On 2016年06月27日 16:42, Peter Zijlstra wrote:
On Sun, Jun 26, 2016 at 06:41:54AM -0400, Pan Xinhui wrote:
+#ifdef arch_vcpu_is_preempted
+static inline bool vcpu_is_preempted(int cpu)
+{
+ return arch_vcpu_is_preempted(cpu);
+}
+#else
+static inline bool vcpu_is_preempted(int cpu)
+{
+ return 0;
+}
+#endif
+
+#ifdef arch_vcpu_get_yield_count
+static inline unsigned int vcpu_get_yield_count(int cpu)
+{
+ return arch_vcpu_get_yield_count(cpu);
+}
+#else
+static inline unsigned int vcpu_get_yield_count(int cpu)
+{
+ return 0;
+}
+#endif
Please, just do something like:
#ifndef vcpu_is_preempted
static inline bool vcpu_is_preempted(int cpu)
{
return false;
}
#endif
No point in making it more complicated.
right, vcpu_is_preempted() is good enough to handle our osq issue.
+static inline bool
+need_yield_to(int vcpu, unsigned int old_yield_count)
namespace... this thing should be called: vcpu_something()
+{
+ /* if we find the vcpu is preempted,
+ * then we may want to kick it, IOW, yield to it
+ */
+ return vcpu_is_preempted(vcpu) ||
+ (vcpu_get_yield_count(vcpu) != old_yield_count);
+}
And can you make doubly sure (and mention in the Changelog) that the OSQ
code compiles all this away when using these definitions.
vimdiff shows the osq_lock.o has a little difference because osq read the
yield_count and prev, even they are not used.
however, as you suggest above, IF I remove the vcpu_get_yield_count() and
relevant code in osq_lock, then the binary is same.
