--- v6
+++ v5
@@ -1,152 +1,79 @@
-From: Christian Borntraeger <borntraeger@de.ibm.com>
+This is to fix some lock holder preemption issues. Some other locks
+implementation do a spin loop before acquiring the lock itself.
+Currently kernel has an interface of bool vcpu_is_preempted(int cpu). It
+takes the cpu as parameter and return true if the cpu is preempted.
+Then kernel can break the spin loops upon on the retval of
+vcpu_is_preempted.
-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.
+As kernel has used this interface, So lets support it.
-Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
-Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
+To deal with kernel and kvm/xen, add vcpu_is_preempted into struct
+pv_lock_ops.
+
+Then kvm or xen could provide their own implementation to support
+vcpu_is_preempted.
+
+Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
---
- arch/s390/include/asm/spinlock.h | 8 ++++++++
- arch/s390/kernel/smp.c | 9 +++++++--
- arch/s390/lib/spinlock.c | 25 ++++++++-----------------
- 3 files changed, 23 insertions(+), 19 deletions(-)
+ arch/x86/include/asm/paravirt_types.h | 2 ++
+ arch/x86/include/asm/spinlock.h | 8 ++++++++
+ arch/x86/kernel/paravirt-spinlocks.c | 6 ++++++
+ 3 files changed, 16 insertions(+)
-diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
-index 7e9e09f..7ecd890 100644
---- a/arch/s390/include/asm/spinlock.h
-+++ b/arch/s390/include/asm/spinlock.h
-@@ -23,6 +23,14 @@ _raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new)
- return __sync_bool_compare_and_swap(lock, old, new);
+diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
+index 0f400c0..38c3bb7 100644
+--- a/arch/x86/include/asm/paravirt_types.h
++++ b/arch/x86/include/asm/paravirt_types.h
+@@ -310,6 +310,8 @@ struct pv_lock_ops {
+
+ void (*wait)(u8 *ptr, u8 val);
+ void (*kick)(int cpu);
++
++ bool (*vcpu_is_preempted)(int cpu);
+ };
+
+ /* This contains all the paravirt structures: we get a convenient
+diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h
+index 921bea7..0526f59 100644
+--- a/arch/x86/include/asm/spinlock.h
++++ b/arch/x86/include/asm/spinlock.h
+@@ -26,6 +26,14 @@
+ extern struct static_key paravirt_ticketlocks_enabled;
+ static __always_inline bool static_key_false(struct static_key *key);
+
++#ifdef CONFIG_PARAVIRT_SPINLOCKS
++#define vcpu_is_preempted vcpu_is_preempted
++static inline bool vcpu_is_preempted(int cpu)
++{
++ return pv_lock_ops.vcpu_is_preempted(cpu);
++}
++#endif
++
+ #include <asm/qspinlock.h>
+
+ /*
+diff --git a/arch/x86/kernel/paravirt-spinlocks.c b/arch/x86/kernel/paravirt-spinlocks.c
+index 2c55a00..2f204dd 100644
+--- a/arch/x86/kernel/paravirt-spinlocks.c
++++ b/arch/x86/kernel/paravirt-spinlocks.c
+@@ -21,12 +21,18 @@ bool pv_is_native_spin_unlock(void)
+ __raw_callee_save___native_queued_spin_unlock;
}
-+#ifndef CONFIG_SMP
-+static inline bool arch_vcpu_is_preempted(int cpu) { return false; }
-+#else
-+bool arch_vcpu_is_preempted(int cpu);
-+#endif
++static bool native_vcpu_is_preempted(int cpu)
++{
++ return 0;
++}
+
-+#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 35531fe..b988ed1 100644
---- a/arch/s390/kernel/smp.c
-+++ b/arch/s390/kernel/smp.c
-@@ -368,10 +368,15 @@ int smp_find_processor_id(u16 address)
- return -1;
- }
-
--int smp_vcpu_scheduled(int 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;
-+ 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);
- }
+ struct pv_lock_ops pv_lock_ops = {
+ #ifdef CONFIG_SMP
+ .queued_spin_lock_slowpath = native_queued_spin_lock_slowpath,
+ .queued_spin_unlock = PV_CALLEE_SAVE(__native_queued_spin_unlock),
+ .wait = paravirt_nop,
+ .kick = paravirt_nop,
++ .vcpu_is_preempted = native_vcpu_is_preempted,
+ #endif /* SMP */
+ };
+ EXPORT_SYMBOL(pv_lock_ops);
--
2.4.11