Re: [PATCH v2 1/1] s390/spinlock: Provide vcpu_is_preempted
From: Pan Xinhui
Date: Fri Sep 30 2016 - 02:36:04 EST
å 2016/9/30 13:52, Boqun Feng åé:
On Fri, Sep 30, 2016 at 12:49:52PM +0800, Pan Xinhui wrote:
å 2016/9/29 23:51, Christian Borntraeger åé:
this implements the s390 backend for commit
"kernel/sched: introduce vcpu preempted check interface"
by reworking the existing smp_vcpu_scheduled into
arch_vcpu_is_preempted. We can then also get rid of the
local cpu_is_preempted function by moving the
CIF_ENABLED_WAIT test into arch_vcpu_is_preempted.
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
hi, Christian
thanks for your patch!
arch/s390/include/asm/spinlock.h | 3 +++
arch/s390/kernel/smp.c | 9 +++++++--
arch/s390/lib/spinlock.c | 25 ++++++++-----------------
3 files changed, 18 insertions(+), 19 deletions(-)
diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
index 63ebf37..e16e02f 100644
--- a/arch/s390/include/asm/spinlock.h
+++ b/arch/s390/include/asm/spinlock.h
@@ -21,6 +21,9 @@ _raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new)
return __sync_bool_compare_and_swap(lock, old, new);
}
+bool arch_vcpu_is_preempted(int cpu);
+#define vcpu_is_preempted arch_vcpu_is_preempted
+
/*
* Simple spin lock operations. There are two variants, one clears IRQ's
* on the local processor, one does not.
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 7b89a75..4aadd16 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -376,10 +376,15 @@ int smp_find_processor_id(u16 address)
return -1;
}
-int smp_vcpu_scheduled(int cpu)
root@ltcalpine2-lp13:~/linux# git grep -wn smp_vcpu_scheduled arch/s390/
arch/s390/include/asm/smp.h:34:extern int smp_vcpu_scheduled(int cpu);
arch/s390/include/asm/smp.h:56:static inline int smp_vcpu_scheduled(int cpu) { return 1; }
arch/s390/kernel/smp.c:371:int smp_vcpu_scheduled(int cpu)
arch/s390/lib/spinlock.c:44: if (smp_vcpu_scheduled(cpu))
+bool arch_vcpu_is_preempted(int cpu)
{
- return pcpu_running(pcpu_devices + cpu);
+ if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
+ return false;
+ if (pcpu_running(pcpu_devices + cpu))
+ return false;
I saw smp_vcpu_scheduled() returns true always on !SMP system.
maybe we can do somegthing silimar. like below
#ifndef CONFIG_SMP
static inline bool arch_vcpu_is_preempted(int cpu) { return !test_cpu_flag_of(CIF_ENABLED_WAIT, cpu); }
#else
...
but I can't help thinking that if this is a!SMP system, maybe we could only
#ifndef CONFIG_SMP
static inline bool arch_vcpu_is_preempted(int cpu) { return false; }
#else
Why do we need a vcpu_is_preempted() implementation for UP? Where will
you use it?
yep, I also wonder that :)
But there is a definitaion of smp_vcpu_scheduled() for !SMP kernel.
So I am a little worried that some code has included this spinlock.h for UP kernel also.
Hi, Christian
Could you help confirms that your patch works on UP? :)
thanks
xinhui
Regards,
Boqun
...
thanks
xinhui
+ return true;
}
+EXPORT_SYMBOL(arch_vcpu_is_preempted);
void smp_yield_cpu(int cpu)
{
diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index e5f50a7..e48a48e 100644
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -37,15 +37,6 @@ static inline void _raw_compare_and_delay(unsigned int *lock, unsigned int old)
asm(".insn rsy,0xeb0000000022,%0,0,%1" : : "d" (old), "Q" (*lock));
}
-static inline int cpu_is_preempted(int cpu)
-{
- if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
- return 0;
- if (smp_vcpu_scheduled(cpu))
- return 0;
- return 1;
-}
-
void arch_spin_lock_wait(arch_spinlock_t *lp)
{
unsigned int cpu = SPINLOCK_LOCKVAL;
@@ -62,7 +53,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
continue;
}
/* First iteration: check if the lock owner is running. */
- if (first_diag && cpu_is_preempted(~owner)) {
+ if (first_diag && arch_vcpu_is_preempted(~owner)) {
smp_yield_cpu(~owner);
first_diag = 0;
continue;
@@ -81,7 +72,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
* yield the CPU unconditionally. For LPAR rely on the
* sense running status.
*/
- if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
+ if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(~owner)) {
smp_yield_cpu(~owner);
first_diag = 0;
}
@@ -108,7 +99,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
continue;
}
/* Check if the lock owner is running. */
- if (first_diag && cpu_is_preempted(~owner)) {
+ if (first_diag && arch_vcpu_is_preempted(~owner)) {
smp_yield_cpu(~owner);
first_diag = 0;
continue;
@@ -127,7 +118,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
* yield the CPU unconditionally. For LPAR rely on the
* sense running status.
*/
- if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
+ if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(~owner)) {
smp_yield_cpu(~owner);
first_diag = 0;
}
@@ -165,7 +156,7 @@ void _raw_read_lock_wait(arch_rwlock_t *rw)
owner = 0;
while (1) {
if (count-- <= 0) {
- if (owner && cpu_is_preempted(~owner))
+ if (owner && arch_vcpu_is_preempted(~owner))
smp_yield_cpu(~owner);
count = spin_retry;
}
@@ -211,7 +202,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev)
owner = 0;
while (1) {
if (count-- <= 0) {
- if (owner && cpu_is_preempted(~owner))
+ if (owner && arch_vcpu_is_preempted(~owner))
smp_yield_cpu(~owner);
count = spin_retry;
}
@@ -241,7 +232,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw)
owner = 0;
while (1) {
if (count-- <= 0) {
- if (owner && cpu_is_preempted(~owner))
+ if (owner && arch_vcpu_is_preempted(~owner))
smp_yield_cpu(~owner);
count = spin_retry;
}
@@ -285,7 +276,7 @@ void arch_lock_relax(unsigned int cpu)
{
if (!cpu)
return;
- if (MACHINE_IS_LPAR && !cpu_is_preempted(~cpu))
+ if (MACHINE_IS_LPAR && !arch_vcpu_is_preempted(~cpu))
return;
smp_yield_cpu(~cpu);
}