linux-kernel - [patch] driver core: if built-in, do not wait in driver

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Date:	Sun, 1 Apr 2007 19:35:08 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Pavel Machek <pavel@....cz>, Adrian Bunk <bunk@...sta.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Greg Kroah-Hartman <gregkh@...e.de>
Subject: [patch] driver core: if built-in, do not wait in driver_unregister()


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> I would suggest that for 2.6.21, the minimal fix is actually something 
> like the appended. Comments? Ingo, does this fix things for you?

yeah - it does the trick: i just booted the .config in question and your 
patch works fine and the bootup does not hang in slgt_init() anymore:

 Calling initcall 0xc1e78d86: slgt_init+0x0/0x1ee()
 SyncLink GT $Revision: 4.36 $
 SyncLink GT no devices found
 initcall 0xc1e78d86: slgt_init+0x0/0x1ee() returned -19
 Calling initcall 0xc1e78f74: n_hdlc_init+0x0/0x9c()
 HDLC line discipline: version $Revision: 4.8 $, maxframe=4096
 N_HDLC line discipline registered.
 initcall 0xc1e78f74: n_hdlc_init+0x0/0x9c() returned 0

thanks! Find below the full patch with metadata filled in (no other 
changes).

	Ingo

------------------------->
Subject: [patch] driver core: if built-in, do not wait in driver_unregister()
From: Linus Torvalds <torvalds@...ux-foundation.org>

built-in drivers suffered bootup hangs with certain driver unregistry
sequences, due to sysfs breakage.

do the minimal fix for v2.6.21: only wait if the driver is a module.

Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 drivers/base/driver.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

Index: linux/drivers/base/driver.c
===================================================================
--- linux.orig/drivers/base/driver.c
+++ linux/drivers/base/driver.c
@@ -183,7 +183,14 @@ int driver_register(struct device_driver
 void driver_unregister(struct device_driver * drv)
 {
 	bus_remove_driver(drv);
-	wait_for_completion(&drv->unloaded);
+	/*
+	 * If the driver is a module, we are probably in
+	 * the module unload path, and we want to wait
+	 * for everything to unload before we can actually
+	 * finish the unload.
+	 */
+	if (drv->owner)
+		wait_for_completion(&drv->unloaded);
 }
 
 /**
-
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