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| author |   Jonathan Corbet <corbet@lwn.net> | 2008-05-18 14:27:41 -0600 |
|---|---|---|
| committer | Jonathan Corbet <corbet@lwn.net> | 2008-06-20 14:05:53 -0600 |
| commit | 0b2806768899dba5967bcd4a3b93eaed9a1dc4f3 (patch) | |
| tree | c9e7762d9b236883f4a23a170919317a6e7c93c7 | |
| parent | videodev: BKL pushdown (diff) | |
| download | linux-dev-0b2806768899dba5967bcd4a3b93eaed9a1dc4f3.tar.xz linux-dev-0b2806768899dba5967bcd4a3b93eaed9a1dc4f3.zip | |
Add cycle_kernel_lock()
A number of driver functions are so obviously trivial that they do not need
the big kernel lock - at least not overtly. It turns out that the
acquisition of the BKL in driver open() functions can perform a sort of
poor-hacker's serialization function, delaying the open operation until the
driver is certain to have completed its initialization. Add a simple
cycle_kernel_lock() function for these cases to make it clear that there is
no need to *hold* the BKL, just to be sure that we can acquire it.
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
| -rw-r--r-- | include/linux/smp_lock.h | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/include/linux/smp_lock.h b/include/linux/smp_lock.h index aab3a4cff4e1..813be59bf345 100644 --- a/include/linux/smp_lock.h +++ b/include/linux/smp_lock.h @@ -27,11 +27,24 @@ static inline int reacquire_kernel_lock(struct task_struct *task) extern void __lockfunc lock_kernel(void) __acquires(kernel_lock); extern void __lockfunc unlock_kernel(void) __releases(kernel_lock); +/* + * Various legacy drivers don't really need the BKL in a specific + * function, but they *do* need to know that the BKL became available. + * This function just avoids wrapping a bunch of lock/unlock pairs + * around code which doesn't really need it. + */ +static inline void cycle_kernel_lock(void) +{ + lock_kernel(); + unlock_kernel(); +} + #else #define lock_kernel() do { } while(0) #define unlock_kernel() do { } while(0) #define release_kernel_lock(task) do { } while(0) +#define cycle_kernel_lock() do { } while(0) #define reacquire_kernel_lock(task) 0 #define kernel_locked() 1 |