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SubjectRe: 2.6.25-rc3-mm1 - PROFILE_LIKELY redux..
On Wed, 05 Mar 2008 18:45:13 +0100 Andi Kleen <andi@firstfloor.org> wrote:

> Valdis.Kletnieks@vt.edu writes:
> >
> > So we're in the same 4K as the VDSO64_* values, but some 0x4fe past the
> > gtod_data. Anybody got a hint as to what the heck it was doing?
>
> Try this patch:
>
> Remove unlikelies in vsyscall path
>
> Remove unlikely in vsyscall path that conflict with unlikely profiling.
> The unlikelies shouldn't be needed anyways because gcc predicts
> condition leading to early return as unlikely by default and
> for the loops it shouldn't make much difference
>
> --- linux.orig/arch/x86/kernel/vsyscall_64.c
> +++ linux/arch/x86/kernel/vsyscall_64.c
> ...
> --- linux.orig/arch/x86/vdso/vclock_gettime.c
> +++ linux/arch/x86/vdso/vclock_gettime.c

Yes, but both those files now have:

/*
* likely and unlikely explode when used in vdso in combination with
* profile-likely-unlikely-macros.patch
*/
#undef likely
#define likely(x) (x)
#undef unlikely
#define unlikely(x) (x)

at the top, so it'll be something else. Perhaps a `likely' snuck in via an
inline in a header file. It would be better to add a #define DONT_DO_THAT
at the top of arch/x86/kernel/vsyscall_64.c and
arch/x86/vdso/vclock_gettime.c, then use that to defeat likely-profiling.

arch/x86/kernel/vsyscall_64.c | 11 ++---------
arch/x86/vdso/vclock_gettime.c | 11 ++---------
include/linux/compiler.h | 3 ++-
3 files changed, 6 insertions(+), 19 deletions(-)

diff -puN arch/x86/kernel/vsyscall_64.c~profile-likely-unlikely-macros-fix arch/x86/kernel/vsyscall_64.c
--- a/arch/x86/kernel/vsyscall_64.c~profile-likely-unlikely-macros-fix
+++ a/arch/x86/kernel/vsyscall_64.c
@@ -17,6 +17,8 @@
* want per guest time just set the kernel.vsyscall64 sysctl to 0.
*/

+#define SUPPRESS_LIKELY_PROFILING
+
#include <linux/time.h>
#include <linux/init.h>
#include <linux/kernel.h>
@@ -46,15 +48,6 @@
#define __syscall_clobber "r11","cx","memory"

/*
- * likely and unlikely explode when used in vdso in combination with
- * profile-likely-unlikely-macros.patch
- */
-#undef likely
-#define likely(x) (x)
-#undef unlikely
-#define unlikely(x) (x)
-
-/*
* vsyscall_gtod_data contains data that is :
* - readonly from vsyscalls
* - written by timer interrupt or systcl (/proc/sys/kernel/vsyscall64)
diff -puN arch/x86/vdso/vclock_gettime.c~profile-likely-unlikely-macros-fix arch/x86/vdso/vclock_gettime.c
--- a/arch/x86/vdso/vclock_gettime.c~profile-likely-unlikely-macros-fix
+++ a/arch/x86/vdso/vclock_gettime.c
@@ -9,6 +9,8 @@
* Also alternative() doesn't work.
*/

+#define SUPPRESS_LIKELY_PROFILING
+
#include <linux/kernel.h>
#include <linux/posix-timers.h>
#include <linux/time.h>
@@ -23,15 +25,6 @@

#define gtod vdso_vsyscall_gtod_data

-/*
- * likely and unlikely explode when used in vdso in combination with
- * profile-likely-unlikely-macros.patch
- */
-#undef likely
-#define likely(x) (x)
-#undef unlikely
-#define unlikely(x) (x)
-
static long vdso_fallback_gettime(long clock, struct timespec *ts)
{
long ret;
diff -puN include/linux/compiler.h~profile-likely-unlikely-macros-fix include/linux/compiler.h
--- a/include/linux/compiler.h~profile-likely-unlikely-macros-fix
+++ a/include/linux/compiler.h
@@ -51,7 +51,8 @@ extern void __chk_io_ptr(const volatile
# include <linux/compiler-intel.h>
#endif

-#if defined(CONFIG_PROFILE_LIKELY) && !(defined(CONFIG_MODULE_UNLOAD) && defined(MODULE))
+#if defined(CONFIG_PROFILE_LIKELY) && !defined(SUPPRESS_LIKELY_PROFILING) && \
+ !(defined(CONFIG_MODULE_UNLOAD) && defined(MODULE))
struct likeliness {
const char *func;
char *file;
_


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