linux-kernel - [RFC PATCH v1 29/31] ARC: switch to generic kernel

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Date:	Wed,  7 Nov 2012 10:47:52 +0100
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	tglx@...utronix.de, arnd@...db.de,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>
Subject: [RFC PATCH v1 29/31] ARC: switch to generic kernel_thread()

Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
---
 arch/arc/Kconfig          |    1 +
 arch/arc/kernel/process.c |   29 +++++++++--------------------
 2 files changed, 10 insertions(+), 20 deletions(-)

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index d6983afa..f3aacfc 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -17,6 +17,7 @@ config ARC
 	select GENERIC_FIND_FIRST_BIT
 	# for now, we don't need GENERIC_IRQ_PROBE, CONFIG_GENERIC_IRQ_CHIP
 	select GENERIC_IRQ_SHOW
+	select GENERIC_KERNEL_THREAD
 	select GENERIC_PENDING_IRQ if SMP
 	select GENERIC_SMP_IDLE_THREAD
 	select HAVE_GENERIC_HARDIRQS
diff --git a/arch/arc/kernel/process.c b/arch/arc/kernel/process.c
index fee3e11..d2bb27f 100644
--- a/arch/arc/kernel/process.c
+++ b/arch/arc/kernel/process.c
@@ -142,22 +142,6 @@ void cpu_idle(void)
 	}
 }
 
-int kernel_thread(int (*fn) (void *), void *arg, unsigned long flags)
-{
-	struct pt_regs regs = {
-		.r0 = (unsigned long)arg,
-		.r1 = (unsigned long)fn
-	};
-
-	regs.status32 = read_aux_reg(0xa);
-
-	/* Ok, create the new process.. */
-	return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL,
-		       NULL);
-
-}
-EXPORT_SYMBOL(kernel_thread);
-
 asmlinkage void ret_from_fork(void);
 asmlinkage void ret_from_kernel_thread(void) __attribute__((noreturn));
 
@@ -192,7 +176,7 @@ asmlinkage void ret_from_kernel_thread(void) __attribute__((noreturn));
  * ------------------  <===== END of PAGE
  */
 int copy_thread(unsigned long clone_flags,
-		unsigned long usp, unsigned long topstk,
+		unsigned long usp, unsigned long arg,
 		struct task_struct *p, struct pt_regs *regs)
 {
 	struct pt_regs *c_regs;        /* child's pt_regs */
@@ -213,10 +197,12 @@ int copy_thread(unsigned long clone_flags,
 	 */
 	p->thread.ksp = (unsigned long)c_callee;	/* THREAD_KSP */
 
-	/* Copy parents pt regs on child's kernel mode stack */
-	*c_regs = *regs;
+	if (unlikely(p->flags & PF_KTHREAD)) {
+		memset(c_regs, 0, sizeof(struct pt_regs));
+		c_regs->r0 = arg; /* argument to kernel thread */
+		c_regs->r1 = usp;  /* function */
+		c_regs->status32 = read_aux_reg(0xa);
 
-	if (!(user_mode(regs))) {
 		c_regs->sp =
 		    (unsigned long)task_thread_info(p) + (THREAD_SIZE - 4);
 
@@ -232,6 +218,9 @@ int copy_thread(unsigned long clone_flags,
 	childksp[0] = 0;				/* for POP fp */
 	childksp[1] = (unsigned long)ret_from_fork;	/* for POP blink */
 
+	/* Copy parents pt regs on child's kernel mode stack */
+	*c_regs = *regs;
+
 	c_regs->sp = usp;
 	c_regs->r0 = 0;		/* fork returns 0 in child */
 
-- 
1.7.4.1

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