As register sg_interface, the sg_add will be called, which then will add device to sg_sysfs_class. This will cause lockdep warning, please see following email In this case the locks are from diffrent classi, one is sdev_class, another is sg_sysfs_class Here reclassify the sg_sysfs_class for lockdep Date: Wed, 14 May 2008 08:56:39 -0700 From: Greg KH <greg@xxxxxxxxx> To: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Dave Young <hidave.darkstar@xxxxxxxxx> Cc: linux-scsi@xxxxxxxxxxxxxxx, Kay Sievers <kay.sievers@xxxxxxxx> Subject: Re: lockdep whine in 2.6.26-rc2-mm1 Message-ID: <20080514155639.GB28594@xxxxxxxxx> References: <20080514000933.56adc131.akpm@xxxxxxxxxxxxxxxxxxxx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080514000933.56adc131.akpm@xxxxxxxxxxxxxxxxxxxx> User-Agent: Mutt/1.5.16 (2007-06-09) On Wed, May 14, 2008 at 12:09:33AM -0700, Andrew Morton wrote: > > ============================================= > [ INFO: possible recursive locking detected ] > 2.6.26-rc2-mm1 #15 > --------------------------------------------- > modprobe/942 is trying to acquire lock: > (&cls->mutex){--..}, at: [<ffffffff811b431e>] device_add+0x43d/0x57a > > but task is already holding lock: > (&cls->mutex){--..}, at: [<ffffffff811b6787>] class_interface_register+0x48/0xbd > > other info that might help us debug this: > 1 lock held by modprobe/942: > #0: (&cls->mutex){--..}, at: [<ffffffff811b6787>] class_interface_register+0x48/0xbd > > stack backtrace: > Pid: 942, comm: modprobe Not tainted 2.6.26-rc2-mm1 #15 > > Call Trace: > [<ffffffff81056be1>] __lock_acquire+0x90d/0xc50 > [<ffffffff8100c50f>] ? restore_args+0x0/0x30 > [<ffffffff811b431e>] ? device_add+0x43d/0x57a > [<ffffffff81057276>] lock_acquire+0x91/0xb7 > [<ffffffff811b431e>] ? device_add+0x43d/0x57a > [<ffffffff812b23ab>] mutex_lock_nested+0xf2/0x278 > [<ffffffff811b431e>] ? device_add+0x43d/0x57a > [<ffffffff812b3acd>] ? _spin_unlock+0x23/0x28 > [<ffffffff811b431e>] device_add+0x43d/0x57a > [<ffffffff811b4471>] device_register+0x16/0x1b > [<ffffffff811b4555>] device_create+0xdf/0x112 > [<ffffffff81055fdc>] ? trace_hardirqs_on+0xd/0xf > [<ffffffff81055fdc>] ? trace_hardirqs_on+0xd/0xf > [<ffffffff812b1fe1>] ? mutex_unlock+0x9/0xb > [<ffffffff811b79b7>] ? kobj_map+0x113/0x124 > [<ffffffff810ac0f5>] ? exact_lock+0x0/0x14 > [<ffffffff810abd09>] ? exact_match+0x0/0x9 > [<ffffffffa00ec448>] :sg:sg_add+0x2a3/0x3bd > [<ffffffff811b67b6>] class_interface_register+0x77/0xbd > [<ffffffffa005d869>] :scsi_mod:scsi_register_interface+0x11/0x13 > [<ffffffffa00d50a3>] :sg:init_sg+0xa3/0x155 > [<ffffffff8105ea8f>] sys_init_module+0x1823/0x197a > [<ffffffff810c45bc>] ? seq_release+0x0/0x56 > [<ffffffff8100bebb>] system_call_after_swapgs+0x7b/0x80 Signed-off-by: Dave Young <hidave.darkstar@xxxxxxxxx> --- drivers/scsi/sg.c | 6 ++++++ 1 file changed, 6 insertions(+) diff -upr linux/drivers/scsi/sg.c linux.new/drivers/scsi/sg.c --- linux/drivers/scsi/sg.c 2008-05-27 17:09:42.000000000 +0800 +++ linux.new/drivers/scsi/sg.c 2008-05-27 17:09:51.000000000 +0800 @@ -49,6 +49,7 @@ static int sg_version_num = 30534; /* 2 #include <linux/delay.h> #include <linux/scatterlist.h> #include <linux/blktrace_api.h> +#include <linux/lockdep.h> #include "scsi.h" #include <scsi/scsi_dbg.h> @@ -67,6 +68,8 @@ static int sg_proc_init(void); static void sg_proc_cleanup(void); #endif +static struct lock_class_key sg_class_key; + #define SG_ALLOW_DIO_DEF 0 #define SG_ALLOW_DIO_CODE /* compile out by commenting this define */ @@ -1579,6 +1582,9 @@ init_sg(void) rc = PTR_ERR(sg_sysfs_class); goto err_out; } + + lockdep_set_class_and_name(&sg_sysfs_class->mutex, &sg_class_key, + sg_sysfs_class->name); sg_sysfs_valid = 1; rc = scsi_register_interface(&sg_interface); if (0 == rc) { -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html