[Mesa-dev] [PATCH] libdrm/amdgpu: Use private fd for amdgpu_device and winsys hash table to fix ZaphodHeads.

[Christian König]

On 15.07.2015 07:15, Mario Kleiner wrote:
> The amdgpu_device for a device node needs its own dup'ed fd, instead
> of using the original fd passed in for a screen, to make multi-x-screen
> ZaphodHeads configurations work on amdgpu.
>
> The original fd's lifetime differs from that of the amdgpu_device, and from the
> one stored in the hash. The hash key is the fd, and in order to compare hash
> entries we fstat them, so the fd must be around for as long as the amdgpu_device
> is.
>
> This patch for libdrm/amdgpu is a translation of the radeon-winsys ZaphodHeads
> fix for mesa's radeon-winsys, from mesa commit 28dda47ae4d974e3e032d60e8e0965c8c068c6d8
>
> "winsys/radeon: Use dup fd as key in drm-winsys hash table to fix ZaphodHeads."
>
> Signed-off-by: Mario Kleiner <mario.kleiner.de at gmail.com>
> Cc: Marek Olšák <marek.olsak at amd.com>

Mhm, we originally designed libdrm_amdgpu with the idea that we take 
ownership of the file descriptor.

That was obviously not implemented like this (we leak the descriptor on 
destruction), but IIRC there was a reason for doing it like this.

The patch is Reviewed-by: Christian König <christian.koenig at amd.com> for 
now, but I'm not 100% sure if that's the last word on the topic.

Regards,
Christian.

> ---
>   amdgpu/amdgpu_device.c | 14 ++++++++++----
>   1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/amdgpu/amdgpu_device.c b/amdgpu/amdgpu_device.c
> index b50ce26..1b0cd12 100644
> --- a/amdgpu/amdgpu_device.c
> +++ b/amdgpu/amdgpu_device.c
> @@ -34,6 +34,7 @@
>   #include <string.h>
>   #include <stdio.h>
>   #include <stdlib.h>
> +#include <unistd.h>
>   
>   #include "xf86drm.h"
>   #include "amdgpu_drm.h"
> @@ -153,7 +154,7 @@ int amdgpu_device_initialize(int fd,
>   			return r;
>   		}
>   		if ((flag_auth) && (!flag_authexist)) {
> -			dev->flink_fd = fd;
> +			dev->flink_fd = dup(fd);
>   		}
>   		*major_version = dev->major_version;
>   		*minor_version = dev->minor_version;
> @@ -183,8 +184,8 @@ int amdgpu_device_initialize(int fd,
>   		goto cleanup;
>   	}
>   
> -	dev->fd = fd;
> -	dev->flink_fd = fd;
> +	dev->fd = dup(fd);
> +	dev->flink_fd = dev->fd;
>   	dev->major_version = version->version_major;
>   	dev->minor_version = version->version_minor;
>   	drmFreeVersion(version);
> @@ -213,12 +214,14 @@ int amdgpu_device_initialize(int fd,
>   	*major_version = dev->major_version;
>   	*minor_version = dev->minor_version;
>   	*device_handle = dev;
> -	util_hash_table_set(fd_tab, UINT_TO_PTR(fd), dev);
> +	util_hash_table_set(fd_tab, UINT_TO_PTR(dev->fd), dev);
>   	pthread_mutex_unlock(&fd_mutex);
>   
>   	return 0;
>   
>   cleanup:
> +	if (dev->fd)
> +		close(dev->fd);
>   	free(dev);
>   	pthread_mutex_unlock(&fd_mutex);
>   	return r;
> @@ -232,6 +235,9 @@ void amdgpu_device_free_internal(amdgpu_device_handle dev)
>   	pthread_mutex_destroy(&dev->bo_table_mutex);
>   	pthread_mutex_destroy(&(dev->vamgr.bo_va_mutex));
>   	util_hash_table_remove(fd_tab, UINT_TO_PTR(dev->fd));
> +	close(dev->fd);
> +	if (dev->fd != dev->flink_fd)
> +		close(dev->flink_fd);
>   	free(dev);
>   }
>