Re: [Intel-gfx] [PATCH] drm/i915: Ditch the i915_gem_ww_ctx loop member
On 8/16/21 3:34 PM, Maarten Lankhorst wrote:
Op 16-08-2021 om 15:30 schreef Thomas Hellström:
On 8/16/21 3:25 PM, Matthew Auld wrote:
On Mon, 16 Aug 2021 at 09:49, Thomas Hellström
wrote:
It's only used by the for_i915_gem_ww() macro and we can use
the (typically) on-stack _err variable in its place.
While initially setting the _err variable to -EDEADLK to enter the
loop, we clear it before actually entering using fetch_and_zero() to
avoid empty loops or code not setting the _err variable running forever.
Suggested-by: Maarten Lankhorst
Signed-off-by: Thomas Hellström
---
drivers/gpu/drm/i915/i915_gem_ww.h | 23 ---
1 file changed, 8 insertions(+), 15 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_ww.h
b/drivers/gpu/drm/i915/i915_gem_ww.h
index f6b1a796667b..98348b1e6182 100644
--- a/drivers/gpu/drm/i915/i915_gem_ww.h
+++ b/drivers/gpu/drm/i915/i915_gem_ww.h
@@ -7,12 +7,13 @@
#include
+#include "i915_utils.h"
+
struct i915_gem_ww_ctx {
struct ww_acquire_ctx ctx;
struct list_head obj_list;
struct drm_i915_gem_object *contended;
- unsigned short intr;
- unsigned short loop;
+ bool intr;
};
void i915_gem_ww_ctx_init(struct i915_gem_ww_ctx *ctx, bool intr);
@@ -23,28 +24,20 @@ void i915_gem_ww_unlock_single(struct drm_i915_gem_object
*obj);
/* Internal functions used by the inlines! Don't use. */
static inline int __i915_gem_ww_fini(struct i915_gem_ww_ctx *ww, int err)
{
- ww->loop = 0;
if (err == -EDEADLK) {
err = i915_gem_ww_ctx_backoff(ww);
if (!err)
- ww->loop = 1;
+ err = -EDEADLK;
}
- if (!ww->loop)
+ if (err != -EDEADLK)
i915_gem_ww_ctx_fini(ww);
return err;
}
-static inline void
-__i915_gem_ww_init(struct i915_gem_ww_ctx *ww, bool intr)
-{
- i915_gem_ww_ctx_init(ww, intr);
- ww->loop = 1;
-}
-
-#define for_i915_gem_ww(_ww, _err, _intr) \
- for (__i915_gem_ww_init(_ww, _intr); (_ww)->loop; \
+#define for_i915_gem_ww(_ww, _err, _intr) \
+ for (i915_gem_ww_ctx_init(_ww, _intr), (_err) = -EDEADLK; \
+ fetch_and_zero(&_err) == -EDEADLK; \
Doesn't this now hide "normal" errors, like say get_pages() returning
-ENOSPC or so?
Yes, good catch. We should either just clear the -EDEADLK case, or not clear
the error at all..
/Thomas
I believe not setting _err is a bug anyway. Why would you do such a loop without at
least one err = ww_mutex_lock(&ww); ?
Infinite loop would catch that at first test.
OK, I'll skip the clearing then.
/Thomas
~Maarten
Re: [Intel-gfx] [PATCH] drm/i915: Ditch the i915_gem_ww_ctx loop member
Op 16-08-2021 om 15:30 schreef Thomas Hellström:
>
> On 8/16/21 3:25 PM, Matthew Auld wrote:
>> On Mon, 16 Aug 2021 at 09:49, Thomas Hellström
>> wrote:
>>> It's only used by the for_i915_gem_ww() macro and we can use
>>> the (typically) on-stack _err variable in its place.
>>>
>>> While initially setting the _err variable to -EDEADLK to enter the
>>> loop, we clear it before actually entering using fetch_and_zero() to
>>> avoid empty loops or code not setting the _err variable running forever.
>>>
>>> Suggested-by: Maarten Lankhorst
>>> Signed-off-by: Thomas Hellström
>>> ---
>>> drivers/gpu/drm/i915/i915_gem_ww.h | 23 ---
>>> 1 file changed, 8 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_gem_ww.h
>>> b/drivers/gpu/drm/i915/i915_gem_ww.h
>>> index f6b1a796667b..98348b1e6182 100644
>>> --- a/drivers/gpu/drm/i915/i915_gem_ww.h
>>> +++ b/drivers/gpu/drm/i915/i915_gem_ww.h
>>> @@ -7,12 +7,13 @@
>>>
>>> #include
>>>
>>> +#include "i915_utils.h"
>>> +
>>> struct i915_gem_ww_ctx {
>>> struct ww_acquire_ctx ctx;
>>> struct list_head obj_list;
>>> struct drm_i915_gem_object *contended;
>>> - unsigned short intr;
>>> - unsigned short loop;
>>> + bool intr;
>>> };
>>>
>>> void i915_gem_ww_ctx_init(struct i915_gem_ww_ctx *ctx, bool intr);
>>> @@ -23,28 +24,20 @@ void i915_gem_ww_unlock_single(struct
>>> drm_i915_gem_object *obj);
>>> /* Internal functions used by the inlines! Don't use. */
>>> static inline int __i915_gem_ww_fini(struct i915_gem_ww_ctx *ww, int err)
>>> {
>>> - ww->loop = 0;
>>> if (err == -EDEADLK) {
>>> err = i915_gem_ww_ctx_backoff(ww);
>>> if (!err)
>>> - ww->loop = 1;
>>> + err = -EDEADLK;
>>> }
>>>
>>> - if (!ww->loop)
>>> + if (err != -EDEADLK)
>>> i915_gem_ww_ctx_fini(ww);
>>>
>>> return err;
>>> }
>>>
>>> -static inline void
>>> -__i915_gem_ww_init(struct i915_gem_ww_ctx *ww, bool intr)
>>> -{
>>> - i915_gem_ww_ctx_init(ww, intr);
>>> - ww->loop = 1;
>>> -}
>>> -
>>> -#define for_i915_gem_ww(_ww, _err, _intr) \
>>> - for (__i915_gem_ww_init(_ww, _intr); (_ww)->loop; \
>>> +#define for_i915_gem_ww(_ww, _err, _intr) \
>>> + for (i915_gem_ww_ctx_init(_ww, _intr), (_err) = -EDEADLK; \
>>> + fetch_and_zero(&_err) == -EDEADLK; \
>> Doesn't this now hide "normal" errors, like say get_pages() returning
>> -ENOSPC or so?
>
> Yes, good catch. We should either just clear the -EDEADLK case, or not clear
> the error at all..
>
> /Thomas
I believe not setting _err is a bug anyway. Why would you do such a loop
without at least one err = ww_mutex_lock(&ww); ?
Infinite loop would catch that at first test.
~Maarten
Re: [Intel-gfx] [PATCH] drm/i915: Ditch the i915_gem_ww_ctx loop member
On 8/16/21 3:25 PM, Matthew Auld wrote:
On Mon, 16 Aug 2021 at 09:49, Thomas Hellström
wrote:
It's only used by the for_i915_gem_ww() macro and we can use
the (typically) on-stack _err variable in its place.
While initially setting the _err variable to -EDEADLK to enter the
loop, we clear it before actually entering using fetch_and_zero() to
avoid empty loops or code not setting the _err variable running forever.
Suggested-by: Maarten Lankhorst
Signed-off-by: Thomas Hellström
---
drivers/gpu/drm/i915/i915_gem_ww.h | 23 ---
1 file changed, 8 insertions(+), 15 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_ww.h
b/drivers/gpu/drm/i915/i915_gem_ww.h
index f6b1a796667b..98348b1e6182 100644
--- a/drivers/gpu/drm/i915/i915_gem_ww.h
+++ b/drivers/gpu/drm/i915/i915_gem_ww.h
@@ -7,12 +7,13 @@
#include
+#include "i915_utils.h"
+
struct i915_gem_ww_ctx {
struct ww_acquire_ctx ctx;
struct list_head obj_list;
struct drm_i915_gem_object *contended;
- unsigned short intr;
- unsigned short loop;
+ bool intr;
};
void i915_gem_ww_ctx_init(struct i915_gem_ww_ctx *ctx, bool intr);
@@ -23,28 +24,20 @@ void i915_gem_ww_unlock_single(struct drm_i915_gem_object
*obj);
/* Internal functions used by the inlines! Don't use. */
static inline int __i915_gem_ww_fini(struct i915_gem_ww_ctx *ww, int err)
{
- ww->loop = 0;
if (err == -EDEADLK) {
err = i915_gem_ww_ctx_backoff(ww);
if (!err)
- ww->loop = 1;
+ err = -EDEADLK;
}
- if (!ww->loop)
+ if (err != -EDEADLK)
i915_gem_ww_ctx_fini(ww);
return err;
}
-static inline void
-__i915_gem_ww_init(struct i915_gem_ww_ctx *ww, bool intr)
-{
- i915_gem_ww_ctx_init(ww, intr);
- ww->loop = 1;
-}
-
-#define for_i915_gem_ww(_ww, _err, _intr) \
- for (__i915_gem_ww_init(_ww, _intr); (_ww)->loop; \
+#define for_i915_gem_ww(_ww, _err, _intr)\
+ for (i915_gem_ww_ctx_init(_ww, _intr), (_err) = -EDEADLK; \
+fetch_and_zero(&_err) == -EDEADLK; \
Doesn't this now hide "normal" errors, like say get_pages() returning
-ENOSPC or so?
Yes, good catch. We should either just clear the -EDEADLK case, or not
clear the error at all..
/Thomas
Re: [Intel-gfx] [PATCH] drm/i915: Ditch the i915_gem_ww_ctx loop member
On Mon, 16 Aug 2021 at 09:49, Thomas Hellström
wrote:
>
> It's only used by the for_i915_gem_ww() macro and we can use
> the (typically) on-stack _err variable in its place.
>
> While initially setting the _err variable to -EDEADLK to enter the
> loop, we clear it before actually entering using fetch_and_zero() to
> avoid empty loops or code not setting the _err variable running forever.
>
> Suggested-by: Maarten Lankhorst
> Signed-off-by: Thomas Hellström
> ---
> drivers/gpu/drm/i915/i915_gem_ww.h | 23 ---
> 1 file changed, 8 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_ww.h
> b/drivers/gpu/drm/i915/i915_gem_ww.h
> index f6b1a796667b..98348b1e6182 100644
> --- a/drivers/gpu/drm/i915/i915_gem_ww.h
> +++ b/drivers/gpu/drm/i915/i915_gem_ww.h
> @@ -7,12 +7,13 @@
>
> #include
>
> +#include "i915_utils.h"
> +
> struct i915_gem_ww_ctx {
> struct ww_acquire_ctx ctx;
> struct list_head obj_list;
> struct drm_i915_gem_object *contended;
> - unsigned short intr;
> - unsigned short loop;
> + bool intr;
> };
>
> void i915_gem_ww_ctx_init(struct i915_gem_ww_ctx *ctx, bool intr);
> @@ -23,28 +24,20 @@ void i915_gem_ww_unlock_single(struct drm_i915_gem_object
> *obj);
> /* Internal functions used by the inlines! Don't use. */
> static inline int __i915_gem_ww_fini(struct i915_gem_ww_ctx *ww, int err)
> {
> - ww->loop = 0;
> if (err == -EDEADLK) {
> err = i915_gem_ww_ctx_backoff(ww);
> if (!err)
> - ww->loop = 1;
> + err = -EDEADLK;
> }
>
> - if (!ww->loop)
> + if (err != -EDEADLK)
> i915_gem_ww_ctx_fini(ww);
>
> return err;
> }
>
> -static inline void
> -__i915_gem_ww_init(struct i915_gem_ww_ctx *ww, bool intr)
> -{
> - i915_gem_ww_ctx_init(ww, intr);
> - ww->loop = 1;
> -}
> -
> -#define for_i915_gem_ww(_ww, _err, _intr) \
> - for (__i915_gem_ww_init(_ww, _intr); (_ww)->loop; \
> +#define for_i915_gem_ww(_ww, _err, _intr)\
> + for (i915_gem_ww_ctx_init(_ww, _intr), (_err) = -EDEADLK; \
> +fetch_and_zero(&_err) == -EDEADLK; \
Doesn't this now hide "normal" errors, like say get_pages() returning
-ENOSPC or so?
> _err = __i915_gem_ww_fini(_ww, _err))
> -
> #endif
> --
> 2.31.1
>
