ARM: leave it to core code to manage thread_info::cpu

PATCH In review Ard Biesheuvel 2 participants 3 messages Nov 4, 2021 – Nov 15, 2021

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Documentation Arm (32-bit)

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Ard Biesheuvel

author

2021-11-04 08:52 UTC #0 lore raw

PATCH 1/1 ARM: leave it to core code to manage thread_info::cpu

Since commit bcf9033e5449 ("sched: move CPU field back into thread_info if THREAD_INFO_IN_TASK=y"), the CPU field in thread_info went back to being managed by the core code, so we no longer have to keep it in sync in arch code.

While at it, mark THREAD_INFO_IN_TASK as done for ARM in the documentation.

Signed-off-by Ard Biesheuvel <[email protected]>

---
 .../core/thread-info-in-task/arch-support.txt      |  2 +-
 arch/arm/include/asm/switch_to.h                   | 14 --------------
 arch/arm/kernel/smp.c                              |  3 ---
 3 files changed, 1 insertion(+), 18 deletions(-)

Documentation/features/core/thread-info-in-task/arch-support.txt +1 -1

index 3361e86b0958..bc74d8beea72 100644
@@ -8,7 +8,7 @@
     -----------------------
     |       alpha: | TODO |
     |         arc: | TODO |
-    |         arm: | TODO |
+    |         arm: |  ok  |
     |       arm64: |  ok  |
     |        csky: | TODO |
     |       h8300: | TODO |

arch/arm/include/asm/switch_to.h +0 ~~-14~~

index b55c7b2755e4..61e4a3c4ca6e 100644
@@ -23,23 +23,9 @@
  */
 extern struct task_struct *__switch_to(struct task_struct *, struct thread_info *, struct thread_info *);
 
-static inline void set_ti_cpu(struct task_struct *p)
-{
-#ifdef CONFIG_THREAD_INFO_IN_TASK
-	/*
-	 * The core code no longer maintains the thread_info::cpu field once
-	 * CONFIG_THREAD_INFO_IN_TASK is in effect, but we rely on it for
-	 * raw_smp_processor_id(), which cannot access struct task_struct*
-	 * directly for reasons of circular #inclusion hell.
-	 */
-	task_thread_info(p)->cpu = task_cpu(p);
-#endif
-}
-
 #define switch_to(prev,next,last)					\
 do {									\
 	__complete_pending_tlbi();					\
-	set_ti_cpu(next);						\
 	if (IS_ENABLED(CONFIG_CURRENT_POINTER_IN_TPIDRURO))		\
 		__this_cpu_write(__entry_task, next);			\
 	last = __switch_to(prev,task_thread_info(prev), task_thread_info(next));	\

arch/arm/kernel/smp.c +0 -3

index cde5b6d8bac5..97ee6b1567e9 100644
@@ -154,9 +154,6 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 	secondary_data.swapper_pg_dir = get_arch_pgd(swapper_pg_dir);
 #endif
 	secondary_data.task = idle;
-	if (IS_ENABLED(CONFIG_THREAD_INFO_IN_TASK))
-		task_thread_info(idle)->cpu = cpu;
-
 	sync_cache_w(&secondary_data);
 
 	/*

Signature · 7 lines

2.30.2


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Linus Walleij

Reviewed-by on v1 1/1

2021-11-09 11:24 UTC #1 lore raw

Quoted 9 lines · Ard Biesheuvel

Since commit bcf9033e5449 ("sched: move CPU field back into thread_info if THREAD_INFO_IN_TASK=y"), the CPU field in thread_info went back to being managed by the core code, so we no longer have to keep it in sync in arch code.
While at it, mark THREAD_INFO_IN_TASK as done for ARM in the documentation.
Signed-off-by Ard Biesheuvel <[email protected]>

Excellent wrap-up!

Reviewed-by Linus Walleij <[email protected]>

Yours,
Linus Walleij

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Ard Biesheuvel

author

2021-11-15 07:59 UTC #2 lore raw

Quoted 8 lines · Linus Walleij

Quoted 5 lines · Ard Biesheuvel
Since commit bcf9033e5449 ("sched: move CPU field back into thread_info if THREAD_INFO_IN_TASK=y"), the CPU field in thread_info went back to being managed by the core code, so we no longer have to keep it in sync in arch code.

Quoted 8 lines

Quoted 4 lines
While at it, mark THREAD_INFO_IN_TASK as done for ARM in the documentation.
Signed-off-by Ard Biesheuvel <[email protected]>
Excellent wrap-up!
Reviewed-by Linus Walleij <[email protected]>

Submitted as 9158/1

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