[PATCH] locking: remove spin_lock_flags() etc

Arnd Bergmann
2021-10-22T12:01:13Z

From: Arnd Bergmann <arnd@arndb.de>

parisc, ia64 and powerpc32 are the only remaining architectures that
provide custom arch_{spin,read,write}_lock_flags() functions, which are
meant to re-enable interrupts while waiting for a spinlock.

However, none of these can actually run into this codepath, because
it is only called on architectures without CONFIG_GENERIC_LOCKBREAK,
or when CONFIG_DEBUG_LOCK_ALLOC is set without CONFIG_LOCKDEP, and none
of those combinations are possible on the three architectures.

Going back in the git history, it appears that arch/mn10300 may have
been able to run into this code path, but there is a good chance that
it never worked. On the architectures that still exist, it was
already impossible to hit back in 2008 after the introduction of
CONFIG_GENERIC_LOCKBREAK, and possibly earlier.

As this is all dead code, just remove it and the helper functions built
around it. For arch/ia64, the inline asm could be cleaned up, but
it seems safer to leave it untouched.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
arch/ia64/include/asm/spinlock.h | 23 ++++++----------------
arch/openrisc/include/asm/spinlock.h | 3 ---
arch/parisc/include/asm/spinlock.h | 15 --------------
arch/powerpc/include/asm/simple_spinlock.h | 21 --------------------
arch/s390/include/asm/spinlock.h | 8 --------
include/linux/lockdep.h | 17 ----------------
include/linux/rwlock.h | 15 --------------
include/linux/rwlock_api_smp.h | 6 ++----
include/linux/spinlock.h | 13 ------------
include/linux/spinlock_api_smp.h | 9 ---------
include/linux/spinlock_up.h | 1 -
kernel/locking/spinlock.c | 3 +--
12 files changed, 9 insertions(+), 125 deletions(-)

diff --git a/arch/ia64/include/asm/spinlock.h b/arch/ia64/include/asm/spinlock.h
index 864775970c50..0e5c1ad3239c 100644
--- a/arch/ia64/include/asm/spinlock.h
+++ b/arch/ia64/include/asm/spinlock.h
@@ -124,18 +124,13 @@ static __always_inline void arch_spin_unlock(arch_spinlock_t *lock)
__ticket_spin_unlock(lock);
}

-static __always_inline void arch_spin_lock_flags(arch_spinlock_t *lock,
- unsigned long flags)
-{
- arch_spin_lock(lock);
-}
-#define arch_spin_lock_flags arch_spin_lock_flags
-
#ifdef ASM_SUPPORTED

static __always_inline void
-arch_read_lock_flags(arch_rwlock_t *lock, unsigned long flags)
+arch_read_lock(arch_rwlock_t *lock)
{
+ unsigned long flags = 0;
+
__asm__ __volatile__ (
"tbit.nz p6, p0 = %1,%2\n"
"br.few 3f\n"
@@ -157,13 +152,8 @@ arch_read_lock_flags(arch_rwlock_t *lock, unsigned long flags)
: "p6", "p7", "r2", "memory");
}

-#define arch_read_lock_flags arch_read_lock_flags
-#define arch_read_lock(lock) arch_read_lock_flags(lock, 0)
-
#else /* !ASM_SUPPORTED */

-#define arch_read_lock_flags(rw, flags) arch_read_lock(rw)
-
#define arch_read_lock(rw) \
do { \
arch_rwlock_t *__read_lock_ptr = (rw); \
@@ -186,8 +176,10 @@ do { \
#ifdef ASM_SUPPORTED

static __always_inline void
-arch_write_lock_flags(arch_rwlock_t *lock, unsigned long flags)
+arch_write_lock(arch_rwlock_t *lock)
{
+ unsigned long flags = 0;
+
__asm__ __volatile__ (
"tbit.nz p6, p0 = %1, %2\n"
"mov ar.ccv = r0\n"
@@ -210,9 +202,6 @@ arch_write_lock_flags(arch_rwlock_t *lock, unsigned long flags)
: "ar.ccv", "p6", "p7", "r2", "r29", "memory");
}

-#define arch_write_lock_flags arch_write_lock_flags
-#define arch_write_lock(rw) arch_write_lock_flags(rw, 0)
-
#define arch_write_trylock(rw) \
({ \
register long result; \
diff --git a/arch/openrisc/include/asm/spinlock.h b/arch/openrisc/include/asm/spinlock.h
index a8940bdfcb7e..264944a71535 100644
--- a/arch/openrisc/include/asm/spinlock.h
+++ b/arch/openrisc/include/asm/spinlock.h
@@ -19,9 +19,6 @@

#include <asm/qrwlock.h>

-#define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
-#define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
-
#define arch_spin_relax(lock) cpu_relax()
#define arch_read_relax(lock) cpu_relax()
#define arch_write_relax(lock) cpu_relax()
diff --git a/arch/parisc/include/asm/spinlock.h b/arch/parisc/include/asm/spinlock.h
index fa5ee8a45dbd..a6e5d66a7656 100644
--- a/arch/parisc/include/asm/spinlock.h
+++ b/arch/parisc/include/asm/spinlock.h
@@ -23,21 +23,6 @@ static inline void arch_spin_lock(arch_spinlock_t *x)
continue;
}

-static inline void arch_spin_lock_flags(arch_spinlock_t *x,
- unsigned long flags)
-{
- volatile unsigned int *a;
-
- a = __ldcw_align(x);
- while (__ldcw(a) == 0)
- while (*a == 0)
- if (flags & PSW_SM_I) {
- local_irq_enable();
- local_irq_disable();
- }
-}
-#define arch_spin_lock_flags arch_spin_lock_flags
-
static inline void arch_spin_unlock(arch_spinlock_t *x)
{
volatile unsigned int *a;
diff --git a/arch/powerpc/include/asm/simple_spinlock.h b/arch/powerpc/include/asm/simple_spinlock.h
index 8985791a2ba5..7ae6aeef8464 100644
--- a/arch/powerpc/include/asm/simple_spinlock.h
+++ b/arch/powerpc/include/asm/simple_spinlock.h
@@ -123,27 +123,6 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
}
}

-static inline
-void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
-{
- unsigned long flags_dis;
-
- while (1) {
- if (likely(__arch_spin_trylock(lock) == 0))
- break;
- local_save_flags(flags_dis);
- local_irq_restore(flags);
- do {
- HMT_low();
- if (is_shared_processor())
- splpar_spin_yield(lock);
- } while (unlikely(lock->slock != 0));
- HMT_medium();
- local_irq_restore(flags_dis);
- }
-}
-#define arch_spin_lock_flags arch_spin_lock_flags
-
static inline void arch_spin_unlock(arch_spinlock_t *lock)
{
__asm__ __volatile__("# arch_spin_unlock\n\t"
diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
index ef59588a3042..888a2f1c9ee3 100644
--- a/arch/s390/include/asm/spinlock.h
+++ b/arch/s390/include/asm/spinlock.h
@@ -67,14 +67,6 @@ static inline void arch_spin_lock(arch_spinlock_t *lp)
arch_spin_lock_wait(lp);
}

-static inline void arch_spin_lock_flags(arch_spinlock_t *lp,
- unsigned long flags)
-{
- if (!arch_spin_trylock_once(lp))
- arch_spin_lock_wait(lp);
-}
-#define arch_spin_lock_flags arch_spin_lock_flags
-
static inline int arch_spin_trylock(arch_spinlock_t *lp)
{
if (!arch_spin_trylock_once(lp))
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 9fe165beb0f9..467b94257105 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -481,23 +481,6 @@ do { \

#endif /* CONFIG_LOCK_STAT */

-#ifdef CONFIG_LOCKDEP
-
-/*
- * On lockdep we dont want the hand-coded irq-enable of
- * _raw_*_lock_flags() code, because lockdep assumes
- * that interrupts are not re-enabled during lock-acquire:
- */
-#define LOCK_CONTENDED_FLAGS(_lock, try, lock, lockfl, flags) \
- LOCK_CONTENDED((_lock), (try), (lock))
-
-#else /* CONFIG_LOCKDEP */
-
-#define LOCK_CONTENDED_FLAGS(_lock, try, lock, lockfl, flags) \
- lockfl((_lock), (flags))
-
-#endif /* CONFIG_LOCKDEP */
-
#ifdef CONFIG_PROVE_LOCKING
extern void print_irqtrace_events(struct task_struct *curr);
#else
diff --git a/include/linux/rwlock.h b/include/linux/rwlock.h
index 7ce9a51ae5c0..2c0ad417ce3c 100644
--- a/include/linux/rwlock.h
+++ b/include/linux/rwlock.h
@@ -30,31 +30,16 @@ do { \

#ifdef CONFIG_DEBUG_SPINLOCK
extern void do_raw_read_lock(rwlock_t *lock) __acquires(lock);
-#define do_raw_read_lock_flags(lock, flags) do_raw_read_lock(lock)
extern int do_raw_read_trylock(rwlock_t *lock);
extern void do_raw_read_unlock(rwlock_t *lock) __releases(lock);
extern void do_raw_write_lock(rwlock_t *lock) __acquires(lock);
-#define do_raw_write_lock_flags(lock, flags) do_raw_write_lock(lock)
extern int do_raw_write_trylock(rwlock_t *lock);
extern void do_raw_write_unlock(rwlock_t *lock) __releases(lock);
#else
-
-#ifndef arch_read_lock_flags
-# define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
-#endif
-
-#ifndef arch_write_lock_flags
-# define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
-#endif
-
# define do_raw_read_lock(rwlock) do {__acquire(lock); arch_read_lock(&(rwlock)->raw_lock); } while (0)
-# define do_raw_read_lock_flags(lock, flags) \
- do {__acquire(lock); arch_read_lock_flags(&(lock)->raw_lock, *(flags)); } while (0)
# define do_raw_read_trylock(rwlock) arch_read_trylock(&(rwlock)->raw_lock)
# define do_raw_read_unlock(rwlock) do {arch_read_unlock(&(rwlock)->raw_lock); __release(lock); } while (0)
# define do_raw_write_lock(rwlock) do {__acquire(lock); arch_write_lock(&(rwlock)->raw_lock); } while (0)
-# define do_raw_write_lock_flags(lock, flags) \
- do {__acquire(lock); arch_write_lock_flags(&(lock)->raw_lock, *(flags)); } while (0)
# define do_raw_write_trylock(rwlock) arch_write_trylock(&(rwlock)->raw_lock)
# define do_raw_write_unlock(rwlock) do {arch_write_unlock(&(rwlock)->raw_lock); __release(lock); } while (0)
#endif
diff --git a/include/linux/rwlock_api_smp.h b/include/linux/rwlock_api_smp.h
index abfb53ab11be..f1db6f17c4fb 100644
--- a/include/linux/rwlock_api_smp.h
+++ b/include/linux/rwlock_api_smp.h
@@ -157,8 +157,7 @@ static inline unsigned long __raw_read_lock_irqsave(rwlock_t *lock)
local_irq_save(flags);
preempt_disable();
rwlock_acquire_read(&lock->dep_map, 0, 0, _RET_IP_);
- LOCK_CONTENDED_FLAGS(lock, do_raw_read_trylock, do_raw_read_lock,
- do_raw_read_lock_flags, &flags);
+ LOCK_CONTENDED(lock, do_raw_read_trylock, do_raw_read_lock);
return flags;
}

@@ -184,8 +183,7 @@ static inline unsigned long __raw_write_lock_irqsave(rwlock_t *lock)
local_irq_save(flags);
preempt_disable();
rwlock_acquire(&lock->dep_map, 0, 0, _RET_IP_);
- LOCK_CONTENDED_FLAGS(lock, do_raw_write_trylock, do_raw_write_lock,
- do_raw_write_lock_flags, &flags);
+ LOCK_CONTENDED(lock, do_raw_write_trylock, do_raw_write_lock);
return flags;
}

diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
index c04e99edfe92..40e467cdee2d 100644
--- a/include/linux/spinlock.h
+++ b/include/linux/spinlock.h
@@ -176,7 +176,6 @@ do { \

#ifdef CONFIG_DEBUG_SPINLOCK
extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
-#define do_raw_spin_lock_flags(lock, flags) do_raw_spin_lock(lock)
extern int do_raw_spin_trylock(raw_spinlock_t *lock);
extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
#else
@@ -187,18 +186,6 @@ static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
mmiowb_spin_lock();
}

-#ifndef arch_spin_lock_flags
-#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
-#endif
-
-static inline void
-do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)
-{
- __acquire(lock);
- arch_spin_lock_flags(&lock->raw_lock, *flags);
- mmiowb_spin_lock();
-}
-
static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
{
int ret = arch_spin_trylock(&(lock)->raw_lock);
diff --git a/include/linux/spinlock_api_smp.h b/include/linux/spinlock_api_smp.h
index 6b8e1a0b137b..51fa0dab68c4 100644
--- a/include/linux/spinlock_api_smp.h
+++ b/include/linux/spinlock_api_smp.h
@@ -108,16 +108,7 @@ static inline unsigned long __raw_spin_lock_irqsave(raw_spinlock_t *lock)
local_irq_save(flags);
preempt_disable();
spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
- /*
- * On lockdep we dont want the hand-coded irq-enable of
- * do_raw_spin_lock_flags() code, because lockdep assumes
- * that interrupts are not re-enabled during lock-acquire:
- */
-#ifdef CONFIG_LOCKDEP
LOCK_CONTENDED(lock, do_raw_spin_trylock, do_raw_spin_lock);
-#else
- do_raw_spin_lock_flags(lock, &flags);
-#endif
return flags;
}

diff --git a/include/linux/spinlock_up.h b/include/linux/spinlock_up.h
index 0ac9112c1bbe..16521074b6f7 100644
--- a/include/linux/spinlock_up.h
+++ b/include/linux/spinlock_up.h
@@ -62,7 +62,6 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
#define arch_spin_is_locked(lock) ((void)(lock), 0)
/* for sched/core.c and kernel_lock.c: */
# define arch_spin_lock(lock) do { barrier(); (void)(lock); } while (0)
-# define arch_spin_lock_flags(lock, flags) do { barrier(); (void)(lock); } while (0)
# define arch_spin_unlock(lock) do { barrier(); (void)(lock); } while (0)
# define arch_spin_trylock(lock) ({ barrier(); (void)(lock); 1; })
#endif /* DEBUG_SPINLOCK */
diff --git a/kernel/locking/spinlock.c b/kernel/locking/spinlock.c
index c5830cfa379a..b562f9289372 100644
--- a/kernel/locking/spinlock.c
+++ b/kernel/locking/spinlock.c
@@ -378,8 +378,7 @@ unsigned long __lockfunc _raw_spin_lock_irqsave_nested(raw_spinlock_t *lock,
local_irq_save(flags);
preempt_disable();
spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
- LOCK_CONTENDED_FLAGS(lock, do_raw_spin_trylock, do_raw_spin_lock,
- do_raw_spin_lock_flags, &flags);
+ LOCK_CONTENDED(lock, do_raw_spin_trylock, do_raw_spin_lock);
return flags;
}
EXPORT_SYMBOL(_raw_spin_lock_irqsave_nested);
--
2.29.2