[PATCH] Re: How to completely disable async fastboot?

[Jeff Garzik]

Arjan van de Ven wrote:
> On Wed, 15 Apr 2009 20:20:32 -0400
> Jeff Garzik <jeff@xxxxxxxxxx> wrote:
>
> > The following commit
> >
> > > commit 9710794383ee5008d67f1a6613a4717bf6de47bc
> > > Author: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
> > > Date:   Sun Mar 15 11:11:44 2009 -0700
> > >
> > >     async: remove the temporary (2.6.29) "async is off by default"
> > > code
> > not only changes a default, it completely removes the ability to turn 
> > off async AFAICS.
>
> this is on the request of Andrew and others who want to be able to use
> these API's (soon) in an "forced offload" scenario. 
>
> > At present, I need to turn this off to debug boot-time operation.
>
> can you give some details? Maybe I can help suggest things...

Too much shit is occurring in parallel, which completely obscures the 
operation of the driver I am currently debugging.  A new and unwelcome 
behavior, as it is directly impacting workflow.

Commit 9710794383ee5008d67f1a6613a4717bf6de47bc was fine for the normal 
case, but please have pity on developers!  Just like many multi-threaded 
userland programs have an option to run single-threaded (usually for 
debug purposes), the kernel should have this too.

I need a slowboot option, like the attached patch.

The patch is basically the reverse of your 
9710794383ee5008d67f1a6613a4717bf6de47bc in a different way.

	Jeff



diff --git a/kernel/async.c b/kernel/async.c
index 968ef94..8c553ce 100644
--- a/kernel/async.c
+++ b/kernel/async.c
@@ -68,6 +68,7 @@ static LIST_HEAD(async_running);
 static DEFINE_SPINLOCK(async_lock);
 
 static int async_enabled = 0;
+static int async_disabled;
 
 struct async_entry {
 	struct list_head list;
@@ -388,6 +389,11 @@ static int async_manager_thread(void *unused)
 
 static int __init async_init(void)
 {
+	if (async_disabled) {
+		async_enabled = 0;
+		return 0;
+	}
+
 	async_enabled =
 		!IS_ERR(kthread_run(async_manager_thread, NULL, "async/mgr"));
 
@@ -395,4 +401,12 @@ static int __init async_init(void)
 	return 0;
 }
 
+static int __init setup_async(char *str)
+{
+	async_disabled = 1;
+	return 1;
+}
+
+__setup("slowboot", setup_async);
+
 core_initcall(async_init);