[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>
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 3979a6f..b3461e8 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 @@
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 @@
#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 @@
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 @@
#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();