[PATCH 0/2 v3] Add cond_guard() to conditional guards

[PATCH 0/2 v3] Add cond_guard() to conditional guards

[Fabio M. De Francesco]

Add cond_guard() macro to conditional guards and use it to replace an
open-coded up_read() in show_targetN() and remove a block marked by an
'out' label.

Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>
---

Changes from RFC v4:
        Changed the interface of cond_guard() to take a variable to store
        a return code, the succes code and failure code, to enable a
        later check of the returned code in that variable.
Changes from RFC v5:
        Changed the interface of cond_guard() to take a statement or 
	statement-expression as its second argument to conform to Dan's 
	suggestion (thanks).
Changes from v1:
        Fixed a grammar error in the commit message of 1/2; replaced the
        name of the second argument of cond_guard() with '_fail'
        according to Jonathan's comments (thanks). 
Changes from v2:
	Changed macro's implementation to add an 'else' to protect
	against it being used incorrectly within another if() block.
	Suggested by Dan (thanks). The Reviewed-by tags on 1/2 are not
	forwarded because the implementation of cond_guard() has changed.
	Removed a redundant 'else' from show_targetN() in 2/2.

Fabio M. De Francesco (2):
  cleanup: Add cond_guard() to conditional guards
  cxl/region: Use cond_guard() in show_targetN()

 drivers/cxl/core/region.c | 16 ++++------------
 include/linux/cleanup.h   | 15 +++++++++++++++
 2 files changed, 19 insertions(+), 12 deletions(-)

-- 
2.43.0

[PATCH 1/2 v3] cleanup: Add cond_guard() to conditional guards

[Fabio M. De Francesco]

Add cond_guard() macro to conditional guards.

cond_guard() is a guard to be used with the conditional variants of locks,
like down_read_trylock() or mutex_lock_interruptible().

It takes a statement (or statement-expression) that is passed as its
second argument. That statement (or statement-expression) is executed if
waiting for a lock is interrupted or if a _trylock() fails in case of
contention.

Usage example:

	cond_guard(mutex_intr, return -EINTR, &mutex);

Consistent with other usage of _guard(), locks are unlocked at the exit of the
scope where cond_guard() is called.

Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>
---
 include/linux/cleanup.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
index c2d09bc4f976..d70454e9f8dc 100644
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -134,6 +134,16 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
  *	an anonymous instance of the (guard) class, not recommended for
  *	conditional locks.
  *
+ * cond_guard(name, fail, args...):
+ *	a guard to be used with the conditional variants of locks, like
+ *	down_read_trylock() or mutex_lock_interruptible. 'fail' is a
+ *	statement or statement-expression that is executed if waiting for a
+ *	lock is interrupted or if a _trylock() fails in case of contention.
+ *
+ *	Example:
+ *
+ *		cond_guard(mutex_intr, return -EINTR, &mutex);
+ *
  * scoped_guard (name, args...) { }:
  *	similar to CLASS(name, scope)(args), except the variable (with the
  *	explicit name 'scope') is declard in a for-loop such that its scope is
@@ -165,6 +175,11 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
 
 #define __guard_ptr(_name) class_##_name##_lock_ptr
 
+#define cond_guard(_name, _fail, args...) \
+	CLASS(_name, scope)(args); \
+	if (!__guard_ptr(_name)(&scope)) _fail; \
+	else
+
 #define scoped_guard(_name, args...)					\
 	for (CLASS(_name, scope)(args),					\
 	     *done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)
-- 
2.43.0

Re: [PATCH 1/2 v3] cleanup: Add cond_guard() to conditional guards

[Ira Weiny]

Fabio M. De Francesco wrote:
> Add cond_guard() macro to conditional guards.
> 
> cond_guard() is a guard to be used with the conditional variants of locks,
> like down_read_trylock() or mutex_lock_interruptible().
> 
> It takes a statement (or statement-expression) that is passed as its
> second argument. That statement (or statement-expression) is executed if
> waiting for a lock is interrupted or if a _trylock() fails in case of
> contention.
> 
> Usage example:
> 
> 	cond_guard(mutex_intr, return -EINTR, &mutex);
> 
> Consistent with other usage of _guard(), locks are unlocked at the exit of the
> scope where cond_guard() is called.
> 
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Suggested-by: Ira Weiny <ira.weiny@intel.com>

Thanks for the revisions!

Reviewed-by: Ira Weiny <ira.weiny@intel.com>

Re: [PATCH 1/2 v3] cleanup: Add cond_guard() to conditional guards

[Dave Jiang]

On 2/6/24 5:13 AM, Fabio M. De Francesco wrote:
> Add cond_guard() macro to conditional guards.
> 
> cond_guard() is a guard to be used with the conditional variants of locks,
> like down_read_trylock() or mutex_lock_interruptible().
> 
> It takes a statement (or statement-expression) that is passed as its
> second argument. That statement (or statement-expression) is executed if
> waiting for a lock is interrupted or if a _trylock() fails in case of
> contention.
> 
> Usage example:
> 
> 	cond_guard(mutex_intr, return -EINTR, &mutex);
> 
> Consistent with other usage of _guard(), locks are unlocked at the exit of the
> scope where cond_guard() is called.
> 
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Suggested-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> ---
>  include/linux/cleanup.h | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
> index c2d09bc4f976..d70454e9f8dc 100644
> --- a/include/linux/cleanup.h
> +++ b/include/linux/cleanup.h
> @@ -134,6 +134,16 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
>   *	an anonymous instance of the (guard) class, not recommended for
>   *	conditional locks.
>   *
> + * cond_guard(name, fail, args...):
> + *	a guard to be used with the conditional variants of locks, like
> + *	down_read_trylock() or mutex_lock_interruptible. 'fail' is a
> + *	statement or statement-expression that is executed if waiting for a
> + *	lock is interrupted or if a _trylock() fails in case of contention.
> + *
> + *	Example:
> + *
> + *		cond_guard(mutex_intr, return -EINTR, &mutex);
> + *
>   * scoped_guard (name, args...) { }:
>   *	similar to CLASS(name, scope)(args), except the variable (with the
>   *	explicit name 'scope') is declard in a for-loop such that its scope is
> @@ -165,6 +175,11 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
>  
>  #define __guard_ptr(_name) class_##_name##_lock_ptr
>  
> +#define cond_guard(_name, _fail, args...) \
> +	CLASS(_name, scope)(args); \
> +	if (!__guard_ptr(_name)(&scope)) _fail; \
> +	else
> +
>  #define scoped_guard(_name, args...)					\
>  	for (CLASS(_name, scope)(args),					\
>  	     *done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)

[PATCH 2/2 v3] cxl/region: Use cond_guard() in show_targetN()

[Fabio M. De Francesco]

Use cond_guard() in show_target() to not open code an up_read() in an 'out'
block. If the down_read_interruptible() fails, the statement passed to the
second argument of cond_guard() returns -EINTR.

Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>
---
 drivers/cxl/core/region.c | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 0f05692bfec3..eb5c36462c0a 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -666,28 +666,20 @@ static size_t show_targetN(struct cxl_region *cxlr, char *buf, int pos)
 {
 	struct cxl_region_params *p = &cxlr->params;
 	struct cxl_endpoint_decoder *cxled;
-	int rc;
 
-	rc = down_read_interruptible(&cxl_region_rwsem);
-	if (rc)
-		return rc;
+	cond_guard(rwsem_read_intr, return -EINTR, &cxl_region_rwsem);
 
 	if (pos >= p->interleave_ways) {
 		dev_dbg(&cxlr->dev, "position %d out of range %d\n", pos,
 			p->interleave_ways);
-		rc = -ENXIO;
-		goto out;
+		return -ENXIO;
 	}
 
 	cxled = p->targets[pos];
 	if (!cxled)
-		rc = sysfs_emit(buf, "\n");
-	else
-		rc = sysfs_emit(buf, "%s\n", dev_name(&cxled->cxld.dev));
-out:
-	up_read(&cxl_region_rwsem);
+		return sysfs_emit(buf, "\n");
 
-	return rc;
+	return sysfs_emit(buf, "%s\n", dev_name(&cxled->cxld.dev));
 }
 
 static int match_free_decoder(struct device *dev, void *data)
-- 
2.43.0

Re: [PATCH 2/2 v3] cxl/region: Use cond_guard() in show_targetN()

[Dave Jiang]

On 2/6/24 5:13 AM, Fabio M. De Francesco wrote:
> Use cond_guard() in show_target() to not open code an up_read() in an 'out'
> block. If the down_read_interruptible() fails, the statement passed to the
> second argument of cond_guard() returns -EINTR.
> 
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Suggested-by: Ira Weiny <ira.weiny@intel.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Reviewed-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Fabio M. De Francesco <fabio.maria.de.francesco@linux.intel.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> ---
>  drivers/cxl/core/region.c | 16 ++++------------
>  1 file changed, 4 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 0f05692bfec3..eb5c36462c0a 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -666,28 +666,20 @@ static size_t show_targetN(struct cxl_region *cxlr, char *buf, int pos)
>  {
>  	struct cxl_region_params *p = &cxlr->params;
>  	struct cxl_endpoint_decoder *cxled;
> -	int rc;
>  
> -	rc = down_read_interruptible(&cxl_region_rwsem);
> -	if (rc)
> -		return rc;
> +	cond_guard(rwsem_read_intr, return -EINTR, &cxl_region_rwsem);
>  
>  	if (pos >= p->interleave_ways) {
>  		dev_dbg(&cxlr->dev, "position %d out of range %d\n", pos,
>  			p->interleave_ways);
> -		rc = -ENXIO;
> -		goto out;
> +		return -ENXIO;
>  	}
>  
>  	cxled = p->targets[pos];
>  	if (!cxled)
> -		rc = sysfs_emit(buf, "\n");
> -	else
> -		rc = sysfs_emit(buf, "%s\n", dev_name(&cxled->cxld.dev));
> -out:
> -	up_read(&cxl_region_rwsem);
> +		return sysfs_emit(buf, "\n");
>  
> -	return rc;
> +	return sysfs_emit(buf, "%s\n", dev_name(&cxled->cxld.dev));
>  }
>  
>  static int match_free_decoder(struct device *dev, void *data)

Re: [PATCH 2/2 v3] cxl/region: Use cond_guard() in show_targetN()

[kernel test robot]

Hi Fabio,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on v6.8-rc3 next-20240206]
[cannot apply to cxl/next cxl/pending]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Fabio-M-De-Francesco/cleanup-Add-cond_guard-to-conditional-guards/20240206-203110
base:   linus/master
patch link:    https://lore.kernel.org/r/20240206121301.7225-3-fabio.maria.de.francesco%40linux.intel.com
patch subject: [PATCH 2/2 v3] cxl/region: Use cond_guard() in show_targetN()
config: s390-allyesconfig (https://download.01.org/0day-ci/archive/20240207/202402070919.0zuYCxMS-lkp@intel.com/config)
compiler: s390-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240207/202402070919.0zuYCxMS-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202402070919.0zuYCxMS-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/cxl/core/region.c: In function 'show_targetN':
>> drivers/cxl/core/region.c:670:70: warning: suggest braces around empty body in an 'else' statement [-Wempty-body]
     670 |         cond_guard(rwsem_read_intr, return -EINTR, &cxl_region_rwsem);
         |                                                                      ^


vim +/else +670 drivers/cxl/core/region.c

   664	
   665	static size_t show_targetN(struct cxl_region *cxlr, char *buf, int pos)
   666	{
   667		struct cxl_region_params *p = &cxlr->params;
   668		struct cxl_endpoint_decoder *cxled;
   669	
 > 670		cond_guard(rwsem_read_intr, return -EINTR, &cxl_region_rwsem);
   671	
   672		if (pos >= p->interleave_ways) {
   673			dev_dbg(&cxlr->dev, "position %d out of range %d\n", pos,
   674				p->interleave_ways);
   675			return -ENXIO;
   676		}
   677	
   678		cxled = p->targets[pos];
   679		if (!cxled)
   680			return sysfs_emit(buf, "\n");
   681	
   682		return sysfs_emit(buf, "%s\n", dev_name(&cxled->cxld.dev));
   683	}
   684	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH 2/2 v3] cxl/region: Use cond_guard() in show_targetN()

[Fabio M. De Francesco]

On Wednesday, 7 February 2024 02:54:34 CET kernel test robot wrote:
> Hi Fabio,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on linus/master]
> [also build test WARNING on v6.8-rc3 next-20240206]
> [cannot apply to cxl/next cxl/pending]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
> 
> url:   
> https://github.com/intel-lab-lkp/linux/commits/Fabio-M-De-Francesco/cleanup
> -Add-cond_guard-to-conditional-guards/20240206-203110 base:   linus/master
> patch link:   
> https://lore.kernel.org/r/20240206121301.7225-3-fabio.maria.de.francesco%40
> linux.intel.com patch subject: [PATCH 2/2 v3] cxl/region: Use cond_guard()
> in show_targetN() config: s390-allyesconfig
> (https://download.01.org/0day-ci/archive/20240207/202402070919.0zuYCxMS-lkp
> @intel.com/config) compiler: s390-linux-gcc (GCC) 13.2.0
> reproduce (this is a W=1 build):
> (https://download.01.org/0day-ci/archive/20240207/202402070919.0zuYCxMS-lkp
> @intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version
> of the same patch/commit), kindly add following tags
> 
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes:
> | https://lore.kernel.org/oe-kbuild-all/202402070919.0zuYCxMS-lkp@intel.com
> | /
> All warnings (new ones prefixed by >>):
> 
>    drivers/cxl/core/region.c: In function 'show_targetN':
> >> drivers/cxl/core/region.c:670:70: warning: suggest braces around empty
> >> body in an 'else' statement [-Wempty-body]
>      670 |         cond_guard(rwsem_read_intr, return -EINTR,
> &cxl_region_rwsem);
>          |                                                                      
^

I think that this warning deserves attention and braces should be added around 
the 'else' empty body. I'm going to send v4:

#define cond_guard(_name, _ret, args...) \
        CLASS(_name, scope)(args); \
        if (!__guard_ptr(_name)(&scope)) _ret; \
        else { }

Any comments?

Fabio

> 
> vim +/else +670 drivers/cxl/core/region.c
> 
>    664
>    665	static size_t show_targetN(struct cxl_region *cxlr, char *buf, int
> pos) 666	{
>    667		struct cxl_region_params *p = &cxlr->params;
>    668		struct cxl_endpoint_decoder *cxled;
>    669
> 
>  > 670		cond_guard(rwsem_read_intr, return -EINTR, 
&cxl_region_rwsem);
> 
>    671
>    672		if (pos >= p->interleave_ways) {
>    673			dev_dbg(&cxlr->dev, "position %d out of range 
%d\n", pos,
>    674				p->interleave_ways);
>    675			return -ENXIO;
>    676		}
>    677
>    678		cxled = p->targets[pos];
>    679		if (!cxled)
>    680			return sysfs_emit(buf, "\n");
>    681
>    682		return sysfs_emit(buf, "%s\n", dev_name(&cxled-
>cxld.dev));
>    683	}
>    684

Re: [PATCH 2/2 v3] cxl/region: Use cond_guard() in show_targetN()

[Ira Weiny]

Fabio M. De Francesco wrote:
> On Wednesday, 7 February 2024 02:54:34 CET kernel test robot wrote:
> > Hi Fabio,
> > 
> > kernel test robot noticed the following build warnings:
> > 
> > [auto build test WARNING on linus/master]
> > [also build test WARNING on v6.8-rc3 next-20240206]
> > [cannot apply to cxl/next cxl/pending]
> > [If your patch is applied to the wrong git tree, kindly drop us a note.
> > And when submitting patch, we suggest to use '--base' as documented in
> > https://git-scm.com/docs/git-format-patch#_base_tree_information]
> > 
> > url:   
> > https://github.com/intel-lab-lkp/linux/commits/Fabio-M-De-Francesco/cleanup
> > -Add-cond_guard-to-conditional-guards/20240206-203110 base:   linus/master
> > patch link:   
> > https://lore.kernel.org/r/20240206121301.7225-3-fabio.maria.de.francesco%40
> > linux.intel.com patch subject: [PATCH 2/2 v3] cxl/region: Use cond_guard()
> > in show_targetN() config: s390-allyesconfig
> > (https://download.01.org/0day-ci/archive/20240207/202402070919.0zuYCxMS-lkp
> > @intel.com/config) compiler: s390-linux-gcc (GCC) 13.2.0
> > reproduce (this is a W=1 build):
> > (https://download.01.org/0day-ci/archive/20240207/202402070919.0zuYCxMS-lkp
> > @intel.com/reproduce)
> > 
> > If you fix the issue in a separate patch/commit (i.e. not just a new version
> > of the same patch/commit), kindly add following tags
> > 
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Closes:
> > | https://lore.kernel.org/oe-kbuild-all/202402070919.0zuYCxMS-lkp@intel.com
> > | /
> > All warnings (new ones prefixed by >>):
> > 
> >    drivers/cxl/core/region.c: In function 'show_targetN':
> > >> drivers/cxl/core/region.c:670:70: warning: suggest braces around empty
> > >> body in an 'else' statement [-Wempty-body]
> >      670 |         cond_guard(rwsem_read_intr, return -EINTR,
> > &cxl_region_rwsem);
> >          |                                                                      
> ^
> 
> I think that this warning deserves attention and braces should be added around 
> the 'else' empty body. I'm going to send v4:
> 
> #define cond_guard(_name, _ret, args...) \
>         CLASS(_name, scope)(args); \
>         if (!__guard_ptr(_name)(&scope)) _ret; \
>         else { }
>

I think this is a good addition.  If the user forgets ';' at the end of
the cond_guard() we could have a hidden side effect similar to what Dan
was concerned about...  This guarantees that won't happen.

Score one for the bots!
Ira