Revert "arch: deprecate _current"

Mostly a revert of commit b1def71 ("arch: deprecate `_current`").

This commit was part of PR zephyrproject-rtos#80716 whose initial purpose was about providing
an architecture specific optimization for _current. The actual deprecation
was sneaked in later on without proper discussion.

The Zephyr core always used _current before and that was fine. It is quite
prevalent as well and the alternative is proving rather verbose.
Furthermore, as a concept, the "current thread" is not something that is
necessarily architecture specific. Therefore the primary abstraction
should not carry the arch_ prefix.

Hence this revert.

(cherry picked from commit 46aa671)

Original-Signed-off-by: Nicolas Pitre <[email protected]>
GitOrigin-RevId: 46aa671
Cr-Build-Id: 8726132470642320465
Cr-Build-Url: https://cr-buildbucket.appspot.com/build/8726132470642320465
Copybot-Job-Name: zephyr-main-copybot-downstream
Change-Id: I030e4cdfecfa55c2ec3b1a27b843a8c60484463e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/+/6167306
Reviewed-by: Jonathon Murphy <[email protected]>
Tested-by: Keith Short <[email protected]>
Reviewed-by: Keith Short <[email protected]>
Tested-by: ChromeOS Prod (Robot) <[email protected]>
Commit-Queue: Dawid Niedźwiecki <[email protected]>

Author: Nicolas Pitre

arch/arc/Kconfig

@@ -262,7 +262,7 @@ config ARC_CURRENT_THREAD_USE_NO_TLS
 	  RGF_NUM_BANKS the parameter is disabled by-default because banks syncronization
 	  requires significant time, and it slows down performance.
 	  ARCMWDT works with tls pointer in different way then GCC. Optimized access to
-	  TLS pointer via arch_current_thread() does not provide significant advantages
+	  TLS pointer via the _current symbol does not provide significant advantages
 	  in case of MetaWare.
 
 config GEN_ISR_TABLES

arch/arc/core/fault.c

@@ -55,7 +55,7 @@ static bool z_check_thread_stack_fail(const uint32_t fault_addr, uint32_t sp)
 {
 #if defined(CONFIG_MULTITHREADING)
 	uint32_t guard_end, guard_start;
-	const struct k_thread *thread = arch_current_thread();
+	const struct k_thread *thread = _current;
 
 	if (!thread) {
 		/* TODO: Under what circumstances could we get here ? */

arch/arc/core/irq_offload.c

@@ -49,8 +49,8 @@ void arch_irq_offload(irq_offload_routine_t routine, const void *parameter)
 
 	__asm__ volatile("sync");
 
-	/* If arch_current_thread() was aborted in the offload routine, we shouldn't be here */
-	__ASSERT_NO_MSG((arch_current_thread()->base.thread_state & _THREAD_DEAD) == 0);
+	/* If _current was aborted in the offload routine, we shouldn't be here */
+	__ASSERT_NO_MSG((_current->base.thread_state & _THREAD_DEAD) == 0);
 }
 
 /* need to be executed on every core in the system */

arch/arc/core/thread.c

@@ -210,7 +210,7 @@ void arch_new_thread(struct k_thread *thread, k_thread_stack_t *stack,
 #ifdef CONFIG_MULTITHREADING
 void *z_arch_get_next_switch_handle(struct k_thread **old_thread)
 {
-	*old_thread = arch_current_thread();
+	*old_thread =  _current;
 
 	return z_get_next_switch_handle(NULL);
 }
@@ -227,16 +227,16 @@ void *z_arch_get_next_switch_handle(struct k_thread **old_thread)
 FUNC_NORETURN void arch_user_mode_enter(k_thread_entry_t user_entry,
 					void *p1, void *p2, void *p3)
 {
-	setup_stack_vars(arch_current_thread());
+	setup_stack_vars(_current);
 
 	/* possible optimizaiton: no need to load mem domain anymore */
 	/* need to lock cpu here ? */
-	configure_mpu_thread(arch_current_thread());
+	configure_mpu_thread(_current);
 
 	z_arc_userspace_enter(user_entry, p1, p2, p3,
-			      (uint32_t)arch_current_thread()->stack_info.start,
-			      (arch_current_thread()->stack_info.size -
-			       arch_current_thread()->stack_info.delta), arch_current_thread());
+			      (uint32_t)_current->stack_info.start,
+			      (_current->stack_info.size -
+			       _current->stack_info.delta), _current);
 	CODE_UNREACHABLE;
 }
 #endif
@@ -336,7 +336,7 @@ int arc_vpx_lock(k_timeout_t timeout)
 
 	id = _current_cpu->id;
 #if (CONFIG_MP_MAX_NUM_CPUS > 1) && defined(CONFIG_SCHED_CPU_MASK)
-	__ASSERT(!arch_is_in_isr() && (arch_current_thread()->base.cpu_mask == BIT(id)), "");
+	__ASSERT(!arch_is_in_isr() && (_current->base.cpu_mask == BIT(id)), "");
 #endif
 	k_spin_unlock(&lock, key);
 
@@ -355,7 +355,7 @@ void arc_vpx_unlock(void)
 
 	key = k_spin_lock(&lock);
 #if (CONFIG_MP_MAX_NUM_CPUS > 1) && defined(CONFIG_SCHED_CPU_MASK)
-	__ASSERT(!arch_is_in_isr() && (arch_current_thread()->base.cpu_mask == BIT(id)), "");
+	__ASSERT(!arch_is_in_isr() && (_current->base.cpu_mask == BIT(id)), "");
 #endif
 	id = _current_cpu->id;
 	k_spin_unlock(&lock, key);

arch/arc/core/tls.c

@@ -29,7 +29,7 @@ size_t arch_tls_stack_setup(struct k_thread *new_thread, char *stack_ptr)
 
 void *_Preserve_flags _mwget_tls(void)
 {
-	return (void *)(arch_current_thread()->tls);
+	return (void *)(_current->tls);
 }
 
 #else

arch/arm/core/cortex_a_r/fault.c

@@ -178,7 +178,7 @@ bool z_arm_fault_undef_instruction_fp(void)
 		 * context because it is about to be overwritten.
 		 */
 		if (((_current_cpu->nested == 2)
-				&& (arch_current_thread()->base.user_options & K_FP_REGS))
+				&& (_current->base.user_options & K_FP_REGS))
 			|| ((_current_cpu->nested > 2)
 				&& (spill_esf->undefined & FPEXC_EN))) {
 			/*
@@ -196,7 +196,7 @@ bool z_arm_fault_undef_instruction_fp(void)
 		 * means that a thread that uses the VFP does not have to,
 		 * but should, set K_FP_REGS on thread creation.
 		 */
-		arch_current_thread()->base.user_options |= K_FP_REGS;
+		_current->base.user_options |= K_FP_REGS;
 	}
 
 	return false;

arch/arm/core/cortex_a_r/swap_helper.S

@@ -70,7 +70,7 @@ SECTION_FUNC(TEXT, z_arm_do_swap)
 
 #if defined(CONFIG_FPU_SHARING)
     ldrb r0, [r2, #_thread_offset_to_user_options]
-    tst r0, #K_FP_REGS /* arch_current_thread()->base.user_options & K_FP_REGS */
+    tst r0, #K_FP_REGS /* _current->base.user_options & K_FP_REGS */
     beq out_fp_inactive
 
     mov ip, #FPEXC_EN
@@ -152,7 +152,7 @@ out_fp_inactive:
 
 #if defined(CONFIG_FPU_SHARING)
     ldrb r0, [r2, #_thread_offset_to_user_options]
-    tst r0, #K_FP_REGS /* arch_current_thread()->base.user_options & K_FP_REGS */
+    tst r0, #K_FP_REGS /* _current->base.user_options & K_FP_REGS */
     beq in_fp_inactive
 
     mov r3, #FPEXC_EN

arch/arm/core/cortex_a_r/thread.c

@@ -198,8 +198,8 @@ FUNC_NORETURN void arch_user_mode_enter(k_thread_entry_t user_entry,
 {
 
 	/* Set up privileged stack before entering user mode */
-	arch_current_thread()->arch.priv_stack_start =
-		(uint32_t)z_priv_stack_find(arch_current_thread()->stack_obj);
+	_current->arch.priv_stack_start =
+		(uint32_t)z_priv_stack_find(_current->stack_obj);
 #if defined(CONFIG_MPU_STACK_GUARD)
 #if defined(CONFIG_THREAD_STACK_INFO)
 	/* We're dropping to user mode which means the guard area is no
@@ -208,37 +208,37 @@ FUNC_NORETURN void arch_user_mode_enter(k_thread_entry_t user_entry,
 	 * which accounted for memory borrowed from the thread stack.
 	 */
 #if FP_GUARD_EXTRA_SIZE > 0
-	if ((arch_current_thread()->arch.mode & Z_ARM_MODE_MPU_GUARD_FLOAT_Msk) != 0) {
-		arch_current_thread()->stack_info.start -= FP_GUARD_EXTRA_SIZE;
-		arch_current_thread()->stack_info.size += FP_GUARD_EXTRA_SIZE;
+	if ((_current->arch.mode & Z_ARM_MODE_MPU_GUARD_FLOAT_Msk) != 0) {
+		_current->stack_info.start -= FP_GUARD_EXTRA_SIZE;
+		_current->stack_info.size += FP_GUARD_EXTRA_SIZE;
 	}
 #endif /* FP_GUARD_EXTRA_SIZE */
-	arch_current_thread()->stack_info.start -= MPU_GUARD_ALIGN_AND_SIZE;
-	arch_current_thread()->stack_info.size += MPU_GUARD_ALIGN_AND_SIZE;
+	_current->stack_info.start -= MPU_GUARD_ALIGN_AND_SIZE;
+	_current->stack_info.size += MPU_GUARD_ALIGN_AND_SIZE;
 #endif /* CONFIG_THREAD_STACK_INFO */
 
 	/* Stack guard area reserved at the bottom of the thread's
 	 * privileged stack. Adjust the available (writable) stack
 	 * buffer area accordingly.
 	 */
 #if defined(CONFIG_FPU) && defined(CONFIG_FPU_SHARING)
-	arch_current_thread()->arch.priv_stack_start +=
-		((arch_current_thread()->arch.mode & Z_ARM_MODE_MPU_GUARD_FLOAT_Msk) != 0) ?
+	_current->arch.priv_stack_start +=
+		((_current->arch.mode & Z_ARM_MODE_MPU_GUARD_FLOAT_Msk) != 0) ?
 		MPU_GUARD_ALIGN_AND_SIZE_FLOAT : MPU_GUARD_ALIGN_AND_SIZE;
 #else
-	arch_current_thread()->arch.priv_stack_start += MPU_GUARD_ALIGN_AND_SIZE;
+	_current->arch.priv_stack_start += MPU_GUARD_ALIGN_AND_SIZE;
 #endif /* CONFIG_FPU && CONFIG_FPU_SHARING */
 #endif /* CONFIG_MPU_STACK_GUARD */
 
 #if defined(CONFIG_CPU_AARCH32_CORTEX_R)
-	arch_current_thread()->arch.priv_stack_end =
-		arch_current_thread()->arch.priv_stack_start + CONFIG_PRIVILEGED_STACK_SIZE;
+	_current->arch.priv_stack_end =
+		_current->arch.priv_stack_start + CONFIG_PRIVILEGED_STACK_SIZE;
 #endif
 
 	z_arm_userspace_enter(user_entry, p1, p2, p3,
-			     (uint32_t)arch_current_thread()->stack_info.start,
-			     arch_current_thread()->stack_info.size -
-			     arch_current_thread()->stack_info.delta);
+			     (uint32_t)_current->stack_info.start,
+			     _current->stack_info.size -
+			     _current->stack_info.delta);
 	CODE_UNREACHABLE;
 }
 
@@ -304,7 +304,7 @@ EXPORT_SYMBOL(z_arm_thread_is_in_user_mode);
 uint32_t z_check_thread_stack_fail(const uint32_t fault_addr, const uint32_t psp)
 {
 #if defined(CONFIG_MULTITHREADING)
-	const struct k_thread *thread = arch_current_thread();
+	const struct k_thread *thread = _current;
 
 	if (thread == NULL) {
 		return 0;
@@ -314,7 +314,7 @@ uint32_t z_check_thread_stack_fail(const uint32_t fault_addr, const uint32_t psp
 #if (defined(CONFIG_FPU) && defined(CONFIG_FPU_SHARING)) && \
 	defined(CONFIG_MPU_STACK_GUARD)
 	uint32_t guard_len =
-		((arch_current_thread()->arch.mode & Z_ARM_MODE_MPU_GUARD_FLOAT_Msk) != 0) ?
+		((_current->arch.mode & Z_ARM_MODE_MPU_GUARD_FLOAT_Msk) != 0) ?
 		MPU_GUARD_ALIGN_AND_SIZE_FLOAT : MPU_GUARD_ALIGN_AND_SIZE;
 #else
 	/* If MPU_STACK_GUARD is not enabled, the guard length is
@@ -377,7 +377,7 @@ uint32_t z_check_thread_stack_fail(const uint32_t fault_addr, const uint32_t psp
 #if defined(CONFIG_FPU) && defined(CONFIG_FPU_SHARING)
 int arch_float_disable(struct k_thread *thread)
 {
-	if (thread != arch_current_thread()) {
+	if (thread != _current) {
 		return -EINVAL;
 	}
 

arch/arm/core/cortex_m/swap_helper.S

@@ -288,7 +288,7 @@ in_fp_endif:
 #if defined(CONFIG_MPU_STACK_GUARD) || defined(CONFIG_USERSPACE)
     /* Re-program dynamic memory map */
     push {r2,lr}
-    mov r0, r2 /* arch_current_thread() thread */
+    mov r0, r2 /* _current thread */
     bl z_arm_configure_dynamic_mpu_regions
     pop {r2,lr}
 #endif

arch/arm/core/cortex_m/thread.c

@@ -231,8 +231,8 @@ FUNC_NORETURN void arch_user_mode_enter(k_thread_entry_t user_entry,
 {
 
 	/* Set up privileged stack before entering user mode */
-	arch_current_thread()->arch.priv_stack_start =
-		(uint32_t)z_priv_stack_find(arch_current_thread()->stack_obj);
+	_current->arch.priv_stack_start =
+		(uint32_t)z_priv_stack_find(_current->stack_obj);
 #if defined(CONFIG_MPU_STACK_GUARD)
 #if defined(CONFIG_THREAD_STACK_INFO)
 	/* We're dropping to user mode which means the guard area is no
@@ -241,32 +241,32 @@ FUNC_NORETURN void arch_user_mode_enter(k_thread_entry_t user_entry,
 	 * which accounted for memory borrowed from the thread stack.
 	 */
 #if FP_GUARD_EXTRA_SIZE > 0
-	if ((arch_current_thread()->arch.mode & Z_ARM_MODE_MPU_GUARD_FLOAT_Msk) != 0) {
-		arch_current_thread()->stack_info.start -= FP_GUARD_EXTRA_SIZE;
-		arch_current_thread()->stack_info.size += FP_GUARD_EXTRA_SIZE;
+	if ((_current->arch.mode & Z_ARM_MODE_MPU_GUARD_FLOAT_Msk) != 0) {
+		_current->stack_info.start -= FP_GUARD_EXTRA_SIZE;
+		_current->stack_info.size += FP_GUARD_EXTRA_SIZE;
 	}
 #endif /* FP_GUARD_EXTRA_SIZE */
-	arch_current_thread()->stack_info.start -= MPU_GUARD_ALIGN_AND_SIZE;
-	arch_current_thread()->stack_info.size += MPU_GUARD_ALIGN_AND_SIZE;
+	_current->stack_info.start -= MPU_GUARD_ALIGN_AND_SIZE;
+	_current->stack_info.size += MPU_GUARD_ALIGN_AND_SIZE;
 #endif /* CONFIG_THREAD_STACK_INFO */
 
 	/* Stack guard area reserved at the bottom of the thread's
 	 * privileged stack. Adjust the available (writable) stack
 	 * buffer area accordingly.
 	 */
 #if defined(CONFIG_FPU) && defined(CONFIG_FPU_SHARING)
-	arch_current_thread()->arch.priv_stack_start +=
-		((arch_current_thread()->arch.mode & Z_ARM_MODE_MPU_GUARD_FLOAT_Msk) != 0) ?
+	_current->arch.priv_stack_start +=
+		((_current->arch.mode & Z_ARM_MODE_MPU_GUARD_FLOAT_Msk) != 0) ?
 		MPU_GUARD_ALIGN_AND_SIZE_FLOAT : MPU_GUARD_ALIGN_AND_SIZE;
 #else
-	arch_current_thread()->arch.priv_stack_start += MPU_GUARD_ALIGN_AND_SIZE;
+	_current->arch.priv_stack_start += MPU_GUARD_ALIGN_AND_SIZE;
 #endif /* CONFIG_FPU && CONFIG_FPU_SHARING */
 #endif /* CONFIG_MPU_STACK_GUARD */
 
 	z_arm_userspace_enter(user_entry, p1, p2, p3,
-			     (uint32_t)arch_current_thread()->stack_info.start,
-			     arch_current_thread()->stack_info.size -
-			     arch_current_thread()->stack_info.delta);
+			     (uint32_t)_current->stack_info.start,
+			     _current->stack_info.size -
+			     _current->stack_info.delta);
 	CODE_UNREACHABLE;
 }
 
@@ -379,7 +379,7 @@ void configure_builtin_stack_guard(struct k_thread *thread)
 uint32_t z_check_thread_stack_fail(const uint32_t fault_addr, const uint32_t psp)
 {
 #if defined(CONFIG_MULTITHREADING)
-	const struct k_thread *thread = arch_current_thread();
+	const struct k_thread *thread = _current;
 
 	if (thread == NULL) {
 		return 0;
@@ -389,7 +389,7 @@ uint32_t z_check_thread_stack_fail(const uint32_t fault_addr, const uint32_t psp
 #if (defined(CONFIG_FPU) && defined(CONFIG_FPU_SHARING)) && \
 	defined(CONFIG_MPU_STACK_GUARD)
 	uint32_t guard_len =
-		((arch_current_thread()->arch.mode & Z_ARM_MODE_MPU_GUARD_FLOAT_Msk) != 0) ?
+		((_current->arch.mode & Z_ARM_MODE_MPU_GUARD_FLOAT_Msk) != 0) ?
 		MPU_GUARD_ALIGN_AND_SIZE_FLOAT : MPU_GUARD_ALIGN_AND_SIZE;
 #else
 	/* If MPU_STACK_GUARD is not enabled, the guard length is
@@ -452,7 +452,7 @@ uint32_t z_check_thread_stack_fail(const uint32_t fault_addr, const uint32_t psp
 #if defined(CONFIG_FPU) && defined(CONFIG_FPU_SHARING)
 int arch_float_disable(struct k_thread *thread)
 {
-	if (thread != arch_current_thread()) {
+	if (thread != _current) {
 		return -EINVAL;
 	}