Commit b4652543 authored by Heiko Carstens's avatar Heiko Carstens Committed by Vasily Gorbik
Browse files

s390/spinlock: Implement SPINLOCK_LOCKVAL with inline assembly 



Implement SPINLOCK_LOCKVAL with an inline assembly, which makes use of the
ALTERNATIVE macro, to read spinlock_lockval from lowcore. Provide an
alternative instruction with a different offset in case lowcore is
relocated.

This replaces sequences of two instructions with one instruction.

Before:
  10602a:       a7 78 00 00             lhi     %r7,0
  10602e:       a5 8e 00 00             llilh   %r8,0
  106032:       58 d0 83 ac             l       %r13,940(%r8)
  106036:       ba 7d b5 80             cs      %r7,%r13,1408(%r11)

After:
  10602a:       a7 88 00 00             lhi     %r8,0
  10602e:       e3 70 03 ac 00 58       ly      %r7,940
  106034:       ba 87 b5 80             cs      %r8,%r7,1408(%r11)

Kernel image size change:
add/remove: 756/750 grow/shrink: 646/3435 up/down: 30778/-46326 (-15548)

Acked-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 4797e9b5

arch/s390/include/asm/spinlock.h

+18 −2
Original line number Diff line number Diff line
@@ -16,7 +16,23 @@ 
#include <asm/processor.h>

#include <asm/alternative.h>



#define SPINLOCK_LOCKVAL (get_lowcore()->spinlock_lockval)

static __always_inline unsigned int spinlock_lockval(void)

{

	unsigned long lc_lockval;

	unsigned int lockval;



	BUILD_BUG_ON(sizeof_field(struct lowcore, spinlock_lockval) != sizeof(lockval));

	lc_lockval = offsetof(struct lowcore, spinlock_lockval);

	asm_inline(

		ALTERNATIVE("   ly      %[lockval],%[offzero](%%r0)\n",

			    "   ly      %[lockval],%[offalt](%%r0)\n",

			    ALT_FEATURE(MFEATURE_LOWCORE))

		: [lockval] "=d" (lockval)

		: [offzero] "i" (lc_lockval),

		  [offalt] "i" (lc_lockval + LOWCORE_ALT_ADDRESS),

		  "m" (((struct lowcore *)0)->spinlock_lockval));

	return lockval;

}



extern int spin_retry;
@@ -60,7 +76,7 @@ static inline int arch_spin_trylock_once(arch_spinlock_t *lp) 
	int old = 0;



	barrier();

	return likely(arch_try_cmpxchg(&lp->lock, &old, SPINLOCK_LOCKVAL));

	return likely(arch_try_cmpxchg(&lp->lock, &old, spinlock_lockval()));

}



static inline void arch_spin_lock(arch_spinlock_t *lp)

arch/s390/lib/spinlock.c

+3 −3
Original line number Diff line number Diff line
@@ -160,7 +160,7 @@ static inline void arch_spin_lock_queued(arch_spinlock_t *lp) 


	ix = get_lowcore()->spinlock_index++;

	barrier();

	lockval = SPINLOCK_LOCKVAL;	/* cpu + 1 */

	lockval = spinlock_lockval();	/* cpu + 1 */

	node = this_cpu_ptr(&spin_wait[ix]);

	node->prev = node->next = NULL;

	node_id = node->node_id;
@@ -251,7 +251,7 @@ static inline void arch_spin_lock_classic(arch_spinlock_t *lp) 
{

	int lockval, old, new, owner, count;



	lockval = SPINLOCK_LOCKVAL;	/* cpu + 1 */

	lockval = spinlock_lockval();	/* cpu + 1 */



	/* Pass the virtual CPU to the lock holder if it is not running */

	owner = arch_spin_yield_target(READ_ONCE(lp->lock), NULL);
@@ -290,7 +290,7 @@ EXPORT_SYMBOL(arch_spin_lock_wait); 


int arch_spin_trylock_retry(arch_spinlock_t *lp)

{

	int cpu = SPINLOCK_LOCKVAL;

	int cpu = spinlock_lockval();

	int owner, count;



	for (count = spin_retry; count > 0; count--) {