Hi Tobias!
On 2022-10-24T21:05:46+0200, I wrote:
> On 2022-10-24T16:07:25+0200, Jakub Jelinek via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
>> On Wed, Oct 12, 2022 at 10:55:26AM +0200, Tobias Burnus wrote:
>>> libgomp/nvptx: Prepare for reverse-offload callback handling
>
>> Ok, thanks.
>
> Per commit r13-3460-g131d18e928a3ea1ab2d3bf61aa92d68a8a254609
> "libgomp/nvptx: Prepare for reverse-offload callback handling",
> I'm seeing a lot of libgomp execution test regressions. Random
> example, 'libgomp.c-c++-common/error-1.c':
>
> [...]
> GOMP_OFFLOAD_run: kernel main$_omp_fn$0: launch [(teams: 1), 1, 1]
> [(lanes: 32), (threads: 8), 1]
>
> Thread 1 "a.out" received signal SIGSEGV, Segmentation fault.
> 0x00007ffff793b87d in GOMP_OFFLOAD_run (ord=<optimized out>,
> tgt_fn=<optimized out>, tgt_vars=<optimized out>, args=<optimized out>) at
> [...]/source-gcc/libgomp/plugin/plugin-nvptx.c:2127
> 2127 if (__atomic_load_n (&ptx_dev->rev_data->fn,
> __ATOMIC_ACQUIRE) != 0)
> (gdb) print ptx_dev
> $1 = (struct ptx_device *) 0x6a55a0
> (gdb) print ptx_dev->rev_data
> $2 = (struct rev_offload *) 0xffffffff00000000
> (gdb) print ptx_dev->rev_data->fn
> Cannot access memory at address 0xffffffff00000000
>
> Why is it even taking this 'if (reverse_offload)' code path, which isn't
> applicable to this test case (as far as I understand)? (Well, the answer
> is 'bool reverse_offload = ptx_dev->rev_data != NULL;', but why is that?)
Well.
--- a/libgomp/plugin/plugin-nvptx.c
+++ b/libgomp/plugin/plugin-nvptx.c
@@ -329,6 +332,7 @@ struct ptx_device
pthread_mutex_t lock;
} omp_stacks;
+ struct rev_offload *rev_data;
struct ptx_device *next;
};
... but as far as I can tell, this is never initialized in
'nvptx_open_device', which does 'ptx_dev = GOMP_PLUGIN_malloc ([...]);'.
Would the following be the correct fix (currently testing)?
--- libgomp/plugin/plugin-nvptx.c
+++ libgomp/plugin/plugin-nvptx.c
@@ -546,6 +546,8 @@ nvptx_open_device (int n)
ptx_dev->omp_stacks.size = 0;
pthread_mutex_init (&ptx_dev->omp_stacks.lock, NULL);
+ ptx_dev->rev_data = NULL;
+
return ptx_dev;
}
Grüße
Thomas
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