perfmon2 minimal: X86 OProfile hooks

Index: o/arch/x86/oprofile/nmi_int.c
===================================================================
@@ -15,6 +15,7 @@
 #include <linux/slab.h>
 #include <linux/moduleparam.h>
 #include <linux/kdebug.h>
+#include <linux/perfmon_kern.h>
 #include <asm/nmi.h>
 #include <asm/msr.h>
 #include <asm/apic.h>

@@ -191,12 +192,18 @@
 	int err = 0;
 	int cpu;
 
-	if (!allocate_msrs())
+	if (pfm_session_allcpus_acquire())
+		return -EBUSY;
+
+	if (!allocate_msrs()) {
+		pfm_session_allcpus_release();
 		return -ENOMEM;
+	}
 
 	err = register_die_notifier(&profile_exceptions_nb);
 	if (err) {
 		free_msrs();
+		pfm_session_allcpus_release();
 		return err;
 	}
 

@@ -275,6 +282,7 @@
 	unregister_die_notifier(&profile_exceptions_nb);
 	model->shutdown(msrs);
 	free_msrs();
+	pfm_session_allcpus_release();
 }
 
 static void nmi_cpu_start(void *dummy)

Index: o/include/linux/perfmon_kern.h
===================================================================
@@ -180,6 +180,9 @@
 
 void pfm_interrupt_handler(unsigned long ip, struct pt_regs *regs);
 
+int pfm_session_allcpus_acquire(void);
+void pfm_session_allcpus_release(void);
+
 static inline void pfm_exit_thread(void)
 {
 	if (current->pfm_context)

@@ -256,6 +259,8 @@
 #define pfm_copy_thread(_t)		do { } while (0)
 #define pfm_ctxsw_in(_p, _n)    	do { } while (0)
 #define pfm_ctxsw_out(_p, _n)      	do { } while (0)
+#define pfm_session_allcpus_release()	do { } while (0)
+#define pfm_session_allcpus_acquire()	(0)
 
 #endif /* CONFIG_PERFMON */
 

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