| Message ID | 20240205142613.23914-2-fabio.maria.de.francesco@linux.intel.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Add cond_guard() to conditional guards | expand |
On Mon, 5 Feb 2024 15:26:12 +0100 "Fabio M. De Francesco" <fabio.maria.de.francesco@linux.intel.com> 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 more statements in a block) that is passed to its > second argument. That statement (or block) is executed if waiting for a > lock is interrupted or if a _trylock() fails in case of contention. > > Usage example: > > cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); > > Consistently with the other guards, locks are unlocked at the exit of the > scope where cond_guard() is called. > > 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> This version looks good to me, but these are still fairly new to me so good to get inputs from others. Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> > --- > include/linux/cleanup.h | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h > index c2d09bc4f976..88af56600325 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' are one or more > + * statements that are executed when waiting for a lock is interrupted or > + * when a _trylock() fails in case of contention. > + * > + * Example: > + * > + * cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); > + * > * 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 +175,10 @@ 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 > + > #define scoped_guard(_name, args...) \ > for (CLASS(_name, scope)(args), \ > *done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)
On 2/5/24 7:26 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 more statements in a block) that is passed to its > second argument. That statement (or block) is executed if waiting for a > lock is interrupted or if a _trylock() fails in case of contention. > > Usage example: > > cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); > > Consistently with the other guards, locks are unlocked at the exit of the > scope where cond_guard() is called. > > 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 | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h > index c2d09bc4f976..88af56600325 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' are one or more > + * statements that are executed when waiting for a lock is interrupted or > + * when a _trylock() fails in case of contention. > + * > + * Example: > + * > + * cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); > + * > * 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 +175,10 @@ 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 > + > #define scoped_guard(_name, args...) \ > for (CLASS(_name, scope)(args), \ > *done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)
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 more statements in a block) that is passed to its > second argument. That statement (or block) is executed if waiting for a > lock is interrupted or if a _trylock() fails in case of contention. > > Usage example: > > cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); > > Consistently with the other guards, locks are unlocked at the exit of the > scope where cond_guard() is called. > > 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 | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h > index c2d09bc4f976..88af56600325 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' are one or more > + * statements that are executed when waiting for a lock is interrupted or > + * when a _trylock() fails in case of contention. > + * > + * Example: > + * > + * cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); That _fail argument likely needs to be a statement expression for the multi-statement case. > + * > * 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 +175,10 @@ 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 No, as I stated before this is broken for usages of: if () cond_guard() else if () The 'else' in the definition is critical, this builds for me (untested): diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h index 88af56600325..665407498781 100644 --- a/include/linux/cleanup.h +++ b/include/linux/cleanup.h @@ -142,7 +142,7 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \ * * Example: * - * cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); + * cond_guard(rwsem_read_try, ({ printk(...); return 0; }), &semaphore); * * scoped_guard (name, args...) { }: * similar to CLASS(name, scope)(args), except the variable (with the @@ -177,7 +177,8 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \ #define cond_guard(_name, _fail, args...) \ CLASS(_name, scope)(args); \ - if (!__guard_ptr(_name)(&scope)) _fail + if (!__guard_ptr(_name)(&scope)) _fail; \ + else #define scoped_guard(_name, args...) \ for (CLASS(_name, scope)(args), \
Dan Williams wrote: > 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 more statements in a block) that is passed to its > > second argument. That statement (or block) is executed if waiting for a > > lock is interrupted or if a _trylock() fails in case of contention. > > > > Usage example: > > > > cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); > > > > Consistently with the other guards, locks are unlocked at the exit of the > > scope where cond_guard() is called. > > > > 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 | 14 ++++++++++++++ > > 1 file changed, 14 insertions(+) > > > > diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h > > index c2d09bc4f976..88af56600325 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' are one or more > > + * statements that are executed when waiting for a lock is interrupted or > > + * when a _trylock() fails in case of contention. > > + * > > + * Example: > > + * > > + * cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); > > That _fail argument likely needs to be a statement expression for the > multi-statement case. You mean ({ ... }) as discussed here? https://lore.kernel.org/all/65c1578c76def_37447929456@iweiny-mobl.notmuch/ > > > + * > > * 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 +175,10 @@ 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 > > No, as I stated before this is broken for usages of: > > if () cond_guard() else if () > > The 'else' in the definition is critical, this builds for me (untested): I did not test Fabios work directly but I don't understand this example. It seems like your suggestion does nothing useful. The cond_guard() becomes a single statement like... if () cond_guard(); else ... ... And can't protect anything. NOTE From my understanding of cond_guard() as defined, the ';' must be used as part of cond_guard() and should complete the internal macro 'if' statement. I think this would work: if () { cond_guard(); ... do locked stuff ... } else ... > > diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h > index 88af56600325..665407498781 100644 > --- a/include/linux/cleanup.h > +++ b/include/linux/cleanup.h > @@ -142,7 +142,7 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \ > * > * Example: > * > - * cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); > + * cond_guard(rwsem_read_try, ({ printk(...); return 0; }), &semaphore); > * > * scoped_guard (name, args...) { }: > * similar to CLASS(name, scope)(args), except the variable (with the > @@ -177,7 +177,8 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \ > > #define cond_guard(_name, _fail, args...) \ > CLASS(_name, scope)(args); \ > - if (!__guard_ptr(_name)(&scope)) _fail > + if (!__guard_ptr(_name)(&scope)) _fail; \ Building on what I found for scoped_cond_guard() this should be > + if (!__guard_ptr(_name)(&scope)) { _fail; } And drop the else. The else needs to clearly be part of an outside if in your example. Ira > + else > > #define scoped_guard(_name, args...) \ > for (CLASS(_name, scope)(args), \
Ira Weiny wrote: > Dan Williams wrote: > > 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 more statements in a block) that is passed to its > > > second argument. That statement (or block) is executed if waiting for a > > > lock is interrupted or if a _trylock() fails in case of contention. > > > > > > Usage example: > > > > > > cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); > > > > > > Consistently with the other guards, locks are unlocked at the exit of the > > > scope where cond_guard() is called. > > > > > > 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 | 14 ++++++++++++++ > > > 1 file changed, 14 insertions(+) > > > > > > diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h > > > index c2d09bc4f976..88af56600325 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' are one or more > > > + * statements that are executed when waiting for a lock is interrupted or > > > + * when a _trylock() fails in case of contention. > > > + * > > > + * Example: > > > + * > > > + * cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); > > > > That _fail argument likely needs to be a statement expression for the > > multi-statement case. > > You mean ({ ... }) as discussed here? > > https://lore.kernel.org/all/65c1578c76def_37447929456@iweiny-mobl.notmuch/ Yes. > > > + * > > > * 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 +175,10 @@ 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 > > > > No, as I stated before this is broken for usages of: > > > > if () cond_guard() else if () > > > > The 'else' in the definition is critical, this builds for me (untested): > > I did not test Fabios work directly but I don't understand this example. > It seems like your suggestion does nothing useful. The cond_guard() > becomes a single statement like... > > if () > cond_guard(); > else ... > > ... And can't protect anything. A sequence to acquire and drop a lock is sometimes a barrier semantic. Is it typical, no, is it possible, yes. I otherwise do not understand the need to include the subtle side effect. > cond_guard() as defined, the ';' must be used as part of cond_guard() and > should complete the internal macro 'if' statement. > > I think this would work: > > if () { > cond_guard(); > ... do locked stuff ... > } else ... > > > > > diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h > > index 88af56600325..665407498781 100644 > > --- a/include/linux/cleanup.h > > +++ b/include/linux/cleanup.h > > @@ -142,7 +142,7 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \ > > * > > * Example: > > * > > - * cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); > > + * cond_guard(rwsem_read_try, ({ printk(...); return 0; }), &semaphore); > > * > > * scoped_guard (name, args...) { }: > > * similar to CLASS(name, scope)(args), except the variable (with the > > @@ -177,7 +177,8 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \ > > > > #define cond_guard(_name, _fail, args...) \ > > CLASS(_name, scope)(args); \ > > - if (!__guard_ptr(_name)(&scope)) _fail > > + if (!__guard_ptr(_name)(&scope)) _fail; \ > > Building on what I found for scoped_cond_guard() this should be > > > + if (!__guard_ptr(_name)(&scope)) { _fail; } That's still a dangling if () statement. > > And drop the else. The else needs to clearly be part of an outside if in > your example. Please just rely on a statement-expression for the odd multi-statement _fail use case and include the else in the definition to remove any room for confusion.
Dan Williams wrote: > Ira Weiny wrote: > > Dan Williams wrote: > > > 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 more statements in a block) that is passed to its > > > > second argument. That statement (or block) is executed if waiting for a > > > > lock is interrupted or if a _trylock() fails in case of contention. > > > > > > > > Usage example: > > > > > > > > cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); > > > > > > > > Consistently with the other guards, locks are unlocked at the exit of the > > > > scope where cond_guard() is called. > > > > > > > > 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 | 14 ++++++++++++++ > > > > 1 file changed, 14 insertions(+) > > > > > > > > diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h > > > > index c2d09bc4f976..88af56600325 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' are one or more > > > > + * statements that are executed when waiting for a lock is interrupted or > > > > + * when a _trylock() fails in case of contention. > > > > + * > > > > + * Example: > > > > + * > > > > + * cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); > > > > > > That _fail argument likely needs to be a statement expression for the > > > multi-statement case. > > > > You mean ({ ... }) as discussed here? > > > > https://lore.kernel.org/all/65c1578c76def_37447929456@iweiny-mobl.notmuch/ > > Yes. > > > > > + * > > > > * 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 +175,10 @@ 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 > > > > > > No, as I stated before this is broken for usages of: > > > > > > if () cond_guard() else if () > > > > > > The 'else' in the definition is critical, this builds for me (untested): > > > > I did not test Fabios work directly but I don't understand this example. > > It seems like your suggestion does nothing useful. The cond_guard() > > becomes a single statement like... > > > > if () > > cond_guard(); > > else ... > > > > ... And can't protect anything. > > A sequence to acquire and drop a lock is sometimes a barrier semantic. > Is it typical, no, is it possible, yes. I otherwise do not understand > the need to include the subtle side effect. I was not trying to include a subtle side effect. I was thinking that the else block would be the only block covered by the lock. I've looked at the preprocessor output again and I now see what you are saying. Also I see I was thinking incorrectly. The else will be an empty statement and the rest of the outer block will be covered by the lock... Sorry for not seeing this before. > > cond_guard() as defined, the ';' must be used as part of cond_guard() and > > should complete the internal macro 'if' statement. > > > > I think this would work: > > > > if () { > > cond_guard(); > > ... do locked stuff ... > > } else ... > > > > > > > > diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h > > > index 88af56600325..665407498781 100644 > > > --- a/include/linux/cleanup.h > > > +++ b/include/linux/cleanup.h > > > @@ -142,7 +142,7 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \ > > > * > > > * Example: > > > * > > > - * cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); > > > + * cond_guard(rwsem_read_try, ({ printk(...); return 0; }), &semaphore); > > > * > > > * scoped_guard (name, args...) { }: > > > * similar to CLASS(name, scope)(args), except the variable (with the > > > @@ -177,7 +177,8 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \ > > > > > > #define cond_guard(_name, _fail, args...) \ > > > CLASS(_name, scope)(args); \ > > > - if (!__guard_ptr(_name)(&scope)) _fail > > > + if (!__guard_ptr(_name)(&scope)) _fail; \ > > > > Building on what I found for scoped_cond_guard() this should be > > > > > + if (!__guard_ptr(_name)(&scope)) { _fail; } > > That's still a dangling if () statement. > > > > > And drop the else. The else needs to clearly be part of an outside if in > > your example. > > Please just rely on a statement-expression for the odd multi-statement _fail > use case and include the else in the definition to remove any room for > confusion. Yea ok I see it now, Ira
diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h index c2d09bc4f976..88af56600325 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' are one or more + * statements that are executed when waiting for a lock is interrupted or + * when a _trylock() fails in case of contention. + * + * Example: + * + * cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); + * * 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 +175,10 @@ 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 + #define scoped_guard(_name, args...) \ for (CLASS(_name, scope)(args), \ *done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)
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 more statements in a block) that is passed to its second argument. That statement (or block) is executed if waiting for a lock is interrupted or if a _trylock() fails in case of contention. Usage example: cond_guard(rwsem_read_try, { printk(...); return 0; }, &semaphore); Consistently with the other guards, locks are unlocked at the exit of the scope where cond_guard() is called. 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 | 14 ++++++++++++++ 1 file changed, 14 insertions(+)