[PATCH] sched: consolidate CLONE_IDLETASK masking

Every arch now bears the burden of sanitizing CLONE_IDLETASK out of the
clone_flags passed to do_fork() by userspace.  This patch hoists the
masking of CLONE_IDLETASK out of the system call entrypoints into
do_fork(), and thereby removes some small overheads from do_fork(), as
do_fork() may now assume that CLONE_IDLETASK has been cleared.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/alpha/kernel/process.c

@@ -246,8 +246,7 @@ alpha_clone(unsigned long clone_flags, unsigned long usp,
 	if (!usp)
 		usp = rdusp();
 
-	return do_fork(clone_flags & ~CLONE_IDLETASK, usp, regs, 0,
-		       parent_tid, child_tid);
+	return do_fork(clone_flags, usp, regs, 0, parent_tid, child_tid);
 }
 
 int

arch/arm/kernel/sys_arm.c

@@ -257,7 +257,7 @@ asmlinkage int sys_clone(unsigned long clone_flags, unsigned long newsp, struct
 	if (!newsp)
 		newsp = regs->ARM_sp;
 
-	return do_fork(clone_flags & ~CLONE_IDLETASK, newsp, regs, 0, NULL, NULL);
+	return do_fork(clone_flags, newsp, regs, 0, NULL, NULL);
 }
 
 asmlinkage int sys_vfork(struct pt_regs *regs)

arch/arm26/kernel/sys_arm.c

@@ -256,7 +256,7 @@ asmlinkage int sys_clone(unsigned long clone_flags, unsigned long newsp, struct
 	if (!newsp)
 		newsp = regs->ARM_sp;
 
-	return do_fork(clone_flags & ~CLONE_IDLETASK, newsp, regs, 0, NULL, NULL);
+	return do_fork(clone_flags, newsp, regs, 0, NULL, NULL);
 }
 
 asmlinkage int sys_vfork(struct pt_regs *regs)

arch/cris/arch-v10/kernel/process.c

@@ -180,7 +180,7 @@ asmlinkage int sys_clone(unsigned long newusp, unsigned long flags,
 {
 	if (!newusp)
 		newusp = rdusp();
-	return do_fork(flags & ~CLONE_IDLETASK, newusp, regs, 0, parent_tid, child_tid);
+	return do_fork(flags, newusp, regs, 0, parent_tid, child_tid);
 }
 
 /* vfork is a system call in i386 because of register-pressure - maybe

arch/h8300/kernel/process.c

@@ -189,7 +189,7 @@ asmlinkage int h8300_clone(struct pt_regs *regs)
 	newsp = regs->er2;
 	if (!newsp)
 		newsp  = rdusp();
-	return do_fork(clone_flags & ~CLONE_IDLETASK, newsp, regs, 0, NULL, NULL);
+	return do_fork(clone_flags, newsp, regs, 0, NULL, NULL);
 
 }
 

arch/i386/kernel/process.c

@@ -595,7 +595,7 @@ asmlinkage int sys_clone(struct pt_regs regs)
 	child_tidptr = (int __user *)regs.edi;
 	if (!newsp)
 		newsp = regs.esp;
-	return do_fork(clone_flags & ~CLONE_IDLETASK, newsp, &regs, 0, parent_tidptr, child_tidptr);
+	return do_fork(clone_flags, newsp, &regs, 0, parent_tidptr, child_tidptr);
 }
 
 /*

arch/ia64/ia32/ia32_entry.S

@@ -41,7 +41,7 @@ ENTRY(ia32_clone)
 	zxt4 out1=in1				// newsp
 	mov out3=16				// stacksize (compensates for 16-byte scratch area)
 	adds out2=IA64_SWITCH_STACK_SIZE+16,sp	// out2 = &regs
-	dep out0=0,in0,CLONE_IDLETASK_BIT,1	// out0 = clone_flags & ~CLONE_IDLETASK
+	mov out0=in0				// out0 = clone_flags
 	zxt4 out4=in2				// out4 = parent_tidptr
 	zxt4 out5=in4				// out5 = child_tidptr
 	br.call.sptk.many rp=do_fork

arch/ia64/kernel/asm-offsets.c

@@ -195,11 +195,6 @@ void foo(void)
 	DEFINE(IA64_TIMESPEC_TV_NSEC_OFFSET, offsetof (struct timespec, tv_nsec));
 
 
-	DEFINE(CLONE_IDLETASK_BIT, 12);
-#if CLONE_IDLETASK != (1 << 12)
-# error "CLONE_IDLETASK_BIT incorrect, please fix"
-#endif
-
 	DEFINE(CLONE_SETTLS_BIT, 19);
 #if CLONE_SETTLS != (1<<19)
 # error "CLONE_SETTLS_BIT incorrect, please fix"

arch/ia64/kernel/entry.S

@@ -128,7 +128,7 @@ GLOBAL_ENTRY(sys_clone2)
 (p6)	st8 [r2]=in5				// store TLS in r16 for copy_thread()
 	mov out5=in4	// child_tidptr:  valid only w/CLONE_CHILD_SETTID or CLONE_CHILD_CLEARTID
 	adds out2=IA64_SWITCH_STACK_SIZE+16,sp	// out2 = &regs
-	dep out0=0,in0,CLONE_IDLETASK_BIT,1	// out0 = clone_flags & ~CLONE_IDLETASK
+	mov out0=in0				// out0 = clone_flags
 	br.call.sptk.many rp=do_fork
 .ret1:	.restore sp
 	adds sp=IA64_SWITCH_STACK_SIZE,sp	// pop the switch stack
@@ -157,7 +157,7 @@ GLOBAL_ENTRY(sys_clone)
 (p6)	st8 [r2]=in4				// store TLS in r13 (tp)
 	mov out5=in3	// child_tidptr:  valid only w/CLONE_CHILD_SETTID or CLONE_CHILD_CLEARTID
 	adds out2=IA64_SWITCH_STACK_SIZE+16,sp	// out2 = &regs
-	dep out0=0,in0,CLONE_IDLETASK_BIT,1	// out0 = clone_flags & ~CLONE_IDLETASK
+	mov out0=in0				// out0 = clone_flags
 	br.call.sptk.many rp=do_fork
 .ret2:	.restore sp
 	adds sp=IA64_SWITCH_STACK_SIZE,sp	// pop the switch stack

arch/m68k/kernel/process.c

@@ -232,7 +232,7 @@ asmlinkage int m68k_clone(struct pt_regs *regs)
 	child_tidptr = (int *)regs->d4;
 	if (!newsp)
 		newsp = rdusp();
-	return do_fork(clone_flags & ~CLONE_IDLETASK, newsp, regs, 0,
+	return do_fork(clone_flags, newsp, regs, 0,
 		       parent_tidptr, child_tidptr);
 }
 

arch/m68knommu/kernel/process.c

@@ -188,7 +188,7 @@ asmlinkage int m68k_clone(struct pt_regs *regs)
 	newsp = regs->d2;
 	if (!newsp)
 		newsp = rdusp();
-        return do_fork(clone_flags & ~CLONE_IDLETASK, newsp, regs, 0, NULL, NULL);
+        return do_fork(clone_flags, newsp, regs, 0, NULL, NULL);
 }
 
 int copy_thread(int nr, unsigned long clone_flags,

arch/mips/kernel/syscall.c

@@ -180,7 +180,7 @@ static_unused int _sys_clone(nabi_no_regargs struct pt_regs regs)
 		newsp = regs.regs[29];
 	parent_tidptr = (int *) regs.regs[6];
 	child_tidptr = (int *) regs.regs[7];
-	return do_fork(clone_flags & ~CLONE_IDLETASK, newsp, &regs, 0,
+	return do_fork(clone_flags, newsp, &regs, 0,
 	               parent_tidptr, child_tidptr);
 }
 

arch/parisc/kernel/process.c

@@ -262,7 +262,7 @@ sys_clone(unsigned long clone_flags, unsigned long usp,
 	if(usp == 0)
 		usp = regs->gr[30];
 
-	return do_fork(clone_flags & ~CLONE_IDLETASK, usp, regs, 0, user_tid, NULL);
+	return do_fork(clone_flags, usp, regs, 0, user_tid, NULL);
 }
 
 int

arch/ppc/kernel/process.c

@@ -555,8 +555,7 @@ int sys_clone(unsigned long clone_flags, unsigned long usp,
 	CHECK_FULL_REGS(regs);
 	if (usp == 0)
 		usp = regs->gpr[1];	/* stack pointer for child */
- 	return do_fork(clone_flags & ~CLONE_IDLETASK, usp, regs, 0,
-			parent_tidp, child_tidp);
+ 	return do_fork(clone_flags, usp, regs, 0, parent_tidp, child_tidp);
 }
 
 int sys_fork(int p1, int p2, int p3, int p4, int p5, int p6,

arch/ppc64/kernel/process.c

@@ -458,7 +458,7 @@ int sys_clone(unsigned long clone_flags, unsigned long p2, unsigned long p3,
 		}
 	}
 
-	return do_fork(clone_flags & ~CLONE_IDLETASK, p2, regs, 0,
+	return do_fork(clone_flags, p2, regs, 0,
 		    (int __user *)parent_tidptr, (int __user *)child_tidptr);
 }
 

arch/s390/kernel/compat_linux.c

@@ -1219,7 +1219,7 @@ asmlinkage long sys32_clone(struct pt_regs regs)
 	child_tidptr = (int *) (regs.gprs[5] & 0x7fffffffUL);
         if (!newsp)
                 newsp = regs.gprs[15];
-        return do_fork(clone_flags & ~CLONE_IDLETASK, newsp, &regs, 0,
+        return do_fork(clone_flags, newsp, &regs, 0,
 		       parent_tidptr, child_tidptr);
 }
 

arch/s390/kernel/process.c

@@ -336,7 +336,7 @@ asmlinkage long sys_clone(struct pt_regs regs)
 	child_tidptr = (int __user *) regs.gprs[5];
         if (!newsp)
                 newsp = regs.gprs[15];
-        return do_fork(clone_flags & ~CLONE_IDLETASK, newsp, &regs, 0,
+        return do_fork(clone_flags, newsp, &regs, 0,
 		       parent_tidptr, child_tidptr);
 }
 

arch/sh/kernel/process.c

@@ -440,7 +440,7 @@ asmlinkage int sys_clone(unsigned long clone_flags, unsigned long newsp,
 {
 	if (!newsp)
 		newsp = regs.regs[15];
-	return do_fork(clone_flags & ~CLONE_IDLETASK, newsp, &regs, 0,
+	return do_fork(clone_flags, newsp, &regs, 0,
 			(int __user *)parent_tidptr, (int __user *)child_tidptr);
 }
 

arch/sh64/kernel/process.c

@@ -820,7 +820,7 @@ asmlinkage int sys_clone(unsigned long clone_flags, unsigned long newsp,
 {
 	if (!newsp)
 		newsp = pregs->regs[15];
-	return do_fork(clone_flags & ~CLONE_IDLETASK, newsp, pregs, 0, 0, 0);
+	return do_fork(clone_flags, newsp, pregs, 0, 0, 0);
 }
 
 /*

arch/sparc/kernel/process.c

@@ -435,8 +435,6 @@ asmlinkage int sparc_do_fork(unsigned long clone_flags,
 {
 	unsigned long parent_tid_ptr, child_tid_ptr;
 
-	clone_flags &= ~CLONE_IDLETASK;
-
 	parent_tid_ptr = regs->u_regs[UREG_I2];
 	child_tid_ptr = regs->u_regs[UREG_I4];
 

arch/sparc64/kernel/process.c

@@ -588,8 +588,6 @@ asmlinkage long sparc_do_fork(unsigned long clone_flags,
 {
 	int __user *parent_tid_ptr, *child_tid_ptr;
 
-	clone_flags &= ~CLONE_IDLETASK;
-
 #ifdef CONFIG_COMPAT
 	if (test_thread_flag(TIF_32BIT)) {
 		parent_tid_ptr = compat_ptr(regs->u_regs[UREG_I2]);

arch/x86_64/ia32/sys_ia32.c

@@ -1148,8 +1148,7 @@ asmlinkage long sys32_clone(unsigned int clone_flags, unsigned int newsp,
 	void __user *child_tid = (void __user *)regs->rdi;
 	if (!newsp)
 		newsp = regs->rsp;
-        return do_fork(clone_flags & ~CLONE_IDLETASK, newsp, regs, 0,
-		    parent_tid, child_tid);
+        return do_fork(clone_flags, newsp, regs, 0, parent_tid, child_tid);
 }
 
 /*

arch/x86_64/kernel/process.c

@@ -555,8 +555,7 @@ asmlinkage long sys_clone(unsigned long clone_flags, unsigned long newsp, void _
 {
 	if (!newsp)
 		newsp = regs->rsp;
-	return do_fork(clone_flags & ~CLONE_IDLETASK, newsp, regs, 0,
-		    parent_tid, child_tid);
+	return do_fork(clone_flags, newsp, regs, 0, parent_tid, child_tid);
 }
 
 /*

include/linux/sched.h

@@ -40,7 +40,6 @@ struct exec_domain;
 #define CLONE_FS	0x00000200	/* set if fs info shared between processes */
 #define CLONE_FILES	0x00000400	/* set if open files shared between processes */
 #define CLONE_SIGHAND	0x00000800	/* set if signal handlers and blocked signals shared */
-#define CLONE_IDLETASK	0x00001000	/* set if new pid should be 0 (kernel only)*/
 #define CLONE_PTRACE	0x00002000	/* set if we want to let tracing continue on the child too */
 #define CLONE_VFORK	0x00004000	/* set if the parent wants the child to wake it up on mm_release */
 #define CLONE_PARENT	0x00008000	/* set if we want to have the same parent as the cloner */

kernel/fork.c

@@ -45,6 +45,9 @@
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 
+/* set if new pid should be 0 (kernel only)*/
+#define CLONE_IDLETASK	0x00001000
+
 /* The idle threads do not count..
  * Protected by write_lock_irq(&tasklist_lock)
  */
@@ -1194,7 +1197,7 @@ task_t * __init fork_idle(int cpu)
 
 static inline int fork_traceflag (unsigned clone_flags)
 {
-	if (clone_flags & (CLONE_UNTRACED | CLONE_IDLETASK))
+	if (clone_flags & CLONE_UNTRACED)
 		return 0;
 	else if (clone_flags & CLONE_VFORK) {
 		if (current->ptrace & PT_TRACE_VFORK)
@@ -1225,6 +1228,7 @@ long do_fork(unsigned long clone_flags,
 	int trace = 0;
 	long pid;
 
+	clone_flags &= ~CLONE_IDLETASK;
 	if (unlikely(current->ptrace)) {
 		trace = fork_traceflag (clone_flags);
 		if (trace)
@@ -1254,13 +1258,11 @@ long do_fork(unsigned long clone_flags,
 			set_tsk_thread_flag(p, TIF_SIGPENDING);
 		}
 
-		if (likely(!(clone_flags & CLONE_IDLETASK))) {
 		if (!(clone_flags & CLONE_STOPPED))
 			wake_up_new_task(p, clone_flags);
 		else
 			p->state = TASK_STOPPED;
 		++total_forks;
-		}
 
 		if (unlikely (trace)) {
 			current->ptrace_message = pid;