[patch] preempt: select PREEMPT_DYNAMIC under PREEMPTION instead of PREEMPT

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* [patch] preempt: select PREEMPT_DYNAMIC under PREEMPTION instead of PREEMPT
@ 2021-02-09 13:45 Mike Galbraith
  2021-02-09 15:13 ` Peter Zijlstra
  0 siblings, 1 reply; 11+ messages in thread
From: Mike Galbraith @ 2021-02-09 13:45 UTC (permalink / raw)
  To: lkml; +Cc: Peter Zijlstra, Michal Hocko


PREEMPT_RT and PREEMPT both needs PREEMPT_DYNAMIC to build, so move
selection of PREEMPT_DYNAMIC to the common denominator, PREEMPTION.

Signed-off-by: Mike Galbraith <efault@gmx.de>
---
 kernel/Kconfig.preempt |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -40,7 +40,6 @@ config PREEMPT
 	depends on !ARCH_NO_PREEMPT
 	select PREEMPTION
 	select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
-	select PREEMPT_DYNAMIC if HAVE_PREEMPT_DYNAMIC
 	help
 	  This option reduces the latency of the kernel by making
 	  all kernel code (that is not executing in a critical section)
@@ -81,6 +80,7 @@ config PREEMPT_COUNT
 config PREEMPTION
        bool
        select PREEMPT_COUNT
+       select PREEMPT_DYNAMIC if HAVE_PREEMPT_DYNAMIC

 config PREEMPT_DYNAMIC
 	bool


^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [patch] preempt: select PREEMPT_DYNAMIC under PREEMPTION instead of PREEMPT
  2021-02-09 13:45 [patch] preempt: select PREEMPT_DYNAMIC under PREEMPTION instead of PREEMPT Mike Galbraith
@ 2021-02-09 15:13 ` Peter Zijlstra
  2021-02-09 16:05   ` Mike Galbraith
  0 siblings, 1 reply; 11+ messages in thread
From: Peter Zijlstra @ 2021-02-09 15:13 UTC (permalink / raw)
  To: Mike Galbraith; +Cc: lkml, Michal Hocko, Thomas Gleixner

On Tue, Feb 09, 2021 at 02:45:37PM +0100, Mike Galbraith wrote:
> 
> PREEMPT_RT and PREEMPT both needs PREEMPT_DYNAMIC to build, so move
> selection of PREEMPT_DYNAMIC to the common denominator, PREEMPTION.

I'm confused, why would you want PREEMPT_DYNAMIC for PREEMPT_RT ?

PREEMPT_RT without full preemption is just plain daft, no?

^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [patch] preempt: select PREEMPT_DYNAMIC under PREEMPTION instead of PREEMPT
  2021-02-09 15:13 ` Peter Zijlstra
@ 2021-02-09 16:05   ` Mike Galbraith
  2021-02-09 16:13     ` Peter Zijlstra
  0 siblings, 1 reply; 11+ messages in thread
From: Mike Galbraith @ 2021-02-09 16:05 UTC (permalink / raw)
  To: Peter Zijlstra; +Cc: lkml, Michal Hocko, Thomas Gleixner

On Tue, 2021-02-09 at 16:13 +0100, Peter Zijlstra wrote:
> On Tue, Feb 09, 2021 at 02:45:37PM +0100, Mike Galbraith wrote:
> >
> > PREEMPT_RT and PREEMPT both needs PREEMPT_DYNAMIC to build, so move
> > selection of PREEMPT_DYNAMIC to the common denominator, PREEMPTION.
>
> I'm confused, why would you want PREEMPT_DYNAMIC for
> PREEMPT_RT ?
>
> PREEMPT_RT without full preemption is just plain daft, no?

If you turn on PREEMPT, PREEMPT_DYNAMIC is selected because
HAVE_PREEMPT_DYNAMIC is true.

homer:..kernel/linux-tip # grep PREEMPT .config
# CONFIG_PREEMPT_NONE is not set
# CONFIG_PREEMPT_VOLUNTARY is not set
CONFIG_PREEMPT=y
CONFIG_PREEMPT_COUNT=y
CONFIG_PREEMPTION=y
CONFIG_PREEMPT_DYNAMIC=y
CONFIG_PREEMPT_RCU=y
CONFIG_HAVE_PREEMPT_DYNAMIC=y
CONFIG_PREEMPT_NOTIFIERS=y
CONFIG_DRM_I915_PREEMPT_TIMEOUT=640
CONFIG_DEBUG_PREEMPT=y
# CONFIG_PREEMPT_TRACER is not set
# CONFIG_PREEMPTIRQ_DELAY_TEST is not set

Now over to tip-rt, with patchlet...

homer:..kernel/linux-tip-rt # grep PREEMPT .config
CONFIG_HAVE_PREEMPT_LAZY=y
CONFIG_PREEMPT_LAZY=y
# CONFIG_PREEMPT_NONE is not set
# CONFIG_PREEMPT_VOLUNTARY is not set
# CONFIG_PREEMPT is not set
CONFIG_PREEMPT_RT=y
CONFIG_PREEMPT_COUNT=y
CONFIG_PREEMPTION=y
CONFIG_PREEMPT_DYNAMIC=y
CONFIG_PREEMPT_RCU=y
CONFIG_HAVE_PREEMPT_DYNAMIC=y
CONFIG_PREEMPT_NOTIFIERS=y
CONFIG_DRM_I915_PREEMPT_TIMEOUT=640
CONFIG_DEBUG_PREEMPT=y
# CONFIG_PREEMPT_TRACER is not set
# CONFIG_PREEMPTIRQ_DELAY_TEST is not set

...tree builds/runs.  Pop patchlet, and...

  LD      vmlinux.o
  MODPOST vmlinux.symvers
  MODINFO modules.builtin.modinfo
  GEN     modules.builtin
  LD      .tmp_vmlinux.kallsyms1
ld: init/main.o: in function `trace_initcall_start':
/backup/usr/local/src/kernel/linux-tip-rt/./include/trace/events/initcall.h:27: undefined reference to `__SCT__preempt_schedule_notrace'
ld: init/main.o: in function `trace_initcall_finish':
/backup/usr/local/src/kernel/linux-tip-rt/./include/trace/events/initcall.h:48: undefined reference to `__SCT__preempt_schedule_notrace'
ld: init/main.o: in function `trace_initcall_level':
/backup/usr/local/src/kernel/linux-tip-rt/./include/trace/events/initcall.h:10: undefined reference to `__SCT__preempt_schedule_notrace'
ld: init/main.o:(.static_call_sites+0x4): undefined reference to `__SCK__preempt_schedule_notrace'
ld: init/main.o:(.static_call_sites+0x14): undefined reference to `__SCK__preempt_schedule_notrace'
ld: init/main.o:(.static_call_sites+0x24): undefined reference to `__SCK__preempt_schedule_notrace'
ld: arch/x86/entry/vsyscall/vsyscall_64.o: in function `trace_emulate_vsyscall':
/backup/usr/local/src/kernel/linux-tip-rt/arch/x86/entry/vsyscall/vsyscall_trace.h:10: undefined reference to `__SCT__preempt_schedule_notrace'
ld: arch/x86/entry/vsyscall/vsyscall_64.o:(.static_call_sites+0x4): undefined reference to `__SCK__preempt_schedule_notrace'
ld: arch/x86/events/amd/ibs.o: in function `ibs_eilvt_valid':
/backup/usr/local/src/kernel/linux-tip-rt/arch/x86/events/amd/ibs.c:865: undefined reference to `__SCT__preempt_schedule'
ld: arch/x86/events/amd/ibs.o: in function `force_ibs_eilvt_setup':
/backup/usr/local/src/kernel/linux-tip-rt/arch/x86/events/amd/ibs.c:923: undefined reference to `__SCT__preempt_schedule'
ld: /backup/usr/local/src/kernel/linux-tip-rt/arch/x86/events/amd/ibs.c:943: undefined reference to `__SCT__preempt_schedule'
ld: arch/x86/events/amd/ibs.o: in function `ibs_eilvt_valid':
/backup/usr/local/src/kernel/linux-tip-rt/arch/x86/events/amd/ibs.c:865: undefined reference to `__SCT__preempt_schedule'
...

^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [patch] preempt: select PREEMPT_DYNAMIC under PREEMPTION instead of PREEMPT
  2021-02-09 16:05   ` Mike Galbraith
@ 2021-02-09 16:13     ` Peter Zijlstra
  2021-02-09 16:19       ` Peter Zijlstra
  2021-02-09 16:27       ` [patch] preempt: select PREEMPT_DYNAMIC under PREEMPTION instead of PREEMPT Mike Galbraith
  0 siblings, 2 replies; 11+ messages in thread
From: Peter Zijlstra @ 2021-02-09 16:13 UTC (permalink / raw)
  To: Mike Galbraith; +Cc: lkml, Michal Hocko, Thomas Gleixner

On Tue, Feb 09, 2021 at 05:05:14PM +0100, Mike Galbraith wrote:

> ld: init/main.o: in function `trace_initcall_start':
> /backup/usr/local/src/kernel/linux-tip-rt/./include/trace/events/initcall.h:27: undefined reference to `__SCT__preempt_schedule_notrace'

Ooohh... this is because x86 can't build PREEMPT without PREEMPT_DYNAMIC
anymore. Maybe I should fix that. Lemme see what that would take.



^ permalink raw reply	[flat|nested] 11+ messages in thread

* Re: [patch] preempt: select PREEMPT_DYNAMIC under PREEMPTION instead of PREEMPT
  2021-02-09 16:13     ` Peter Zijlstra
@ 2021-02-09 16:19       ` Peter Zijlstra
  2021-02-09 16:46         ` Mike Galbraith
                           ` (2 more replies)
  2021-02-09 16:27       ` [patch] preempt: select PREEMPT_DYNAMIC under PREEMPTION instead of PREEMPT Mike Galbraith
  1 sibling, 3 replies; 11+ messages in thread
From: Peter Zijlstra @ 2021-02-09 16:19 UTC (permalink / raw)
  To: Mike Galbraith; +Cc: lkml, Michal Hocko, Thomas Gleixner

On Tue, Feb 09, 2021 at 05:13:15PM +0100, Peter Zijlstra wrote:
> On Tue, Feb 09, 2021 at 05:05:14PM +0100, Mike Galbraith wrote:
> 
> > ld: init/main.o: in function `trace_initcall_start':
> > /backup/usr/local/src/kernel/linux-tip-rt/./include/trace/events/initcall.h:27: undefined reference to `__SCT__preempt_schedule_notrace'
> 
> Ooohh... this is because x86 can't build PREEMPT without PREEMPT_DYNAMIC
> anymore. Maybe I should fix that. Lemme see what that would take.

Does this work?

---
diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index 0aa96f824af1..f8cb8af4de5c 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -110,6 +110,13 @@ extern asmlinkage void preempt_schedule_thunk(void);
 
 #define __preempt_schedule_func preempt_schedule_thunk
 
+extern asmlinkage void preempt_schedule_notrace(void);
+extern asmlinkage void preempt_schedule_notrace_thunk(void);
+
+#define __preempt_schedule_notrace_func preempt_schedule_notrace_thunk
+
+#ifdef CONFIG_PREEMPT_DYNAMIC
+
 DECLARE_STATIC_CALL(preempt_schedule, __preempt_schedule_func);
 
 #define __preempt_schedule() \
@@ -118,11 +125,6 @@ do { \
 	asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule) : ASM_CALL_CONSTRAINT); \
 } while (0)
 
-extern asmlinkage void preempt_schedule_notrace(void);
-extern asmlinkage void preempt_schedule_notrace_thunk(void);
-
-#define __preempt_schedule_notrace_func preempt_schedule_notrace_thunk
-
 DECLARE_STATIC_CALL(preempt_schedule_notrace, __preempt_schedule_notrace_func);
 
 #define __preempt_schedule_notrace() \
@@ -131,6 +133,16 @@ do { \
 	asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule_notrace) : ASM_CALL_CONSTRAINT); \
 } while (0)
 
-#endif
+#else /* PREEMPT_DYNAMIC */
+
+#define __preempt_schedule() \
+	asm volatile ("call preempt_schedule_thunk" : ASM_CALL_CONSTRAINT);
+
+#define __preempt_schedule_notrace() \
+	asm volatile ("call preempt_schedule_notrace_thunk" : ASM_CALL_CONSTRAINT);
+
+#endif /* PREEMPT_DYNAMIC */
+
+#endif /* PREEMPTION */
 
 #endif /* __ASM_PREEMPT_H */

^ permalink raw reply related	[flat|nested] 11+ messages in thread

* Re: [patch] preempt: select PREEMPT_DYNAMIC under PREEMPTION instead of PREEMPT
  2021-02-09 16:19       ` Peter Zijlstra
@ 2021-02-09 16:46         ` Mike Galbraith
  2021-02-10 13:53         ` [tip: sched/core] sched,x86: Allow !PREEMPT_DYNAMIC tip-bot2 for Peter Zijlstra
  2021-02-17 13:17         ` tip-bot2 for Peter Zijlstra
  2 siblings, 0 replies; 11+ messages in thread
From: Mike Galbraith @ 2021-02-09 16:46 UTC (permalink / raw)
  To: Peter Zijlstra; +Cc: lkml, Michal Hocko, Thomas Gleixner

On Tue, 2021-02-09 at 17:19 +0100, Peter Zijlstra wrote:
> On Tue, Feb 09, 2021 at 05:13:15PM +0100, Peter Zijlstra wrote:
> > On Tue, Feb 09, 2021 at 05:05:14PM +0100, Mike Galbraith wrote:
> >
> > > ld: init/main.o: in function `trace_initcall_start':
> > > /backup/usr/local/src/kernel/linux-tip-rt/./include/trace/events/initcall.h:27: undefined reference to `__SCT__preempt_schedule_notrace'
> >
> > Ooohh... this is because x86 can't build PREEMPT without PREEMPT_DYNAMIC
> > anymore. Maybe I should fix that. Lemme see what that would take.
>
> Does this work?

Yup, worked fine.

	-Mike


^ permalink raw reply	[flat|nested] 11+ messages in thread

* [tip: sched/core] sched,x86: Allow !PREEMPT_DYNAMIC
  2021-02-09 16:19       ` Peter Zijlstra
  2021-02-09 16:46         ` Mike Galbraith
@ 2021-02-10 13:53         ` tip-bot2 for Peter Zijlstra
  2021-02-10 14:18           ` Frederic Weisbecker
  2021-02-17 13:17         ` tip-bot2 for Peter Zijlstra
  2 siblings, 1 reply; 11+ messages in thread
From: tip-bot2 for Peter Zijlstra @ 2021-02-10 13:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Mike Galbraith, Peter Zijlstra (Intel), x86, linux-kernel

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     82891be90f3c42dc964fd61b8b2a89de12940c9f
Gitweb:        https://git.kernel.org/tip/82891be90f3c42dc964fd61b8b2a89de12940c9f
Author:        Peter Zijlstra <peterz@infradead.org>
AuthorDate:    Tue, 09 Feb 2021 22:02:33 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 10 Feb 2021 14:44:51 +01:00

sched,x86: Allow !PREEMPT_DYNAMIC

Allow building x86 with PREEMPT_DYNAMIC=n, this is needed for
PREEMPT_RT as it makes no sense to not have full preemption on
PREEMPT_RT.

Fixes: 8c98e8cf723c ("preempt/dynamic: Provide preempt_schedule[_notrace]() static calls")
Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Mike Galbraith <efault@gmx.de>
Link: https://lkml.kernel.org/r/YCK1+JyFNxQnWeXK@hirez.programming.kicks-ass.net
---
 arch/x86/include/asm/preempt.h | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index 0aa96f8..f8cb8af 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -110,6 +110,13 @@ extern asmlinkage void preempt_schedule_thunk(void);
 
 #define __preempt_schedule_func preempt_schedule_thunk
 
+extern asmlinkage void preempt_schedule_notrace(void);
+extern asmlinkage void preempt_schedule_notrace_thunk(void);
+
+#define __preempt_schedule_notrace_func preempt_schedule_notrace_thunk
+
+#ifdef CONFIG_PREEMPT_DYNAMIC
+
 DECLARE_STATIC_CALL(preempt_schedule, __preempt_schedule_func);
 
 #define __preempt_schedule() \
@@ -118,11 +125,6 @@ do { \
 	asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule) : ASM_CALL_CONSTRAINT); \
 } while (0)
 
-extern asmlinkage void preempt_schedule_notrace(void);
-extern asmlinkage void preempt_schedule_notrace_thunk(void);
-
-#define __preempt_schedule_notrace_func preempt_schedule_notrace_thunk
-
 DECLARE_STATIC_CALL(preempt_schedule_notrace, __preempt_schedule_notrace_func);
 
 #define __preempt_schedule_notrace() \
@@ -131,6 +133,16 @@ do { \
 	asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule_notrace) : ASM_CALL_CONSTRAINT); \
 } while (0)
 
-#endif
+#else /* PREEMPT_DYNAMIC */
+
+#define __preempt_schedule() \
+	asm volatile ("call preempt_schedule_thunk" : ASM_CALL_CONSTRAINT);
+
+#define __preempt_schedule_notrace() \
+	asm volatile ("call preempt_schedule_notrace_thunk" : ASM_CALL_CONSTRAINT);
+
+#endif /* PREEMPT_DYNAMIC */
+
+#endif /* PREEMPTION */
 
 #endif /* __ASM_PREEMPT_H */

^ permalink raw reply related	[flat|nested] 11+ messages in thread

* Re: [tip: sched/core] sched,x86: Allow !PREEMPT_DYNAMIC
  2021-02-10 13:53         ` [tip: sched/core] sched,x86: Allow !PREEMPT_DYNAMIC tip-bot2 for Peter Zijlstra
@ 2021-02-10 14:18           ` Frederic Weisbecker
  2021-02-16 10:38             ` Peter Zijlstra
  0 siblings, 1 reply; 11+ messages in thread
From: Frederic Weisbecker @ 2021-02-10 14:18 UTC (permalink / raw)
  To: linux-kernel
  Cc: linux-tip-commits, Mike Galbraith, Peter Zijlstra (Intel), x86

On Wed, Feb 10, 2021 at 01:53:31PM -0000, tip-bot2 for Peter Zijlstra wrote:
> The following commit has been merged into the sched/core branch of tip:
> 
> Commit-ID:     82891be90f3c42dc964fd61b8b2a89de12940c9f
> Gitweb:        https://git.kernel.org/tip/82891be90f3c42dc964fd61b8b2a89de12940c9f
> Author:        Peter Zijlstra <peterz@infradead.org>
> AuthorDate:    Tue, 09 Feb 2021 22:02:33 +01:00
> Committer:     Peter Zijlstra <peterz@infradead.org>
> CommitterDate: Wed, 10 Feb 2021 14:44:51 +01:00
> 
> sched,x86: Allow !PREEMPT_DYNAMIC
> 
> Allow building x86 with PREEMPT_DYNAMIC=n, this is needed for
> PREEMPT_RT as it makes no sense to not have full preemption on
> PREEMPT_RT.
> 
> Fixes: 8c98e8cf723c ("preempt/dynamic: Provide preempt_schedule[_notrace]() static calls")
> Reported-by: Mike Galbraith <efault@gmx.de>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Tested-by: Mike Galbraith <efault@gmx.de>
> Link: https://lkml.kernel.org/r/YCK1+JyFNxQnWeXK@hirez.programming.kicks-ass.net

Also should we add something like this?

From 4e1de6d9d8804ea7edc6f8767abea37f5103799a Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <frederic@kernel.org>
Date: Wed, 10 Feb 2021 15:11:39 +0100
Subject: [PATCH] preempt/dynamic: Make PREEMPT_DYNAMIC optional

In order not to make the small trampoline overhead mandatory for archs
that support HAVE_STATIC_CALL but not HAVE_STATIC_CALL_INLINE, make
PREEMPT_DYNAMIC optional.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
 kernel/Kconfig.preempt | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
index 416017301660..1fe759677907 100644
--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -40,7 +40,6 @@ config PREEMPT
 	depends on !ARCH_NO_PREEMPT
 	select PREEMPTION
 	select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
-	select PREEMPT_DYNAMIC if HAVE_PREEMPT_DYNAMIC
 	help
 	  This option reduces the latency of the kernel by making
 	  all kernel code (that is not executing in a critical section)
@@ -83,11 +82,13 @@ config PREEMPTION
        select PREEMPT_COUNT
 
 config PREEMPT_DYNAMIC
-	bool
+	bool "Override preemption flavour at boot time"
+	depends on HAVE_PREEMPT_DYNAMIC && PREEMPT
+	default HAVE_STATIC_CALL_INLINE
 	help
 	  This option allows to define the preemption model on the kernel
-	  command line parameter and thus override the default preemption
-	  model defined during compile time.
+	  command line parameter "preempt=" and thus override the default
+	  preemption model defined during compile time.
 
 	  The feature is primarily interesting for Linux distributions which
 	  provide a pre-built kernel binary to reduce the number of kernel
@@ -99,3 +100,5 @@ config PREEMPT_DYNAMIC
 
 	  Interesting if you want the same pre-built kernel should be used for
 	  both Server and Desktop workloads.
+
+	  Say Y if you have CONFIG_HAVE_STATIC_CALL_INLINE.
-- 
2.25.1


^ permalink raw reply related	[flat|nested] 11+ messages in thread

* Re: [tip: sched/core] sched,x86: Allow !PREEMPT_DYNAMIC
  2021-02-10 14:18           ` Frederic Weisbecker
@ 2021-02-16 10:38             ` Peter Zijlstra
  0 siblings, 0 replies; 11+ messages in thread
From: Peter Zijlstra @ 2021-02-16 10:38 UTC (permalink / raw)
  To: Frederic Weisbecker; +Cc: linux-kernel, linux-tip-commits, Mike Galbraith, x86

On Wed, Feb 10, 2021 at 03:18:38PM +0100, Frederic Weisbecker wrote:
> Also should we add something like this?

I suppose we can do that, but I'd rather have actual numbers to go with
it, I don't think the trampolines are really that terrible.

> From: Frederic Weisbecker <frederic@kernel.org>
> Date: Wed, 10 Feb 2021 15:11:39 +0100
> Subject: [PATCH] preempt/dynamic: Make PREEMPT_DYNAMIC optional
> 
> In order not to make the small trampoline overhead mandatory for archs
> that support HAVE_STATIC_CALL but not HAVE_STATIC_CALL_INLINE, make
> PREEMPT_DYNAMIC optional.
> 
> Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
> ---
>  kernel/Kconfig.preempt | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
> index 416017301660..1fe759677907 100644
> --- a/kernel/Kconfig.preempt
> +++ b/kernel/Kconfig.preempt
> @@ -40,7 +40,6 @@ config PREEMPT
>  	depends on !ARCH_NO_PREEMPT
>  	select PREEMPTION
>  	select UNINLINE_SPIN_UNLOCK if !ARCH_INLINE_SPIN_UNLOCK
> -	select PREEMPT_DYNAMIC if HAVE_PREEMPT_DYNAMIC
>  	help
>  	  This option reduces the latency of the kernel by making
>  	  all kernel code (that is not executing in a critical section)
> @@ -83,11 +82,13 @@ config PREEMPTION
>         select PREEMPT_COUNT
>  
>  config PREEMPT_DYNAMIC
> -	bool
> +	bool "Override preemption flavour at boot time"
> +	depends on HAVE_PREEMPT_DYNAMIC && PREEMPT
> +	default HAVE_STATIC_CALL_INLINE
>  	help
>  	  This option allows to define the preemption model on the kernel
> -	  command line parameter and thus override the default preemption
> -	  model defined during compile time.
> +	  command line parameter "preempt=" and thus override the default
> +	  preemption model defined during compile time.
>  
>  	  The feature is primarily interesting for Linux distributions which
>  	  provide a pre-built kernel binary to reduce the number of kernel
> @@ -99,3 +100,5 @@ config PREEMPT_DYNAMIC
>  
>  	  Interesting if you want the same pre-built kernel should be used for
>  	  both Server and Desktop workloads.
> +
> +	  Say Y if you have CONFIG_HAVE_STATIC_CALL_INLINE.
> -- 
> 2.25.1
> 

^ permalink raw reply	[flat|nested] 11+ messages in thread

* [tip: sched/core] sched,x86: Allow !PREEMPT_DYNAMIC
  2021-02-09 16:19       ` Peter Zijlstra
  2021-02-09 16:46         ` Mike Galbraith
  2021-02-10 13:53         ` [tip: sched/core] sched,x86: Allow !PREEMPT_DYNAMIC tip-bot2 for Peter Zijlstra
@ 2021-02-17 13:17         ` tip-bot2 for Peter Zijlstra
  2 siblings, 0 replies; 11+ messages in thread
From: tip-bot2 for Peter Zijlstra @ 2021-02-17 13:17 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Mike Galbraith, Peter Zijlstra (Intel), Ingo Molnar, x86,
	linux-kernel

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     c5e6fc08feb2b88dc5dac2f3c817e1c2a4cafda4
Gitweb:        https://git.kernel.org/tip/c5e6fc08feb2b88dc5dac2f3c817e1c2a4cafda4
Author:        Peter Zijlstra <peterz@infradead.org>
AuthorDate:    Tue, 09 Feb 2021 22:02:33 +01:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 17 Feb 2021 14:12:43 +01:00

sched,x86: Allow !PREEMPT_DYNAMIC

Allow building x86 with PREEMPT_DYNAMIC=n, this is needed for
PREEMPT_RT as it makes no sense to not have full preemption on
PREEMPT_RT.

Fixes: 8c98e8cf723c ("preempt/dynamic: Provide preempt_schedule[_notrace]() static calls")
Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Mike Galbraith <efault@gmx.de>
Link: https://lkml.kernel.org/r/YCK1+JyFNxQnWeXK@hirez.programming.kicks-ass.net
---
 arch/x86/include/asm/preempt.h | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index 0aa96f8..f8cb8af 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -110,6 +110,13 @@ extern asmlinkage void preempt_schedule_thunk(void);
 
 #define __preempt_schedule_func preempt_schedule_thunk
 
+extern asmlinkage void preempt_schedule_notrace(void);
+extern asmlinkage void preempt_schedule_notrace_thunk(void);
+
+#define __preempt_schedule_notrace_func preempt_schedule_notrace_thunk
+
+#ifdef CONFIG_PREEMPT_DYNAMIC
+
 DECLARE_STATIC_CALL(preempt_schedule, __preempt_schedule_func);
 
 #define __preempt_schedule() \
@@ -118,11 +125,6 @@ do { \
 	asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule) : ASM_CALL_CONSTRAINT); \
 } while (0)
 
-extern asmlinkage void preempt_schedule_notrace(void);
-extern asmlinkage void preempt_schedule_notrace_thunk(void);
-
-#define __preempt_schedule_notrace_func preempt_schedule_notrace_thunk
-
 DECLARE_STATIC_CALL(preempt_schedule_notrace, __preempt_schedule_notrace_func);
 
 #define __preempt_schedule_notrace() \
@@ -131,6 +133,16 @@ do { \
 	asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule_notrace) : ASM_CALL_CONSTRAINT); \
 } while (0)
 
-#endif
+#else /* PREEMPT_DYNAMIC */
+
+#define __preempt_schedule() \
+	asm volatile ("call preempt_schedule_thunk" : ASM_CALL_CONSTRAINT);
+
+#define __preempt_schedule_notrace() \
+	asm volatile ("call preempt_schedule_notrace_thunk" : ASM_CALL_CONSTRAINT);
+
+#endif /* PREEMPT_DYNAMIC */
+
+#endif /* PREEMPTION */
 
 #endif /* __ASM_PREEMPT_H */

^ permalink raw reply related	[flat|nested] 11+ messages in thread

* Re: [patch] preempt: select PREEMPT_DYNAMIC under PREEMPTION instead of PREEMPT
  2021-02-09 16:13     ` Peter Zijlstra
  2021-02-09 16:19       ` Peter Zijlstra
@ 2021-02-09 16:27       ` Mike Galbraith
  1 sibling, 0 replies; 11+ messages in thread
From: Mike Galbraith @ 2021-02-09 16:27 UTC (permalink / raw)
  To: Peter Zijlstra; +Cc: lkml, Michal Hocko, Thomas Gleixner

On Tue, 2021-02-09 at 17:13 +0100, Peter Zijlstra wrote:
> On Tue, Feb 09, 2021 at 05:05:14PM +0100, Mike Galbraith wrote:
>
> > ld: init/main.o: in function `trace_initcall_start':
> > /backup/usr/local/src/kernel/linux-tip-rt/./include/trace/events/initcall.h:27: undefined reference to `__SCT__preempt_schedule_notrace'
>
> Ooohh... this is because x86 can't build PREEMPT without PREEMPT_DYNAMIC
> anymore. Maybe I should fix that. Lemme see what that would take.

Uhoh, looks like something a lot worse managed to sneak into master.
While test-driving that tip-rt build, I couldn't help noticing that
evolution is going mad, chewing cpu and being useless enough that I
couldn't reply to you.  Unfortunately, it ain't my tip-rt tree, nor is
it virgin tip, the evilness is present in virgin master, but not in
5.10 stable.  Hohum, a hunting I shall go I suppose.

	-Mike

^ permalink raw reply	[flat|nested] 11+ messages in thread

end of thread, other threads:[~2021-02-17 13:19 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2021-02-09 13:45 [patch] preempt: select PREEMPT_DYNAMIC under PREEMPTION instead of PREEMPT Mike Galbraith
2021-02-09 15:13 ` Peter Zijlstra
2021-02-09 16:05   ` Mike Galbraith
2021-02-09 16:13     ` Peter Zijlstra
2021-02-09 16:19       ` Peter Zijlstra
2021-02-09 16:46         ` Mike Galbraith
2021-02-10 13:53         ` [tip: sched/core] sched,x86: Allow !PREEMPT_DYNAMIC tip-bot2 for Peter Zijlstra
2021-02-10 14:18           ` Frederic Weisbecker
2021-02-16 10:38             ` Peter Zijlstra
2021-02-17 13:17         ` tip-bot2 for Peter Zijlstra
2021-02-09 16:27       ` [patch] preempt: select PREEMPT_DYNAMIC under PREEMPTION instead of PREEMPT Mike Galbraith

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