* [PATCH v2] Xen/atomic: use static inlines instead of macros
@ 2014-03-28 10:55 Andrew Cooper
2014-03-28 11:05 ` Jan Beulich
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Andrew Cooper @ 2014-03-28 10:55 UTC (permalink / raw)
To: Xen-devel
Cc: Keir Fraser, Ian Campbell, Andrew Cooper, Tim Deegan,
Stefano Stabellini, Jan Beulich
This is some coverity-inspired tidying.
Coverity has some grief analysing the call sites of atomic_read(). This is
believed to be a bug in Coverity itself when expanding the nested macros, but
there is no legitimate reason for it to be a macro in the first place.
This patch changes {,_}atomic_{read,set}() from being macros to being static
inline functions, thus gaining some type safety.
One issue which is not immediately obvious is that the non-atomic variants take
their atomic_t at a different level of indirection to the atomic variants.
This is not suitable for _atomic_set() (when used to initialise an atomic_t)
which is converted to take its parameter as a pointer. One callsite of
_atomic_set() is updated, while the other two callsites are updated to
ATOMIC_INIT().
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Keir Fraser <keir@xen.org>
CC: Jan Beulich <JBeulich@suse.com>
CC: Ian Campbell <ian.campbell@citrix.com>
CC: Stefano Stabellini <stefano.stabellini@citrix.com>
CC: Tim Deegan <tim@xen.org>
---
This is compile-tested on arm32 and 64, and functionally tested on x86_64
v2: spelling fixes in commit message, and remove some redundant brackets
---
xen/common/domain.c | 5 ++---
xen/include/asm-arm/atomic.h | 22 +++++++++++++++++----
xen/include/asm-x86/atomic.h | 43 +++++++++++++++++++++++++++++++++++-------
xen/include/xen/sched.h | 2 +-
4 files changed, 57 insertions(+), 15 deletions(-)
diff --git a/xen/common/domain.c b/xen/common/domain.c
index ad8a1b6..b414a7d 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -754,13 +754,12 @@ static void complete_domain_destroy(struct rcu_head *head)
void domain_destroy(struct domain *d)
{
struct domain **pd;
- atomic_t old, new;
+ atomic_t old = ATOMIC_INIT(0);
+ atomic_t new = ATOMIC_INIT(DOMAIN_DESTROYED);
BUG_ON(!d->is_dying);
/* May be already destroyed, or get_domain() can race us. */
- _atomic_set(old, 0);
- _atomic_set(new, DOMAIN_DESTROYED);
old = atomic_compareandswap(old, new, &d->refcnt);
if ( _atomic_read(old) != 0 )
return;
diff --git a/xen/include/asm-arm/atomic.h b/xen/include/asm-arm/atomic.h
index 69c8f3f..cb72547 100644
--- a/xen/include/asm-arm/atomic.h
+++ b/xen/include/asm-arm/atomic.h
@@ -83,11 +83,25 @@ typedef struct { int counter; } atomic_t;
* strex/ldrex monitor on some implementations. The reason we can use it for
* atomic_set() is the clrex or dummy strex done on every exception return.
*/
-#define _atomic_read(v) ((v).counter)
-#define atomic_read(v) (*(volatile int *)&(v)->counter)
+static inline int atomic_read(atomic_t *v)
+{
+ return *(volatile int *)&v->counter;
+}
+
+static inline int _atomic_read(atomic_t v)
+{
+ return v.counter;
+}
-#define _atomic_set(v,i) (((v).counter) = (i))
-#define atomic_set(v,i) (((v)->counter) = (i))
+static inline void atomic_set(atomic_t *v, int i)
+{
+ v->counter = i;
+}
+
+static inline void _atomic_set(atomic_t *v, int i)
+{
+ v->counter = i;
+}
#if defined(CONFIG_ARM_32)
# include <asm/arm32/atomic.h>
diff --git a/xen/include/asm-x86/atomic.h b/xen/include/asm-x86/atomic.h
index e476ab5..8972463 100644
--- a/xen/include/asm-x86/atomic.h
+++ b/xen/include/asm-x86/atomic.h
@@ -66,21 +66,50 @@ typedef struct { int counter; } atomic_t;
/**
* atomic_read - read atomic variable
* @v: pointer of type atomic_t
- *
+ *
* Atomically reads the value of @v.
*/
-#define _atomic_read(v) ((v).counter)
-#define atomic_read(v) read_atomic(&((v)->counter))
+static inline int atomic_read(atomic_t *v)
+{
+ return read_atomic(&v->counter);
+}
+
+/**
+ * _atomic_read - read atomic variable non-atomically
+ * @v atomic_t
+ *
+ * Non-atomically reads the value of @v
+ */
+static inline int _atomic_read(atomic_t v)
+{
+ return v.counter;
+}
+
/**
* atomic_set - set atomic variable
* @v: pointer of type atomic_t
* @i: required value
- *
+ *
* Atomically sets the value of @v to @i.
- */
-#define _atomic_set(v,i) (((v).counter) = (i))
-#define atomic_set(v,i) write_atomic(&((v)->counter), (i))
+ */
+static inline void atomic_set(atomic_t *v, int i)
+{
+ write_atomic(&v->counter, i);
+}
+
+/**
+ * _atomic_set - set atomic variable non-atomically
+ * @v: pointer of type atomic_t
+ * @i: required value
+ *
+ * Non-atomically sets the value of @v to @i.
+ */
+static inline void _atomic_set(atomic_t *v, int i)
+{
+ v->counter = i;
+}
+
/**
* atomic_add - add integer to atomic variable
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index b9ba379..92b4846 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -484,7 +484,7 @@ static always_inline int get_domain(struct domain *d)
old = seen;
if ( unlikely(_atomic_read(old) & DOMAIN_DESTROYED) )
return 0;
- _atomic_set(new, _atomic_read(old) + 1);
+ _atomic_set(&new, _atomic_read(old) + 1);
seen = atomic_compareandswap(old, new, &d->refcnt);
}
while ( unlikely(_atomic_read(seen) != _atomic_read(old)) );
--
1.7.10.4
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2] Xen/atomic: use static inlines instead of macros
2014-03-28 10:55 [PATCH v2] Xen/atomic: use static inlines instead of macros Andrew Cooper
@ 2014-03-28 11:05 ` Jan Beulich
2014-03-28 11:23 ` Andrew Cooper
2014-03-28 11:22 ` Tim Deegan
2014-04-01 10:11 ` Ian Campbell
2 siblings, 1 reply; 6+ messages in thread
From: Jan Beulich @ 2014-03-28 11:05 UTC (permalink / raw)
To: Andrew Cooper
Cc: Keir Fraser, Tim Deegan, StefanoStabellini, Ian Campbell, Xen-devel
>>> On 28.03.14 at 11:55, <andrew.cooper3@citrix.com> wrote:
> This is some coverity-inspired tidying.
>
> Coverity has some grief analysing the call sites of atomic_read(). This is
> believed to be a bug in Coverity itself when expanding the nested macros,
> but
> there is no legitimate reason for it to be a macro in the first place.
>
> This patch changes {,_}atomic_{read,set}() from being macros to being static
> inline functions, thus gaining some type safety.
>
> One issue which is not immediately obvious is that the non-atomic variants
> take
> their atomic_t at a different level of indirection to the atomic variants.
>
> This is not suitable for _atomic_set() (when used to initialise an atomic_t)
> which is converted to take its parameter as a pointer. One callsite of
> _atomic_set() is updated, while the other two callsites are updated to
> ATOMIC_INIT().
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> CC: Keir Fraser <keir@xen.org>
> CC: Jan Beulich <JBeulich@suse.com>
> CC: Ian Campbell <ian.campbell@citrix.com>
> CC: Stefano Stabellini <stefano.stabellini@citrix.com>
> CC: Tim Deegan <tim@xen.org>
>
> ---
>
> This is compile-tested on arm32 and 64, and functionally tested on x86_64
>
> v2: spelling fixes in commit message, and remove some redundant brackets
I see you left even the "non-atomic atomic ops" as inline functions,
other than suggested on v1. I'll leave it to Keir to decide whether
the resulting larger change is worthwhile the little benefit.
Jan
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] Xen/atomic: use static inlines instead of macros
2014-03-28 10:55 [PATCH v2] Xen/atomic: use static inlines instead of macros Andrew Cooper
2014-03-28 11:05 ` Jan Beulich
@ 2014-03-28 11:22 ` Tim Deegan
2014-04-01 10:39 ` Keir Fraser
2014-04-01 10:11 ` Ian Campbell
2 siblings, 1 reply; 6+ messages in thread
From: Tim Deegan @ 2014-03-28 11:22 UTC (permalink / raw)
To: Andrew Cooper
Cc: Stefano Stabellini, Keir Fraser, Ian Campbell, Jan Beulich, Xen-devel
At 10:55 +0000 on 28 Mar (1396000508), Andrew Cooper wrote:
> This is some coverity-inspired tidying.
>
> Coverity has some grief analysing the call sites of atomic_read(). This is
> believed to be a bug in Coverity itself when expanding the nested macros, but
> there is no legitimate reason for it to be a macro in the first place.
>
> This patch changes {,_}atomic_{read,set}() from being macros to being static
> inline functions, thus gaining some type safety.
>
> One issue which is not immediately obvious is that the non-atomic variants take
> their atomic_t at a different level of indirection to the atomic variants.
>
> This is not suitable for _atomic_set() (when used to initialise an atomic_t)
> which is converted to take its parameter as a pointer. One callsite of
> _atomic_set() is updated, while the other two callsites are updated to
> ATOMIC_INIT().
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Tim Deegan <tim@xen.org>
FWIW, I approve of converting both kinds of accessors to inlines, just
on general principles.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] Xen/atomic: use static inlines instead of macros
2014-03-28 11:05 ` Jan Beulich
@ 2014-03-28 11:23 ` Andrew Cooper
0 siblings, 0 replies; 6+ messages in thread
From: Andrew Cooper @ 2014-03-28 11:23 UTC (permalink / raw)
To: Jan Beulich
Cc: Keir Fraser, Tim Deegan, StefanoStabellini, Ian Campbell, Xen-devel
On 28/03/14 11:05, Jan Beulich wrote:
>>>> On 28.03.14 at 11:55, <andrew.cooper3@citrix.com> wrote:
>> This is some coverity-inspired tidying.
>>
>> Coverity has some grief analysing the call sites of atomic_read(). This is
>> believed to be a bug in Coverity itself when expanding the nested macros,
>> but
>> there is no legitimate reason for it to be a macro in the first place.
>>
>> This patch changes {,_}atomic_{read,set}() from being macros to being static
>> inline functions, thus gaining some type safety.
>>
>> One issue which is not immediately obvious is that the non-atomic variants
>> take
>> their atomic_t at a different level of indirection to the atomic variants.
>>
>> This is not suitable for _atomic_set() (when used to initialise an atomic_t)
>> which is converted to take its parameter as a pointer. One callsite of
>> _atomic_set() is updated, while the other two callsites are updated to
>> ATOMIC_INIT().
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>> CC: Keir Fraser <keir@xen.org>
>> CC: Jan Beulich <JBeulich@suse.com>
>> CC: Ian Campbell <ian.campbell@citrix.com>
>> CC: Stefano Stabellini <stefano.stabellini@citrix.com>
>> CC: Tim Deegan <tim@xen.org>
>>
>> ---
>>
>> This is compile-tested on arm32 and 64, and functionally tested on x86_64
>>
>> v2: spelling fixes in commit message, and remove some redundant brackets
> I see you left even the "non-atomic atomic ops" as inline functions,
> other than suggested on v1. I'll leave it to Keir to decide whether
> the resulting larger change is worthwhile the little benefit.
>
> Jan
>
I did explain why I disagreed with leaving the non-atomic as macros.
Any optimising compiler will generate the same code from either option,
but the static inline functions provide much more informative error
messages.
~Andrew
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] Xen/atomic: use static inlines instead of macros
2014-03-28 10:55 [PATCH v2] Xen/atomic: use static inlines instead of macros Andrew Cooper
2014-03-28 11:05 ` Jan Beulich
2014-03-28 11:22 ` Tim Deegan
@ 2014-04-01 10:11 ` Ian Campbell
2 siblings, 0 replies; 6+ messages in thread
From: Ian Campbell @ 2014-04-01 10:11 UTC (permalink / raw)
To: Andrew Cooper
Cc: Stefano Stabellini, Tim Deegan, Keir Fraser, Jan Beulich, Xen-devel
On Fri, 2014-03-28 at 10:55 +0000, Andrew Cooper wrote:
> This is some coverity-inspired tidying.
>
> Coverity has some grief analysing the call sites of atomic_read(). This is
> believed to be a bug in Coverity itself when expanding the nested macros, but
> there is no legitimate reason for it to be a macro in the first place.
>
> This patch changes {,_}atomic_{read,set}() from being macros to being static
> inline functions, thus gaining some type safety.
>
> One issue which is not immediately obvious is that the non-atomic variants take
> their atomic_t at a different level of indirection to the atomic variants.
>
> This is not suitable for _atomic_set() (when used to initialise an atomic_t)
> which is converted to take its parameter as a pointer. One callsite of
> _atomic_set() is updated, while the other two callsites are updated to
> ATOMIC_INIT().
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> CC: Keir Fraser <keir@xen.org>
> CC: Jan Beulich <JBeulich@suse.com>
For the arm bits:
Acked-by: Ian Campbell <ian.campbell@citrix.com>
I am assuming that someone else will be committing.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] Xen/atomic: use static inlines instead of macros
2014-03-28 11:22 ` Tim Deegan
@ 2014-04-01 10:39 ` Keir Fraser
0 siblings, 0 replies; 6+ messages in thread
From: Keir Fraser @ 2014-04-01 10:39 UTC (permalink / raw)
To: Tim Deegan
Cc: Keir Fraser, Ian Campbell, Andrew Cooper, Xen-devel,
Stefano Stabellini, Jan Beulich
[-- Attachment #1.1: Type: text/plain, Size: 1227 bytes --]
Tim Deegan wrote:
>
> At 10:55 +0000 on 28 Mar (1396000508), Andrew Cooper wrote:
>>
>> This is some coverity-inspired tidying.
>>
>> Coverity has some grief analysing the call sites of atomic_read().
>> This is
>> believed to be a bug in Coverity itself when expanding the nested
>> macros, but
>> there is no legitimate reason for it to be a macro in the first place.
>>
>> This patch changes {,_}atomic_{read,set}() from being macros to being
>> static
>> inline functions, thus gaining some type safety.
>>
>> One issue which is not immediately obvious is that the non-atomic
>> variants take
>> their atomic_t at a different level of indirection to the atomic
>> variants.
>>
>> This is not suitable for _atomic_set() (when used to initialise an
>> atomic_t)
>> which is converted to take its parameter as a pointer. One callsite of
>> _atomic_set() is updated, while the other two callsites are updated to
>> ATOMIC_INIT().
>>
>> Signed-off-by: Andrew Cooper<andrew.cooper3@citrix.com>
>
>
> Reviewed-by: Tim Deegan<tim@xen.org>
>
> FWIW, I approve of converting both kinds of accessors to inlines, just
> on general principles.
Agreed, functions are preferable to macros.
Acked-by: Keir Fraser <keir@xen.org>
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2014-03-28 10:55 [PATCH v2] Xen/atomic: use static inlines instead of macros Andrew Cooper
2014-03-28 11:05 ` Jan Beulich
2014-03-28 11:23 ` Andrew Cooper
2014-03-28 11:22 ` Tim Deegan
2014-04-01 10:39 ` Keir Fraser
2014-04-01 10:11 ` Ian Campbell
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