[PATCH] fast vdso implementation for CLOCK_THREAD_CPUTIME_ID

The extract cpu time instruction (ectg) instruction allows the user
process to get the current thread cputime without calling into the
kernel. The code that uses the instruction needs to switch to the
access registers mode to get access to the per-cpu info page that
contains the two base values that are needed to calculate the current
cputime from the CPU timer with the ectg instruction.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 3979a6fc0882..b3461e8f1705 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -47,6 +47,7 @@
 #include <asm/lowcore.h>
 #include <asm/sclp.h>
 #include <asm/cpu.h>
+#include <asm/vdso.h>
 #include "entry.h"
 
 /*
@@ -506,6 +507,9 @@ static int __cpuinit smp_alloc_lowcore(int cpu)
                         goto out;
                 lowcore->extended_save_area_addr = (u32) save_area;
         }
+#else
+        if (vdso_alloc_per_cpu(cpu, lowcore))
+                goto out;
 #endif
         lowcore_ptr[cpu] = lowcore;
         return 0;
@@ -528,6 +532,8 @@ static void smp_free_lowcore(int cpu)
 #ifndef CONFIG_64BIT
         if (MACHINE_HAS_IEEE)
                 free_page((unsigned long) lowcore->extended_save_area_addr);
+#else
+        vdso_free_per_cpu(cpu, lowcore);
 #endif
         free_page(lowcore->panic_stack - PAGE_SIZE);
         free_pages(lowcore->async_stack - ASYNC_SIZE, ASYNC_ORDER);
@@ -670,6 +676,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
         lowcore = (void *) __get_free_pages(GFP_KERNEL | GFP_DMA, lc_order);
         panic_stack = __get_free_page(GFP_KERNEL);
         async_stack = __get_free_pages(GFP_KERNEL, ASYNC_ORDER);
+        BUG_ON(!lowcore || !panic_stack || !async_stack);
 #ifndef CONFIG_64BIT
         if (MACHINE_HAS_IEEE)
                 save_area = get_zeroed_page(GFP_KERNEL);
@@ -683,6 +690,8 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
 #ifndef CONFIG_64BIT
         if (MACHINE_HAS_IEEE)
                 lowcore->extended_save_area_addr = (u32) save_area;
+#else
+        BUG_ON(vdso_alloc_per_cpu(smp_processor_id(), lowcore));
 #endif
         set_prefix((u32)(unsigned long) lowcore);
         local_mcck_enable();