oprofile, x86: Reimplement nmi timer mode using perf event

The legacy x86 nmi watchdog code was removed with the implementation
of the perf based nmi watchdog. This broke Oprofile's nmi timer
mode. To run nmi timer mode we relied on a continuous ticking nmi
source which the nmi watchdog provided. The nmi tick was no longer
available and current watchdog can not be used anymore since it runs
with very long periods in the range of seconds. This patch
reimplements the nmi timer mode using a perf counter nmi source.

V2:
* removing pr_info()
* fix undefined reference to `__udivdi3' for 32 bit build
* fix section mismatch of .cpuinit.data:nmi_timer_cpu_nb
* removed nmi timer setup in arch/x86
* implemented function stubs for op_nmi_init/exit()
* made code more readable in oprofile_init()

V3:
* fix architectural initialization in oprofile_init()
* fix CONFIG_OPROFILE_NMI_TIMER dependencies

Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Robert Richter <robert.richter@amd.com>

1 files changed, 11 insertions, 13 deletions

diff --git a/drivers/oprofile/oprof.c b/drivers/oprofile/oprof.c
index f7cd06967ae..ed2c3ec0702 100644
--- a/drivers/oprofile/oprof.c
+++ b/drivers/oprofile/oprof.c
@@ -246,26 +246,24 @@ static int __init oprofile_init(void)
         int err;
 
         /* always init architecture to setup backtrace support */
+        timer_mode = 0;
         err = oprofile_arch_init(&oprofile_ops);
+        if (!err) {
+                if (!timer && !oprofilefs_register())
+                        return 0;
+                oprofile_arch_exit();
+        }
 
-        timer_mode = err || timer;      /* fall back to timer mode on errors */
-        if (timer_mode) {
-                if (!err)
-                        oprofile_arch_exit();
+        /* setup timer mode: */
+        timer_mode = 1;
+        /* no nmi timer mode if oprofile.timer is set */
+        if (timer || op_nmi_timer_init(&oprofile_ops)) {
                 err = oprofile_timer_init(&oprofile_ops);
                 if (err)
                         return err;
         }
 
-        err = oprofilefs_register();
-        if (!err)
-                return 0;
-
-        /* failed */
-        if (!timer_mode)
-                oprofile_arch_exit();
-
-        return err;
+        return oprofilefs_register();
 }