summaryrefslogtreecommitdiff
path: root/arch/parisc
diff options
context:
space:
mode:
authorDave Anglin <dave.anglin@bell.net>2021-11-03 12:49:32 +0100
committerHelge Deller <deller@gmx.de>2021-11-04 11:21:20 +0100
commit7e992711dddbdb1c27d077432d8440fefd44819f (patch)
tree01208b85e053dda7deeb9eac8e3924f62b9ba144 /arch/parisc
parent014966dcf76bce5717f7d974d0410d3402a651c2 (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.h24
-rw-r--r--arch/parisc/kernel/syscall.S10
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 */