[PATCH 3/3] riscv: add PREEMPT_LAZY support

[PATCH 3/3] riscv: add PREEMPT_LAZY support

[Sebastian Andrzej Siewior]

From: Jisheng Zhang <jszhang@kernel.org>

riscv has switched to GENERIC_ENTRY, so adding PREEMPT_LAZY is as simple
as adding TIF_NEED_RESCHED_LAZY related definitions and enabling
ARCH_HAS_PREEMPT_LAZY.

[bigeasy: Replace old PREEMPT_AUTO bits with new PREEMPT_LAZY ]

Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: linux-riscv@lists.infradead.org
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/riscv/Kconfig                   | 1 +
 arch/riscv/include/asm/thread_info.h | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 62545946ecf43..3516c58480612 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -39,6 +39,7 @@ config RISCV
 	select ARCH_HAS_MMIOWB
 	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
 	select ARCH_HAS_PMEM_API
+	select ARCH_HAS_PREEMPT_LAZY
 	select ARCH_HAS_PREPARE_SYNC_CORE_CMD
 	select ARCH_HAS_PTE_DEVMAP if 64BIT && MMU
 	select ARCH_HAS_PTE_SPECIAL
diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
index 9c10fb180f438..8b5a5ddea4293 100644
--- a/arch/riscv/include/asm/thread_info.h
+++ b/arch/riscv/include/asm/thread_info.h
@@ -107,6 +107,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
  * - pending work-to-be-done flags are in lowest half-word
  * - other flags in upper half-word(s)
  */
+#define TIF_NEED_RESCHED_LAZY	0       /* Lazy rescheduling needed */
 #define TIF_NOTIFY_RESUME	1	/* callback before returning to user */
 #define TIF_SIGPENDING		2	/* signal pending */
 #define TIF_NEED_RESCHED	3	/* rescheduling necessary */
@@ -117,6 +118,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
 #define TIF_32BIT		11	/* compat-mode 32bit process */
 #define TIF_RISCV_V_DEFER_RESTORE	12 /* restore Vector before returing to user */
 
+#define _TIF_NEED_RESCHED_LAZY	(1 << TIF_NEED_RESCHED_LAZY)
 #define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)
 #define _TIF_SIGPENDING		(1 << TIF_SIGPENDING)
 #define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)
-- 
2.45.2


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Re: [PATCH 3/3] riscv: add PREEMPT_LAZY support

[Peter Zijlstra]

On Wed, Oct 09, 2024 at 12:50:57PM +0200, Sebastian Andrzej Siewior wrote:
> From: Jisheng Zhang <jszhang@kernel.org>
> 
> riscv has switched to GENERIC_ENTRY, so adding PREEMPT_LAZY is as simple
> as adding TIF_NEED_RESCHED_LAZY related definitions and enabling
> ARCH_HAS_PREEMPT_LAZY.
> 
> [bigeasy: Replace old PREEMPT_AUTO bits with new PREEMPT_LAZY ]
> 
> Cc: Paul Walmsley <paul.walmsley@sifive.com>
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> Cc: Albert Ou <aou@eecs.berkeley.edu>
> Cc: linux-riscv@lists.infradead.org
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  arch/riscv/Kconfig                   | 1 +
>  arch/riscv/include/asm/thread_info.h | 2 ++
>  2 files changed, 3 insertions(+)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 62545946ecf43..3516c58480612 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -39,6 +39,7 @@ config RISCV
>  	select ARCH_HAS_MMIOWB
>  	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
>  	select ARCH_HAS_PMEM_API
> +	select ARCH_HAS_PREEMPT_LAZY
>  	select ARCH_HAS_PREPARE_SYNC_CORE_CMD
>  	select ARCH_HAS_PTE_DEVMAP if 64BIT && MMU
>  	select ARCH_HAS_PTE_SPECIAL
> diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
> index 9c10fb180f438..8b5a5ddea4293 100644
> --- a/arch/riscv/include/asm/thread_info.h
> +++ b/arch/riscv/include/asm/thread_info.h
> @@ -107,6 +107,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
>   * - pending work-to-be-done flags are in lowest half-word
>   * - other flags in upper half-word(s)
>   */
> +#define TIF_NEED_RESCHED_LAZY	0       /* Lazy rescheduling needed */
>  #define TIF_NOTIFY_RESUME	1	/* callback before returning to user */
>  #define TIF_SIGPENDING		2	/* signal pending */
>  #define TIF_NEED_RESCHED	3	/* rescheduling necessary */

So for x86 I shuffled the flags around to have the two NEED_RESCHED ones
side-by-side. Not strictly required ofcourse, but...

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Re: [PATCH 3/3] riscv: add PREEMPT_LAZY support

[Sebastian Andrzej Siewior]

On 2024-10-09 15:03:07 [+0200], Peter Zijlstra wrote:
> > diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
> > index 9c10fb180f438..8b5a5ddea4293 100644
> > --- a/arch/riscv/include/asm/thread_info.h
> > +++ b/arch/riscv/include/asm/thread_info.h
> > @@ -107,6 +107,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
> >   * - pending work-to-be-done flags are in lowest half-word
> >   * - other flags in upper half-word(s)
> >   */
> > +#define TIF_NEED_RESCHED_LAZY	0       /* Lazy rescheduling needed */
> >  #define TIF_NOTIFY_RESUME	1	/* callback before returning to user */
> >  #define TIF_SIGPENDING		2	/* signal pending */
> >  #define TIF_NEED_RESCHED	3	/* rescheduling necessary */
> 
> So for x86 I shuffled the flags around to have the two NEED_RESCHED ones
> side-by-side. Not strictly required ofcourse, but...

I can shuffle them. I don't think the riscv camp will complain (saying
this for them to actual complain if so).

Sebastian

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[PATCH v2 3/3] riscv: add PREEMPT_LAZY support

[Sebastian Andrzej Siewior]

From: Jisheng Zhang <jszhang@kernel.org>

riscv has switched to GENERIC_ENTRY, so adding PREEMPT_LAZY is as simple
as adding TIF_NEED_RESCHED_LAZY related definitions and enabling
ARCH_HAS_PREEMPT_LAZY.

[bigeasy: Replace old PREEMPT_AUTO bits with new PREEMPT_LAZY ]

Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: linux-riscv@lists.infradead.org
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---

v1…v2:
  - shuffle TIF bits around to make RESCHED next to RESCHED_LAZY.
    Compiles & boots.

 arch/riscv/Kconfig                   |  1 +
 arch/riscv/include/asm/thread_info.h | 10 ++++++----
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 62545946ecf43..3516c58480612 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -39,6 +39,7 @@ config RISCV
 	select ARCH_HAS_MMIOWB
 	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
 	select ARCH_HAS_PMEM_API
+	select ARCH_HAS_PREEMPT_LAZY
 	select ARCH_HAS_PREPARE_SYNC_CORE_CMD
 	select ARCH_HAS_PTE_DEVMAP if 64BIT && MMU
 	select ARCH_HAS_PTE_SPECIAL
diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
index 9c10fb180f438..f5916a70879a8 100644
--- a/arch/riscv/include/asm/thread_info.h
+++ b/arch/riscv/include/asm/thread_info.h
@@ -107,9 +107,10 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
  * - pending work-to-be-done flags are in lowest half-word
  * - other flags in upper half-word(s)
  */
-#define TIF_NOTIFY_RESUME	1	/* callback before returning to user */
-#define TIF_SIGPENDING		2	/* signal pending */
-#define TIF_NEED_RESCHED	3	/* rescheduling necessary */
+#define TIF_NEED_RESCHED	0	/* rescheduling necessary */
+#define TIF_NEED_RESCHED_LAZY	1       /* Lazy rescheduling needed */
+#define TIF_NOTIFY_RESUME	2	/* callback before returning to user */
+#define TIF_SIGPENDING		3	/* signal pending */
 #define TIF_RESTORE_SIGMASK	4	/* restore signal mask in do_signal() */
 #define TIF_MEMDIE		5	/* is terminating due to OOM killer */
 #define TIF_NOTIFY_SIGNAL	9	/* signal notifications exist */
@@ -117,9 +118,10 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
 #define TIF_32BIT		11	/* compat-mode 32bit process */
 #define TIF_RISCV_V_DEFER_RESTORE	12 /* restore Vector before returing to user */
 
+#define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)
+#define _TIF_NEED_RESCHED_LAZY	(1 << TIF_NEED_RESCHED_LAZY)
 #define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)
 #define _TIF_SIGPENDING		(1 << TIF_SIGPENDING)
-#define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)
 #define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
 #define _TIF_UPROBE		(1 << TIF_UPROBE)
 #define _TIF_RISCV_V_DEFER_RESTORE	(1 << TIF_RISCV_V_DEFER_RESTORE)
-- 
2.45.2


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Re: [PATCH 3/3] riscv: add PREEMPT_LAZY support

[Palmer Dabbelt]

On Wed, 09 Oct 2024 06:05:30 PDT (-0700), bigeasy@linutronix.de wrote:
> On 2024-10-09 15:03:07 [+0200], Peter Zijlstra wrote:
>> > diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
>> > index 9c10fb180f438..8b5a5ddea4293 100644
>> > --- a/arch/riscv/include/asm/thread_info.h
>> > +++ b/arch/riscv/include/asm/thread_info.h
>> > @@ -107,6 +107,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
>> >   * - pending work-to-be-done flags are in lowest half-word
>> >   * - other flags in upper half-word(s)
>> >   */
>> > +#define TIF_NEED_RESCHED_LAZY	0       /* Lazy rescheduling needed */
>> >  #define TIF_NOTIFY_RESUME	1	/* callback before returning to user */
>> >  #define TIF_SIGPENDING		2	/* signal pending */
>> >  #define TIF_NEED_RESCHED	3	/* rescheduling necessary */
>>
>> So for x86 I shuffled the flags around to have the two NEED_RESCHED ones
>> side-by-side. Not strictly required ofcourse, but...
>
> I can shuffle them. I don't think the riscv camp will complain (saying
> this for them to actual complain if so).

Acked-by: Palmer Dabbelt <palmer@rivosinc.com>

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Re: [PATCH v2 3/3] riscv: add PREEMPT_LAZY support

[patchwork-bot+linux-riscv]

Hello:

This patch was applied to riscv/linux.git (fixes)
by Peter Zijlstra <peterz@infradead.org>:

On Thu, 10 Oct 2024 14:25:45 +0200 you wrote:
> From: Jisheng Zhang <jszhang@kernel.org>
> 
> riscv has switched to GENERIC_ENTRY, so adding PREEMPT_LAZY is as simple
> as adding TIF_NEED_RESCHED_LAZY related definitions and enabling
> ARCH_HAS_PREEMPT_LAZY.
> 
> [bigeasy: Replace old PREEMPT_AUTO bits with new PREEMPT_LAZY ]
> 
> [...]

Here is the summary with links:
  - [v2,3/3] riscv: add PREEMPT_LAZY support
    https://git.kernel.org/riscv/c/22aaec357c1f

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html



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