Hi, Baibir
sorry for late responce, I missed reading your mail.
在 16/7/6 18:54, Balbir Singh 写道:
On Tue, 2016-06-28 at 10:43 -0400, Pan Xinhui wrote:
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 take the cpu
^^ takes
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.
As kernel has used this interface, So lets support it.
Only pSeries need supoort it. And the fact is powerNV are built into same
^^ support
kernel image with pSeries. So we need return false if we are runnig as
powerNV. The another fact is that lppaca->yiled_count keeps zero on
^^ yield
powerNV. So we can just skip the machine type.
Blame on me, I indeed need avoid such typo..
thanks for pointing it out.
Suggested-by: Boqun Feng <boqun.feng@xxxxxxxxx>
Suggested-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Pan Xinhui <xinhui.pan@xxxxxxxxxxxxxxxxxx>
---
arch/powerpc/include/asm/spinlock.h | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h
index 523673d..3ac9fcb 100644
--- a/arch/powerpc/include/asm/spinlock.h
+++ b/arch/powerpc/include/asm/spinlock.h
@@ -52,6 +52,24 @@
#define SYNC_IO
#endif
+/*
+ * This support kernel to check if one cpu is preempted or not.
+ * Then we can fix some lock holder preemption issue.
+ */
+#ifdef CONFIG_PPC_PSERIES
+#define vcpu_is_preempted vcpu_is_preempted
+static inline bool vcpu_is_preempted(int cpu)
+{
+ /*
+ * pSeries and powerNV can be built into same kernel image. In
+ * principle we need return false directly if we are running as
+ * powerNV. However the yield_count is always zero on powerNV, So
+ * skip such machine type check
Or you could use the ppc_md interface callbacks if required, but your
solution works as well
thanks, So I can keep my code as is.
thanks
xinhui
+ */
+ return !!(be32_to_cpu(lppaca_of(cpu).yield_count) & 1);
+}
+#endif
+
static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
{
return lock.slock == 0;
Balbir Singh.
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