diff mbox series

[03/20] mmiowb: Hook up mmiowb helpers to spinlocks and generic I/O accessors

Message ID 20190301140348.25175-4-will.deacon@arm.com
State New
Headers show
Series Remove Mysterious Macro Intended to Obscure Weird Behaviours (mmiowb()) | expand

Commit Message

Will Deacon March 1, 2019, 2:03 p.m. UTC 
Removing explicit calls to mmiowb() from driver code means that we must
now call into the generic mmiowb_spin_{lock,unlock}() functions from the
core spinlock code. In order to elide barriers following critical
sections without any I/O writes, we also hook into the asm-generic I/O
routines.

Signed-off-by: Will Deacon <will.deacon@arm.com>

---
 include/asm-generic/io.h        |  3 ++-
 include/linux/spinlock.h        | 11 ++++++++++-
 kernel/locking/spinlock_debug.c |  6 +++++-
 3 files changed, 17 insertions(+), 3 deletions(-)

-- 
2.11.0

Comments

Nicholas Piggin March 3, 2019, 1:47 a.m. UTC | #1 
Will Deacon's on March 2, 2019 12:03 am:
> @@ -177,6 +178,7 @@ do {								\

>  static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)

>  {

>  	__acquire(lock);

> +	mmiowb_spin_lock();

>  	arch_spin_lock(&lock->raw_lock);

>  }

>  

> @@ -188,16 +190,23 @@ static inline void

>  do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)

>  {

>  	__acquire(lock);

> +	mmiowb_spin_lock();

>  	arch_spin_lock_flags(&lock->raw_lock, *flags);

>  }


You'd be better to put these inside the spin lock, to match your 
trylock.

Also it means the mmiowb state can be used inside a lock/unlock pair
without a compiler barrer forcing it to be reloaded, should be better
code generation for very small critical sections on archs which inline
lock and unlock.

>  

>  static inline int do_raw_spin_trylock(raw_spinlock_t *lock)

>  {

> -	return arch_spin_trylock(&(lock)->raw_lock);

> +	int ret = arch_spin_trylock(&(lock)->raw_lock);

> +

> +	if (ret)

> +		mmiowb_spin_lock();

> +

> +	return ret;

>  }

>  

>  static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)

>  {

> +	mmiowb_spin_unlock();

>  	arch_spin_unlock(&lock->raw_lock);

>  	__release(lock);

>  }


Thanks,
Nick
diff mbox series

Patch

diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index 303871651f8a..bc490a746602 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -19,6 +19,7 @@ 
 #include <asm-generic/iomap.h>
 #endif
 
+#include <asm/mmiowb.h>
 #include <asm-generic/pci_iomap.h>
 
 #ifndef mmiowb
@@ -49,7 +50,7 @@ 
 
 /* serialize device access against a spin_unlock, usually handled there. */
 #ifndef __io_aw
-#define __io_aw()      barrier()
+#define __io_aw()      mmiowb_set_pending()
 #endif
 
 #ifndef __io_pbw
diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index e089157dcf97..4298b1b31d9b 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -57,6 +57,7 @@ 
 #include <linux/stringify.h>
 #include <linux/bottom_half.h>
 #include <asm/barrier.h>
+#include <asm/mmiowb.h>
 
 
 /*
@@ -177,6 +178,7 @@  do {								\
 static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
 {
 	__acquire(lock);
+	mmiowb_spin_lock();
 	arch_spin_lock(&lock->raw_lock);
 }
 
@@ -188,16 +190,23 @@  static inline void
 do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)
 {
 	__acquire(lock);
+	mmiowb_spin_lock();
 	arch_spin_lock_flags(&lock->raw_lock, *flags);
 }
 
 static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
 {
-	return arch_spin_trylock(&(lock)->raw_lock);
+	int ret = arch_spin_trylock(&(lock)->raw_lock);
+
+	if (ret)
+		mmiowb_spin_lock();
+
+	return ret;
 }
 
 static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
 {
+	mmiowb_spin_unlock();
 	arch_spin_unlock(&lock->raw_lock);
 	__release(lock);
 }
diff --git a/kernel/locking/spinlock_debug.c b/kernel/locking/spinlock_debug.c
index 9aa0fccd5d43..654484b6e70c 100644
--- a/kernel/locking/spinlock_debug.c
+++ b/kernel/locking/spinlock_debug.c
@@ -109,6 +109,7 @@  static inline void debug_spin_unlock(raw_spinlock_t *lock)
  */
 void do_raw_spin_lock(raw_spinlock_t *lock)
 {
+	mmiowb_spin_lock();
 	debug_spin_lock_before(lock);
 	arch_spin_lock(&lock->raw_lock);
 	debug_spin_lock_after(lock);
@@ -118,8 +119,10 @@  int do_raw_spin_trylock(raw_spinlock_t *lock)
 {
 	int ret = arch_spin_trylock(&lock->raw_lock);
 
-	if (ret)
+	if (ret) {
+		mmiowb_spin_lock();
 		debug_spin_lock_after(lock);
+	}
 #ifndef CONFIG_SMP
 	/*
 	 * Must not happen on UP:
@@ -131,6 +134,7 @@  int do_raw_spin_trylock(raw_spinlock_t *lock)
 
 void do_raw_spin_unlock(raw_spinlock_t *lock)
 {
+	mmiowb_spin_unlock();
 	debug_spin_unlock(lock);
 	arch_spin_unlock(&lock->raw_lock);
 }