RE: [PATCH] Hotplug CPU prep III: daemonize idle tasks

["BALBIR SINGH" <balbir.singh@wipro.com>]

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I tried a version of __daemonize in 2.4. It panics in
schedule()

        prepare_to_switch();
        {
                struct mm_struct *mm = next->mm;
                struct mm_struct *oldmm = prev->active_mm;
                if (!mm) {
                        if (next->active_mm) BUG();

I got hit by the BUG() in 2.4, I think prepare_to_switch has
moved to specific archs in 2.5. A quick look showed that
this issue no longer exists in 2.5.

Comments,
Balbir Singh.

|-----Original Message-----
|From: linux-kernel-owner@vger.kernel.org
|[mailto:linux-kernel-owner@vger.kernel.org]On Behalf Of Rusty Russell
|Sent: Thursday, May 09, 2002 2:20 PM
|To: torvalds@transmeta.com
|Cc: linux-kernel@vger.kernel.org
|Subject: [PATCH] Hotplug CPU prep III: daemonize idle tasks
|
|
|This patch introduces __daemonize(task), so idle tasks can be detached
|after cloning (required for late creation of idle tasks).
|
|This is independent of the last two patches.
|
|Name: Daemonize idle task
|Author: Rusty Russell
|
|D: This patch allows daemonize() to be called on another process (if
|D: not started yet), and calls it on the idle task.
|
|diff -urN -I \$.*\$ --exclude TAGS -X 
|/home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal 
|working-2.5.14-dofork+clonepid/include/linux/sched.h 
|tmp/include/linux/sched.h
|--- working-2.5.14-dofork+clonepid/include/linux/sched.h	Thu 
|May  9 18:25:21 2002
|+++ tmp/include/linux/sched.h	Thu May  9 18:36:17 2002
|@@ -654,7 +654,12 @@
| extern void exit_sighand(struct task_struct *);
| 
| extern void reparent_to_init(void);
|-extern void daemonize(void);
|+extern void __daemonize(struct task_struct *);
|+static inline void daemonize(void)
|+{
|+	__daemonize(current);
|+}
|+
| extern task_t *child_reaper;
| 
| extern int do_execve(char *, char **, char **, struct pt_regs *);
|diff -urN -I \$.*\$ --exclude TAGS -X 
|/home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal 
|working-2.5.14-dofork+clonepid/kernel/exit.c tmp/kernel/exit.c
|--- working-2.5.14-dofork+clonepid/kernel/exit.c	Mon Apr 29 
|16:00:29 2002
|+++ tmp/kernel/exit.c	Thu May  9 18:36:17 2002
|@@ -201,32 +201,30 @@
|  *	Put all the gunge required to become a kernel thread without
|  *	attached user resources in one place where it belongs.
|  */
|-
|-void daemonize(void)
|+void __daemonize(struct task_struct *tsk)
| {
| 	struct fs_struct *fs;
| 
|-
| 	/*
| 	 * If we were started as result of loading a module, close 
|all of the
| 	 * user space pages.  We don't need them, and if we didn't 
|close them
| 	 * they would be locked into memory.
| 	 */
|-	exit_mm(current);
|+	exit_mm(tsk);
| 
|-	current->session = 1;
|-	current->pgrp = 1;
|-	current->tty = NULL;
|+	tsk->session = 1;
|+	tsk->pgrp = 1;
|+	tsk->tty = NULL;
| 
| 	/* Become as one with the init task */
| 
|-	exit_fs(current);	/* current->fs->count--; */
|+	exit_fs(tsk);	/* current->fs->count--; */
| 	fs = init_task.fs;
|-	current->fs = fs;
|+	tsk->fs = fs;
| 	atomic_inc(&fs->count);
|- 	exit_files(current);
|-	current->files = init_task.files;
|-	atomic_inc(&current->files->count);
|+ 	exit_files(tsk);
|+	tsk->files = init_task.files;
|+	atomic_inc(&tsk->files->count);
| }
| 
| /*
|diff -urN -I \$.*\$ --exclude TAGS -X 
|/home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal 
|working-2.5.14-dofork+clonepid/kernel/sched.c tmp/kernel/sched.c
|--- working-2.5.14-dofork+clonepid/kernel/sched.c	Wed May  1 
|15:09:29 2002
|+++ tmp/kernel/sched.c	Thu May  9 18:45:17 2002
|@@ -1555,6 +1555,8 @@
| 	runqueue_t *idle_rq = cpu_rq(cpu), *rq = 
|cpu_rq(idle->thread_info->cpu);
| 	unsigned long flags;
| 
|+	if (idle != &init_task)
|+		__daemonize(idle);
| 	__save_flags(flags);
| 	__cli();
| 	double_rq_lock(idle_rq, rq);
|
|--
|  Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
|-
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