Re: [PATCH v2 03/11] locking/ww_mutex: Extract stamp comparison to __ww_mutex_stamp_after

[Chris Wilson]

On Thu, Dec 01, 2016 at 03:06:46PM +0100, Nicolai Hähnle wrote:
> From: Nicolai Hähnle 
> 
> The function will be re-used in subsequent patches.
> 
> Cc: Peter Zijlstra 
> Cc: Ingo Molnar 
> Cc: Maarten Lankhorst 
> Cc: Daniel Vetter 
> Cc: Chris Wilson 
> Cc: dri-de...@lists.freedesktop.org
> Signed-off-by: Nicolai Hähnle 
> ---
>  kernel/locking/mutex.c | 10 --
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
> index 0afa998..200629a 100644
> --- a/kernel/locking/mutex.c
> +++ b/kernel/locking/mutex.c
> @@ -277,6 +277,13 @@ static __always_inline void 
> ww_mutex_lock_acquired(struct ww_mutex *ww,
>   ww_ctx->acquired++;
>  }
>  
> +static inline bool __sched
> +__ww_mutex_stamp_after(struct ww_acquire_ctx *a, struct ww_acquire_ctx *b)

Should it be ww_mutex_stamp or ww_acquire_stamp / ww_ctx_stamp?

Nothing else operates on the ww_acquire_ctx without a ww_mutex so it
might look a bit odd if it didn't use ww_mutex.

Patch only does what it says on tin, so
Reviewed-by: Chris Wilson 
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre

[PATCH v2 03/11] locking/ww_mutex: Extract stamp comparison to __ww_mutex_stamp_after

[Nicolai Hähnle]

From: Nicolai Hähnle 

The function will be re-used in subsequent patches.

Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Maarten Lankhorst 
Cc: Daniel Vetter 
Cc: Chris Wilson 
Cc: dri-de...@lists.freedesktop.org
Signed-off-by: Nicolai Hähnle 
---
 kernel/locking/mutex.c | 10 --
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index 0afa998..200629a 100644
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -277,6 +277,13 @@ static __always_inline void ww_mutex_lock_acquired(struct 
ww_mutex *ww,
ww_ctx->acquired++;
 }
 
+static inline bool __sched
+__ww_mutex_stamp_after(struct ww_acquire_ctx *a, struct ww_acquire_ctx *b)
+{
+   return a->stamp - b->stamp <= LONG_MAX &&
+  (a->stamp != b->stamp || a > b);
+}
+
 /*
  * After acquiring lock with fastpath or when we lost out in contested
  * slowpath, set ctx and wake up any waiters so they can recheck.
@@ -610,8 +617,7 @@ __ww_mutex_lock_check_stamp(struct mutex *lock, struct 
ww_acquire_ctx *ctx)
if (!hold_ctx)
return 0;
 
-   if (ctx->stamp - hold_ctx->stamp <= LONG_MAX &&
-   (ctx->stamp != hold_ctx->stamp || ctx > hold_ctx)) {
+   if (__ww_mutex_stamp_after(ctx, hold_ctx)) {
 #ifdef CONFIG_DEBUG_MUTEXES
DEBUG_LOCKS_WARN_ON(ctx->contending_lock);
ctx->contending_lock = ww;
-- 
2.7.4