s390: switch to generic kernel_thread()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 34 insertions, 40 deletions

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 107610e01a29..57442393bac7 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -125,6 +125,7 @@ config S390
         select GENERIC_CLOCKEVENTS
         select KTIME_SCALAR if 32BIT
         select HAVE_ARCH_SECCOMP_FILTER
+        select GENERIC_KERNEL_THREAD
 
 config SCHED_OMIT_FRAME_POINTER
         def_bool y
diff --git a/arch/s390/include/asm/processor.h b/arch/s390/include/asm/processor.h
index 0bc77619c3a3..da6f5baeee5c 100644
--- a/arch/s390/include/asm/processor.h
+++ b/arch/s390/include/asm/processor.h
@@ -135,7 +135,6 @@ struct seq_file;
 
 /* Free all resources held by a thread. */
 extern void release_thread(struct task_struct *);
-extern int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags);
 
 /*
  * Return saved PC of a blocked thread.
diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index 2868a364ff94..bab088de4569 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -98,25 +98,6 @@ void cpu_idle(void)
 
 extern void __kprobes kernel_thread_starter(void);
 
-int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
-{
-        struct pt_regs regs;
-
-        memset(&regs, 0, sizeof(regs));
-        regs.psw.mask = psw_kernel_bits |
-                PSW_MASK_DAT | PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
-        regs.psw.addr = (unsigned long) kernel_thread_starter | PSW_ADDR_AMODE;
-        regs.gprs[9] = (unsigned long) fn;
-        regs.gprs[10] = (unsigned long) arg;
-        regs.gprs[11] = (unsigned long) do_exit;
-        regs.orig_gpr2 = -1;
-
-        /* Ok, create the new process.. */
-        return do_fork(flags | CLONE_VM | CLONE_UNTRACED,
-                       0, &regs, 0, NULL, NULL);
-}
-EXPORT_SYMBOL(kernel_thread);
-
 /*
  * Free current thread data structures etc..
  */
@@ -133,7 +114,7 @@ void release_thread(struct task_struct *dead_task)
 }
 
 int copy_thread(unsigned long clone_flags, unsigned long new_stackp,
-                unsigned long unused,
+                unsigned long arg,
                 struct task_struct *p, struct pt_regs *regs)
 {
         struct thread_info *ti;
@@ -145,20 +126,44 @@ int copy_thread(unsigned long clone_flags, unsigned long new_stackp,
 
         frame = container_of(task_pt_regs(p), struct fake_frame, childregs);
         p->thread.ksp = (unsigned long) frame;
-        /* Store access registers to kernel stack of new process. */
-        frame->childregs = *regs;
-        frame->childregs.gprs[2] = 0;   /* child returns 0 on fork. */
-        frame->childregs.gprs[15] = new_stackp;
-        frame->sf.back_chain = 0;
+        /* Save access registers to new thread structure. */
+        save_access_regs(&p->thread.acrs[0]);
+        /* start new process with ar4 pointing to the correct address space */
+        p->thread.mm_segment = get_fs();
+        /* Don't copy debug registers */
+        memset(&p->thread.per_user, 0, sizeof(p->thread.per_user));
+        memset(&p->thread.per_event, 0, sizeof(p->thread.per_event));
+        clear_tsk_thread_flag(p, TIF_SINGLE_STEP);
+        clear_tsk_thread_flag(p, TIF_PER_TRAP);
+        /* Initialize per thread user and system timer values */
+        ti = task_thread_info(p);
+        ti->user_timer = 0;
+        ti->system_timer = 0;
 
+        frame->sf.back_chain = 0;
         /* new return point is ret_from_fork */
         frame->sf.gprs[8] = (unsigned long) ret_from_fork;
-
         /* fake return stack for resume(), don't go back to schedule */
         frame->sf.gprs[9] = (unsigned long) frame;
 
-        /* Save access registers to new thread structure. */
-        save_access_regs(&p->thread.acrs[0]);
+        /* Store access registers to kernel stack of new process. */
+        if (unlikely(!regs)) {
+                /* kernel thread */
+                memset(&frame->childregs, 0, sizeof(struct pt_regs));
+                frame->childregs.psw.mask = psw_kernel_bits | PSW_MASK_DAT |
+                                PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
+                frame->childregs.psw.addr = PSW_ADDR_AMODE |
+                                (unsigned long) kernel_thread_starter;
+                frame->childregs.gprs[9] = new_stackp; /* function */
+                frame->childregs.gprs[10] = arg;
+                frame->childregs.gprs[11] = (unsigned long) do_exit;
+                frame->childregs.orig_gpr2 = -1;
+
+                return 0;
+        }
+        frame->childregs = *regs;
+        frame->childregs.gprs[2] = 0;   /* child returns 0 on fork. */
+        frame->childregs.gprs[15] = new_stackp;
 
 #ifndef CONFIG_64BIT
         /*
@@ -184,17 +189,6 @@ int copy_thread(unsigned long clone_flags, unsigned long new_stackp,
                 }
         }
 #endif /* CONFIG_64BIT */
-        /* start new process with ar4 pointing to the correct address space */
-        p->thread.mm_segment = get_fs();
-        /* Don't copy debug registers */
-        memset(&p->thread.per_user, 0, sizeof(p->thread.per_user));
-        memset(&p->thread.per_event, 0, sizeof(p->thread.per_event));
-        clear_tsk_thread_flag(p, TIF_SINGLE_STEP);
-        clear_tsk_thread_flag(p, TIF_PER_TRAP);
-        /* Initialize per thread user and system timer values */
-        ti = task_thread_info(p);
-        ti->user_timer = 0;
-        ti->system_timer = 0;
         return 0;
 }