From: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Date: Sun, 23 May 2010 07:14:08 +0000 (-0700)
Subject: iwlwifi: move sysfs_create_group to post request firmware
X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=7d47618a2ade0cb6d8a0b2597029c383c1662fa0;hp=7d47618a2ade0cb6d8a0b2597029c383c1662fa0;p=deliverable%2Flinux.git

iwlwifi: move sysfs_create_group to post request firmware

Move the sysfs_create_group to iwl_ucode_callback after we
have safely got the firmware.

The motivation to do this comes from a warning from lockdep which detected
that we request priv->mutex while holding s_active during a sysfs request
(show_statistics in the example copy pasted). The reverse order exists upon
request_firmware: request_firmware which is a sysfs operation
that requires s_active is run under priv->mutex.

This ensures that we don't get sysfs request before we finish to request
the firmware, avoiding this deadlock.

=======================================================
[ INFO: possible circular locking dependency detected ]
-------------------------------------------------------
cat/2595 is trying to acquire lock:
 (&priv->mutex){+.+.+.}, at: [<facfa598>] show_statistics+0x48/0x100 [iwlagn]

but task is already holding lock:
 (s_active){++++.+}, at: [<c0580ebd>] sysfs_get_active_two+0x1d/0x50

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (s_active){++++.+}:
       [<c0489b74>] __lock_acquire+0xc44/0x1230
       [<c048a1ed>] lock_acquire+0x8d/0x110
       [<c0581499>] sysfs_addrm_finish+0xe9/0x180
       [<c057f64a>] sysfs_hash_and_remove+0x4a/0x80
       [<c05829d4>] sysfs_remove_group+0x44/0xd0
       [<c0714b75>] dpm_sysfs_remove+0x15/0x20
       [<c070dac8>] device_del+0x38/0x170
       [<c070dc1e>] device_unregister+0x1e/0x60
       [<c071838d>] _request_firmware+0x29d/0x550
       [<c07186c7>] request_firmware+0x17/0x20
       [<fad01bf1>] iwl_mac_start+0xb1/0x1230 [iwlagn]
       [<fa46ba06>] ieee80211_open+0x436/0x6f0 [mac80211]
       [<c0808cd2>] dev_open+0x92/0xf0
       [<c0808b2b>] dev_change_flags+0x7b/0x190
       [<c08148e8>] do_setlink+0x178/0x3b0
       [<c0815169>] rtnl_setlink+0xf9/0x130
       [<c081453b>] rtnetlink_rcv_msg+0x1bb/0x1f0
       [<c0827ce6>] netlink_rcv_skb+0x86/0xa0
       [<c081436c>] rtnetlink_rcv+0x1c/0x30
       [<c08279c3>] netlink_unicast+0x263/0x290
       [<c0828768>] netlink_sendmsg+0x1c8/0x2a0
       [<c07f85fd>] sock_sendmsg+0xcd/0x100
       [<c07f964d>] sys_sendmsg+0x15d/0x290
       [<c07f9e6b>] sys_socketcall+0xeb/0x2a0
       [<c040ad9f>] sysenter_do_call+0x12/0x38

-> #0 (&priv->mutex){+.+.+.}:
       [<c0489f84>] __lock_acquire+0x1054/0x1230
       [<c048a1ed>] lock_acquire+0x8d/0x110
       [<c08bb358>] __mutex_lock_common+0x58/0x470
       [<c08bb84a>] mutex_lock_nested+0x3a/0x50
       [<facfa598>] show_statistics+0x48/0x100 [iwlagn]
       [<c070d219>] dev_attr_show+0x29/0x50
       [<c057fecd>] sysfs_read_file+0xdd/0x190
       [<c052880f>] vfs_read+0x9f/0x190
       [<c0528d22>] sys_read+0x42/0x70
       [<c040ad9f>] sysenter_do_call+0x12/0x38

other info that might help us debug this:

3 locks held by cat/2595:
 #0:  (&buffer->mutex){+.+.+.}, at: [<c057fe25>] sysfs_read_file+0x35/0x190
 #1:  (s_active){++++.+}, at: [<c0580ecd>] sysfs_get_active_two+0x2d/0x50
 #2:  (s_active){++++.+}, at: [<c0580ebd>] sysfs_get_active_two+0x1d/0x50

stack backtrace:
Pid: 2595, comm: cat Not tainted 2.6.33-tp-rc4 #2
Call Trace:
 [<c08b99ab>] ? printk+0x1d/0x22
 [<c0487752>] print_circular_bug+0xc2/0xd0
 [<c0489f84>] __lock_acquire+0x1054/0x1230
 [<c0478d81>] ? sched_clock_cpu+0x121/0x180
 [<c048a1ed>] lock_acquire+0x8d/0x110
 [<facfa598>] ? show_statistics+0x48/0x100 [iwlagn]
 [<c08bb358>] __mutex_lock_common+0x58/0x470
 [<facfa598>] ? show_statistics+0x48/0x100 [iwlagn]
 [<c08bb84a>] mutex_lock_nested+0x3a/0x50
 [<facfa598>] ? show_statistics+0x48/0x100 [iwlagn]
 [<facfa598>] show_statistics+0x48/0x100 [iwlagn]
 [<c0580cf9>] ? sysfs_get_active+0x69/0xb0
 [<facfa550>] ? show_statistics+0x0/0x100 [iwlagn]
 [<c070d219>] dev_attr_show+0x29/0x50
 [<c057fecd>] sysfs_read_file+0xdd/0x190
 [<c05ff314>] ? security_file_permission+0x14/0x20
 [<c0528242>] ? rw_verify_area+0x62/0xd0
 [<c052880f>] vfs_read+0x9f/0x190
 [<c047745b>] ? up_read+0x1b/0x30
 [<c057fdf0>] ? sysfs_read_file+0x0/0x190
 [<c04af3b4>] ? audit_syscall_entry+0x1f4/0x220
 [<c0528d22>] sys_read+0x42/0x70
 [<c040ad9f>] sysenter_do_call+0x12/0x38

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
---