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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
This commit is contained in:
Brian Behlendorf 2015-06-03 10:42:36 -07:00
parent a876b0305e
commit 86c16c59fe
3 changed files with 2 additions and 50 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
config/spl-build.m4
View File

@ -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.

24
include/linux/rwsem_compat.h
View File

@ -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 */

6
include/sys/rwlock.h
View File

@ -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