s390/cpum_cf: prepare for in-kernel counter measurements

Prepare the counter facility support to be used by other in-kernel
users.  The first step introduces the __kernel_cpumcf_begin() and
__kernel_cpumcf_end() functions to reserve the counter facility
for doing measurements and to release after the measurements are
done.

Signed-off-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/include/asm/cpu_mcf.h b/arch/s390/include/asm/cpu_mcf.h
index b6e73fb..63fa741 100644 (file)
--- a/arch/s390/include/asm/cpu_mcf.h
+++ b/arch/s390/include/asm/cpu_mcf.h
@@ -49,4 +49,7 @@ static inline void ctr_set_stop(u64 *state, int ctr_set)
        *state &= ~(cpumf_ctr_ctl[ctr_set] << CPUMF_LCCTL_ACTCTL_SHIFT);
 }
 
+int __kernel_cpumcf_begin(void);
+void __kernel_cpumcf_end(void);
+
 #endif /* _ASM_S390_CPU_MCF_H */

diff --git a/arch/s390/kernel/perf_cpum_cf.c b/arch/s390/kernel/perf_cpum_cf.c
index 66d945d..b2e46b8 100644 (file)
--- a/arch/s390/kernel/perf_cpum_cf.c
+++ b/arch/s390/kernel/perf_cpum_cf.c
@@ -236,25 +236,45 @@ static void setup_pmc_cpu(void *flags)
        lcctl(0);
 }
 
-/* Initialize the CPU-measurement facility */
-static int reserve_pmc_hardware(void)
+/* Reserve/release functions for sharing perf hardware */
+static DEFINE_SPINLOCK(cpumcf_owner_lock);
+static void *cpumcf_owner;
+
+/* Initialize the CPU-measurement counter facility */
+int __kernel_cpumcf_begin(void)
 {
        int flags = PMC_INIT;
+       int err = 0;
+
+       spin_lock(&cpumcf_owner_lock);
+       if (cpumcf_owner)
+               err = -EBUSY;
+       else
+               cpumcf_owner = __builtin_return_address(0);
+       spin_unlock(&cpumcf_owner_lock);
+       if (err)
+               return err;
 
        on_each_cpu(setup_pmc_cpu, &flags, 1);
        irq_subclass_register(IRQ_SUBCLASS_MEASUREMENT_ALERT);
 
        return 0;
 }
+EXPORT_SYMBOL(__kernel_cpumcf_begin);
 
-/* Release the CPU-measurement facility */
-static void release_pmc_hardware(void)
+/* Release the CPU-measurement counter facility */
+void __kernel_cpumcf_end(void)
 {
        int flags = PMC_RELEASE;
 
        on_each_cpu(setup_pmc_cpu, &flags, 1);
        irq_subclass_unregister(IRQ_SUBCLASS_MEASUREMENT_ALERT);
+
+       spin_lock(&cpumcf_owner_lock);
+       cpumcf_owner = NULL;
+       spin_unlock(&cpumcf_owner_lock);
 }
+EXPORT_SYMBOL(__kernel_cpumcf_end);
 
 /* Release the PMU if event is the last perf event */
 static void hw_perf_event_destroy(struct perf_event *event)
@@ -262,7 +282,7 @@ static void hw_perf_event_destroy(struct perf_event *event)
        if (!atomic_add_unless(&num_events, -1, 1)) {
                mutex_lock(&pmc_reserve_mutex);
                if (atomic_dec_return(&num_events) == 0)
-                       release_pmc_hardware();
+                       __kernel_cpumcf_end();
                mutex_unlock(&pmc_reserve_mutex);
        }
 }
@@ -363,7 +383,7 @@ static int __hw_perf_event_init(struct perf_event *event)
        /* Initialize for using the CPU-measurement counter facility */
        if (!atomic_inc_not_zero(&num_events)) {
                mutex_lock(&pmc_reserve_mutex);
-               if (atomic_read(&num_events) == 0 && reserve_pmc_hardware())
+               if (atomic_read(&num_events) == 0 && __kernel_cpumcf_begin())
                        err = -EBUSY;
                else
                        atomic_inc(&num_events);