */
- __atomic_store_n (&__nvptx_lowlat_heap_root, root.raw,
MEMMODEL_RELEASE);
+ __atomic_exchange_n (&__nvptx_lowlat_heap_root,
+ root.raw, MEMMODEL_RELEASE);
}
else
free (addr);
@@ -331,7 +333,8 @@ nvptx_memspace_realloc (omp_memspace_handle_t
memspace, void *addr
,
/* Else realloc in-place has failed and result remains NULL. */
/* Update the free chain root and release the lock. */
- __atomic_store_n (&__nvptx_lowlat_heap_root, root.raw,
MEMMODEL_RELEASE);
+ __atomic_exchange_n (&__nvptx_lowlat_heap_root,
+ root.raw, MEMMODEL_RELEASE);
if (result == NULL)
{
next prev parent reply other threads:[~2022-01-06 17:53 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-20 15:58 Andrew Stubbs
2021-12-21 11:33 ` [PATCH] nvptx: bump default to PTX 4.1 Andrew Stubbs
2022-01-05 10:24 ` Tom de Vries
2022-01-05 10:33 ` Andrew Stubbs
2022-01-05 12:45 ` Tom de Vries
2022-01-05 11:08 ` [PATCH] libgomp, OpenMP, nvptx: Low-latency memory allocator Tom de Vries
2022-01-05 13:04 ` Tom de Vries
2022-01-05 14:36 ` Andrew Stubbs
2022-01-06 9:29 ` Tom de Vries
2022-01-06 17:53 ` Tom de Vries [this message]
2022-01-07 14:14 ` Andrew Stubbs
2022-01-13 11:13 ` Andrew Stubbs
2023-02-14 12:54 ` [og12] In 'libgomp/allocator.c:omp_realloc', route 'free' through 'MEMSPACE_FREE' (was: [PATCH] libgomp, OpenMP, nvptx: Low-latency memory allocator) Thomas Schwinge
2023-02-14 15:11 ` Andrew Stubbs
2023-02-16 21:45 ` Thomas Schwinge
2022-01-05 14:21 ` [PATCH] libgomp, OpenMP, nvptx: Low-latency memory allocator Andrew Stubbs
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