On 10/18/24 13:15, Peter Zijlstra wrote:
On Tue, Oct 01, 2024 at 05:30:18PM -0500, David Lechner wrote:
Add a new if_not_cond_guard() macro to cleanup.h for handling
conditional guards such as mutext_trylock().
This is more ergonomic than scoped_cond_guard() for most use cases.
Instead of hiding the error handling statement in the macro args, it
works like a normal if statement and allow the error path to be indented
while the normal code flow path is not indented. And it avoid unwanted
side-effect from hidden for loop in scoped_cond_guard().
Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx>
So this is guard()() with error handler for cond class of locks.
I would name such guard_or_err(), or guard_or_err_block(), to make it
obvious why there is a block attached (so bad we could not ENFORCE that
there is a block atached).
Then, having it, it would make sense to not only limit guard_or_err() to
cond class of locks, but also forbid plain guard() with cond locks
(instead just discouraging it in the doc).
---
include/linux/cleanup.h | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
index 038b2d523bf8..682bb3fadfc9 100644
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -273,6 +273,10 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
* an anonymous instance of the (guard) class, not recommended for
* conditional locks.
*
+ * if_not_cond_guard(name, args...) { <error handling> }:
+ * convenience macro for conditional guards that calls the statement that
+ * follows only if the lock was not acquired (typically an error return).
+ *
* 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
@@ -304,6 +308,13 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
#define __guard_ptr(_name) class_##_name##_lock_ptr
+#define __if_not_cond_guard(_name, _id, args...) \
+ CLASS(_name, _id)(args); \
+ if (!__guard_ptr(_name)(&_id))
+
+#define if_not_cond_guard(_name, args...) \
+ __if_not_cond_guard(_name, __UNIQUE_ID(guard), args)
+
#define scoped_guard(_name, args...) \
for (CLASS(_name, scope)(args), \
*done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)
So if I stick this on top of:
https://lkml.kernel.org/r/20241011121535.28049-1-przemyslaw.kitszel@xxxxxxxxx
I have v4 that fixes non-cond version. Apologies it took me that long.
[v4]
https://lore.kernel.org/netdev/20241018113823.171256-1-przemyslaw.kitszel@xxxxxxxxx
I have tested it also with the unrechable() calls removed, as suggested
by David Lechner here:
https://lore.kernel.org/netdev/0f4786e9-d738-435d-afb9-8c0c4a028ddb@xxxxxxxxxxxx
then I can add the below:
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -277,6 +277,8 @@ static inline class_##_name##_t class_##
* convenience macro for conditional guards that calls the statement that
* follows only if the lock was not acquired (typically an error return).
*
+ * Only for conditional locks.
+ *
* 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
@@ -290,7 +292,6 @@ static inline class_##_name##_t class_##
* acquire fails.
*
* Only for conditional locks.
- *
*/
#define __DEFINE_CLASS_IS_CONDITIONAL(_name, _is_cond) \
@@ -342,6 +343,7 @@ _label: \
__UNIQUE_ID(label), args)
#define __if_not_guard(_name, _id, args...) \
+ BUILD_BUG_ON(!__is_cond_ptr(_name)); \
CLASS(_name, _id)(args); \
if (!__guard_ptr(_name)(&_id))
That make sense to people?
despite name, looks promising!
I've queued these two patches:
git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git locking/core
But lacking if_not_guard() users, the robot isn't really going to give
me much feedback there, I suppose...
Couldn't you just pick the other patches, that use the newly introduced
macro?
