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O(1) scheduler fix for 2.5-ia64

PATCH Erich Focht 1 participant 1 message Nov 4, 2002

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Erich Focht

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Hi David,

this problem is wellknown and I actually thought that it was solved. But it looks like the complex prepare_arch_switch() etc. macros didn't make it into the 2.5 kernels for IA64. They are needed on IA64 because we have to release the runqueue lock during context switch. This is similar to sparc64. Thanks to John Hawks for noticing this.

Please include this into your kernel tree.

Regards,
Erich

include/asm-ia64/system.h +12 -0
diff -urNp linux-2.5.45-ia64/include/asm-ia64/system.h linux-2.5.45-ia64-o1fix/include/asm-ia64/system.h
@@ -432,6 +432,18 @@ extern void ia64_load_extra (struct task
 } while (0)
 #endif
 
+#define prepare_arch_switch(rq, next)		\
+do {	spin_lock(&(next)->switch_lock);	\
+	spin_unlock(&(rq)->lock);		\
+} while (0)
+
+#define finish_arch_switch(rq, prev)		\
+do {	spin_unlock_irq(&(prev)->switch_lock);	\
+} while (0)
+
+#define task_running(rq, p) \
+	((rq)->curr == (p) || spin_is_locked(&(p)->switch_lock))
+
 #endif /* __KERNEL__ */
 
 #endif /* __ASSEMBLY__ */