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s390/spinlock: Implement SPINLOCK_LOCKVAL with inline assembly

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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: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2025-03-10 10:33:41 +01:00 committed by Vasily Gorbik
parent 4797e9b506
commit b46525437e
2 changed files with 21 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
arch/s390/include/asm/spinlock.h
View File

@ -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)

6
arch/s390/lib/spinlock.c
View File

@ -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--) {