Retire rwsem_is_locked() compat

Stock Linux 2.6.32 and earlier kernels contained a broken version of
rwsem_is_locked() which could return an incorrect value.  Because of
this compatibility code was added to detect the broken implementation
and replace it with our own if needed.

The fix for this issue was merged in to the mainline Linux kernel as
of 2.6.33 and the major enterprise distributions based on 2.6.32 have
all backported the fix.  Therefore there is no longer a need to carry
this code and it can be removed.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #454

diff --git a/config/spl-build.m4 b/config/spl-build.m4
index 3bfc1e2325e25242d28d0ac43c6b96db8b2da513..9999d480d0c4363b635182f6239788b2ee6c4da3 100644 (file)
--- a/config/spl-build.m4
+++ b/config/spl-build.m4
@@ -33,7 +33,6 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [
        SPL_AC_FS_STRUCT_SPINLOCK
        SPL_AC_KUIDGID_T
        SPL_AC_PUT_TASK_STRUCT
-       SPL_AC_EXPORTED_RWSEM_IS_LOCKED
        SPL_AC_KERNEL_FALLOCATE
        SPL_AC_CONFIG_ZLIB_INFLATE
        SPL_AC_CONFIG_ZLIB_DEFLATE
@@ -1201,27 +1200,6 @@ AC_DEFUN([SPL_AC_KERNEL_FALLOCATE], [
        SPL_AC_PAX_KERNEL_FILE_FALLOCATE
 ])
 
-dnl #
-dnl # 2.6.33 API change. Also backported in RHEL5 as of 2.6.18-190.el5.
-dnl # Earlier versions of rwsem_is_locked() were inline and had a race
-dnl # condition.  The fixed version is exported as a symbol.  The race
-dnl # condition is fixed by acquiring sem->wait_lock, so we must not
-dnl # call that version while holding sem->wait_lock.
-dnl #
-AC_DEFUN([SPL_AC_EXPORTED_RWSEM_IS_LOCKED],
-       [AC_MSG_CHECKING([whether rwsem_is_locked() acquires sem->wait_lock])
-       SPL_LINUX_TRY_COMPILE_SYMBOL([
-               #include <linux/rwsem.h>
-               int rwsem_is_locked(struct rw_semaphore *sem) { return 0; }
-       ], [], [rwsem_is_locked], [lib/rwsem-spinlock.c], [
-               AC_MSG_RESULT(yes)
-               AC_DEFINE(RWSEM_IS_LOCKED_TAKES_WAIT_LOCK, 1,
-                         [rwsem_is_locked() acquires sem->wait_lock])
-       ], [
-               AC_MSG_RESULT(no)
-       ])
-])
-
 dnl #
 dnl # zlib inflate compat,
 dnl # Verify the kernel has CONFIG_ZLIB_INFLATE support enabled.

diff --git a/include/linux/rwsem_compat.h b/include/linux/rwsem_compat.h
index 80f348e4c25abbe6556970090fc38975376275b8..5841d7c286978011df049ecbc2520edb249bdf7a 100644 (file)
--- a/include/linux/rwsem_compat.h
+++ b/include/linux/rwsem_compat.h
@@ -37,30 +37,6 @@
 #define spl_rwsem_trylock_irqsave(lk, fl)    spin_trylock_irqsave(lk, fl)
 #endif /* RWSEM_SPINLOCK_IS_RAW */
 
-/*
- * Prior to Linux 2.6.33 there existed a race condition in rwsem_is_locked().
- * The semaphore's activity was checked outside of the wait_lock which
- * could result in some readers getting the incorrect activity value.
- *
- * When a kernel without this fix is detected the SPL takes responsibility
- * for acquiring the wait_lock to avoid this race.
- */
-#if defined(RWSEM_IS_LOCKED_TAKES_WAIT_LOCK)
 #define spl_rwsem_is_locked(rwsem)           rwsem_is_locked(rwsem)
-#else
-static inline int
-spl_rwsem_is_locked(struct rw_semaphore *rwsem)
-{
-       unsigned long flags;
-       int rc = 1;
-
-       if (spl_rwsem_trylock_irqsave(&rwsem->wait_lock, flags)) {
-               rc = rwsem_is_locked(rwsem);
-               spl_rwsem_unlock_irqrestore(&rwsem->wait_lock, flags);
-       }
-
-       return (rc);
-}
-#endif /* RWSEM_IS_LOCKED_TAKES_WAIT_LOCK */
 
 #endif /* _SPL_RWSEM_COMPAT_H */

diff --git a/include/sys/rwlock.h b/include/sys/rwlock.h
index 9dfbfe5451a50d07db46200bd8b05478f79e2afb..7064e8f1f2018a162ceae6097bf7b80a49948fdd 100644 (file)
--- a/include/sys/rwlock.h
+++ b/include/sys/rwlock.h
@@ -83,15 +83,13 @@ rw_owner(krwlock_t *rwp)
 static inline int
 RW_READ_HELD(krwlock_t *rwp)
 {
-       return (spl_rwsem_is_locked(SEM(rwp)) &&
-               rw_owner(rwp) == NULL);
+       return (spl_rwsem_is_locked(SEM(rwp)) && rw_owner(rwp) == NULL);
 }
 
 static inline int
 RW_WRITE_HELD(krwlock_t *rwp)
 {
-       return (spl_rwsem_is_locked(SEM(rwp)) &&
-               rw_owner(rwp) == current);
+       return (spl_rwsem_is_locked(SEM(rwp)) && rw_owner(rwp) == current);
 }
 
 static inline int