diff options
author | Dave Anglin <dave.anglin@bell.net> | 2021-11-03 12:49:32 +0100 |
---|---|---|
committer | Helge Deller <deller@gmx.de> | 2021-11-04 11:21:20 +0100 |
commit | 7e992711dddbdb1c27d077432d8440fefd44819f (patch) | |
tree | 01208b85e053dda7deeb9eac8e3924f62b9ba144 /arch/parisc | |
parent | 014966dcf76bce5717f7d974d0410d3402a651c2 (diff) |
parisc: Don't disable interrupts in cmpxchg and futex operations
I no longer think interrupts can be disabled in the futex and cmpxchg
operations because of COW breaks. This not ideal but I suspect it's the
best we can do.
For the cmpxchg operations in syscall.S, we rely on the code to not
schedule off the gateway page. For the futex, I added code to disable
preemption.
So far, I haven't seen the warnings with the attached change but the
change is only lightly tested.
Signed-off-by: Dave Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>
Diffstat (limited to 'arch/parisc')
-rw-r--r-- | arch/parisc/include/asm/futex.h | 24 | ||||
-rw-r--r-- | arch/parisc/kernel/syscall.S | 10 |
2 files changed, 11 insertions, 23 deletions
diff --git a/arch/parisc/include/asm/futex.h b/arch/parisc/include/asm/futex.h index e38a118cf65d..70cf8f0a7617 100644 --- a/arch/parisc/include/asm/futex.h +++ b/arch/parisc/include/asm/futex.h @@ -11,35 +11,34 @@ sixteen four-word locks. */ static inline void -_futex_spin_lock_irqsave(u32 __user *uaddr, unsigned long int *flags) +_futex_spin_lock(u32 __user *uaddr) { extern u32 lws_lock_start[]; long index = ((long)uaddr & 0x3f8) >> 1; arch_spinlock_t *s = (arch_spinlock_t *)&lws_lock_start[index]; - local_irq_save(*flags); + preempt_disable(); arch_spin_lock(s); } static inline void -_futex_spin_unlock_irqrestore(u32 __user *uaddr, unsigned long int *flags) +_futex_spin_unlock(u32 __user *uaddr) { extern u32 lws_lock_start[]; long index = ((long)uaddr & 0x3f8) >> 1; arch_spinlock_t *s = (arch_spinlock_t *)&lws_lock_start[index]; arch_spin_unlock(s); - local_irq_restore(*flags); + preempt_enable(); } static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr) { - unsigned long int flags; int oldval, ret; u32 tmp; - _futex_spin_lock_irqsave(uaddr, &flags); - ret = -EFAULT; + + _futex_spin_lock(uaddr); if (unlikely(get_user(oldval, uaddr) != 0)) goto out_pagefault_enable; @@ -70,7 +69,7 @@ arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr) ret = -EFAULT; out_pagefault_enable: - _futex_spin_unlock_irqrestore(uaddr, &flags); + _futex_spin_unlock(uaddr); if (!ret) *oval = oldval; @@ -83,7 +82,6 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 oldval, u32 newval) { u32 val; - unsigned long flags; /* futex.c wants to do a cmpxchg_inatomic on kernel NULL, which is * our gateway page, and causes no end of trouble... @@ -100,19 +98,19 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, * address. This should scale to a couple of CPUs. */ - _futex_spin_lock_irqsave(uaddr, &flags); + _futex_spin_lock(uaddr); if (unlikely(get_user(val, uaddr) != 0)) { - _futex_spin_unlock_irqrestore(uaddr, &flags); + _futex_spin_unlock(uaddr); return -EFAULT; } if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) { - _futex_spin_unlock_irqrestore(uaddr, &flags); + _futex_spin_unlock(uaddr); return -EFAULT; } *uval = val; - _futex_spin_unlock_irqrestore(uaddr, &flags); + _futex_spin_unlock(uaddr); return 0; } diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index ec9675f58435..4fb3b6a993bf 100644 --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -597,13 +597,11 @@ cas_nocontend: # endif /* ENABLE_LWS_DEBUG */ - rsm PSW_SM_I, %r0 /* Disable interrupts */ /* COW breaks can cause contention on UP systems */ LDCW 0(%sr2,%r20), %r28 /* Try to acquire the lock */ cmpb,<>,n %r0, %r28, cas_action /* Did we get it? */ cas_wouldblock: ldo 2(%r0), %r28 /* 2nd case */ - ssm PSW_SM_I, %r0 b lws_exit /* Contended... */ ldo -EAGAIN(%r0), %r21 /* Spin in userspace */ @@ -639,8 +637,6 @@ cas_action: /* Clear thread register indicator */ stw %r0, 4(%sr2,%r20) #endif - /* Enable interrupts */ - ssm PSW_SM_I, %r0 /* Return to userspace, set no error */ b lws_exit copy %r0, %r21 @@ -652,7 +648,6 @@ cas_action: #if ENABLE_LWS_DEBUG stw %r0, 4(%sr2,%r20) #endif - ssm PSW_SM_I, %r0 b lws_exit ldo -EFAULT(%r0),%r21 /* set errno */ nop @@ -764,13 +759,11 @@ cas2_lock_start: shlw %r20, 4, %r20 add %r20, %r28, %r20 - rsm PSW_SM_I, %r0 /* Disable interrupts */ /* COW breaks can cause contention on UP systems */ LDCW 0(%sr2,%r20), %r28 /* Try to acquire the lock */ cmpb,<>,n %r0, %r28, cas2_action /* Did we get it? */ cas2_wouldblock: ldo 2(%r0), %r28 /* 2nd case */ - ssm PSW_SM_I, %r0 b lws_exit /* Contended... */ ldo -EAGAIN(%r0), %r21 /* Spin in userspace */ @@ -850,8 +843,6 @@ cas2_action: cas2_end: /* Free lock */ stw,ma %r20, 0(%sr2,%r20) - /* Enable interrupts */ - ssm PSW_SM_I, %r0 /* Return to userspace, set no error */ b lws_exit copy %r0, %r21 @@ -860,7 +851,6 @@ cas2_end: /* Error occurred on load or store */ /* Free lock */ stw,ma %r20, 0(%sr2,%r20) - ssm PSW_SM_I, %r0 ldo 1(%r0),%r28 b lws_exit ldo -EFAULT(%r0),%r21 /* set errno */ |