powerpc: Provide a way to defer perf counter work until interrupts are enabled
Because 64-bit powerpc uses lazy (soft) interrupt disabling, it is
possible for a performance monitor exception to come in when the
kernel thinks interrupts are disabled (i.e. when they are
soft-disabled but hard-enabled). In such a situation the performance
monitor exception handler might have some processing to do (such as
process wakeups) which can't be done in what is effectively an NMI
handler.
This provides a way to defer that work until interrupts get enabled,
either in raw_local_irq_restore() or by returning from an interrupt
handler to code that had interrupts enabled. We have a per-processor
flag that indicates that there is work pending to do when interrupts
subsequently get re-enabled. This flag is checked in the interrupt
return path and in raw_local_irq_restore(), and if it is set,
perf_counter_do_pending() is called to do the pending work.
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
index f75a5fc..e10f151 100644
--- a/arch/powerpc/include/asm/hw_irq.h
+++ b/arch/powerpc/include/asm/hw_irq.h
@@ -131,5 +131,36 @@
*/
struct hw_interrupt_type;
+#ifdef CONFIG_PERF_COUNTERS
+static inline unsigned long get_perf_counter_pending(void)
+{
+ unsigned long x;
+
+ asm volatile("lbz %0,%1(13)"
+ : "=r" (x)
+ : "i" (offsetof(struct paca_struct, perf_counter_pending)));
+ return x;
+}
+
+static inline void set_perf_counter_pending(int x)
+{
+ asm volatile("stb %0,%1(13)" : :
+ "r" (x),
+ "i" (offsetof(struct paca_struct, perf_counter_pending)));
+}
+
+extern void perf_counter_do_pending(void);
+
+#else
+
+static inline unsigned long get_perf_counter_pending(void)
+{
+ return 0;
+}
+
+static inline void set_perf_counter_pending(int x) {}
+static inline void perf_counter_do_pending(void) {}
+#endif /* CONFIG_PERF_COUNTERS */
+
#endif /* __KERNEL__ */
#endif /* _ASM_POWERPC_HW_IRQ_H */