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authorChunwei Chen <david.chen@osnexus.com>2016-04-12 12:05:14 -0700
committerBrian Behlendorf <behlendorf1@llnl.gov>2016-04-25 17:04:07 -0700
commitcdd39dd2457ac57622339669db0536a580374bd3 (patch)
tree71a77ae2758f91df5385fe4e6181eb755e619422
parent224817e2a81912b46453a96b9eec4804856c801b (diff)
Use kernel provided mutex owner
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
-rw-r--r--config/spl-build.m429
-rw-r--r--include/sys/mutex.h15
2 files changed, 44 insertions, 0 deletions
diff --git a/config/spl-build.m4 b/config/spl-build.m4
index b9c04a95e..55453c822 100644
--- a/config/spl-build.m4
+++ b/config/spl-build.m4
@@ -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"
+])
diff --git a/include/sys/mutex.h b/include/sys/mutex.h
index fba35f3f9..319235223 100644
--- a/include/sys/mutex.h
+++ b/include/sys/mutex.h
@@ -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))