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Use kernel provided mutex owner

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To reduce mutex footprint, we detect the existence of owner in kernel mutex,
and rely on it if it exists.

Note that before Linux 3.0, mutex owner is of type thread_info. Also note
that, in Linux 3.18, the condition for owner is changed from
CONFIG_DEBUG_MUTEXES || CONFIG_SMP to
CONFIG_DEBUG_MUTEXES || CONFIG_MUTEX_SPIN_ON_OWNER

Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #540
This commit is contained in:
Chunwei Chen 2016-04-12 12:05:14 -07:00 committed by Brian Behlendorf
parent 224817e2a8
commit cdd39dd245
2 changed files with 44 additions and 0 deletions
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29
config/spl-build.m4
View File

@ -44,6 +44,7 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [
SPL_AC_USLEEP_RANGE
SPL_AC_KMEM_CACHE_ALLOCFLAGS
SPL_AC_WAIT_ON_BIT
SPL_AC_MUTEX_OWNER
])
AC_DEFUN([SPL_AC_MODULE_SYMVERS], [
@ -1447,3 +1448,31 @@ AC_DEFUN([SPL_AC_WAIT_ON_BIT], [
AC_MSG_RESULT(no)
])
])
dnl #
dnl # Check whether mutex has owner with task_struct type.
dnl #
dnl # Note that before Linux 3.0, mutex owner is of type thread_info.
dnl #
dnl # Note that in Linux 3.18, the condition for owner is changed from
dnl # defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_SMP) to
dnl # defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_MUTEX_SPIN_ON_OWNER)
dnl #
AC_DEFUN([SPL_AC_MUTEX_OWNER], [
AC_MSG_CHECKING([whether mutex has owner])
tmp_flags="$EXTRA_KCFLAGS"
EXTRA_KCFLAGS="-Werror"
SPL_LINUX_TRY_COMPILE([
#include <linux/mutex.h>
],[
DEFINE_MUTEX(m);
struct task_struct *t __attribute__ ((unused));
t = m.owner;
],[
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_MUTEX_OWNER, 1, [yes])
],[
AC_MSG_RESULT(no)
])
EXTRA_KCFLAGS="$tmp_flags"
])

15
include/sys/mutex.h
View File

@ -40,7 +40,10 @@ typedef enum {
typedef struct {
struct mutex m_mutex;
spinlock_t m_lock; /* used for serializing mutex_exit */
#ifndef HAVE_MUTEX_OWNER
/* only when kernel doesn't have owner */
kthread_t *m_owner;
#endif
#ifdef CONFIG_LOCKDEP
kmutex_type_t m_type;
#endif /* CONFIG_LOCKDEP */
@ -51,16 +54,28 @@ typedef struct {
static inline void
spl_mutex_set_owner(kmutex_t *mp)
{
/*
* kernel will handle its owner, so we don't need to do anything if it
* is defined.
*/
#ifndef HAVE_MUTEX_OWNER
mp->m_owner = current;
#endif
}
static inline void
spl_mutex_clear_owner(kmutex_t *mp)
{
#ifndef HAVE_MUTEX_OWNER
mp->m_owner = NULL;
#endif
}
#ifdef HAVE_MUTEX_OWNER
#define mutex_owner(mp) (ACCESS_ONCE(MUTEX(mp)->owner))
#else
#define mutex_owner(mp) (ACCESS_ONCE((mp)->m_owner))
#endif
#define mutex_owned(mp) (mutex_owner(mp) == current)
#define MUTEX_HELD(mp) mutex_owned(mp)
#define MUTEX_NOT_HELD(mp) (!MUTEX_HELD(mp))