With 2.6.20-rc2, I got these messages in syslog recently :

Dec 28 19:33:17 brouette kernel: BUG: scheduling while atomic: hald-addon-stor/0x20000000/1552
Dec 28 19:33:17 brouette kernel:  [<c0380635>] __sched_text_start+0x615/0xafb
Dec 28 19:33:17 brouette kernel:  [<c011e47d>] tasklet_action+0x49/0xb4
Dec 28 19:33:17 brouette kernel:  [<c011e115>] __do_softirq+0x71/0xd6
Dec 28 19:33:17 brouette kernel:  [<c0105293>] do_IRQ+0x45/0x82
Dec 28 19:33:17 brouette kernel:  [<c02938c9>] ata_output_data+0x6b/0x73
Dec 28 19:33:17 brouette kernel:  [<c01035f7>] common_interrupt+0x23/0x28
Dec 28 19:33:17 brouette kernel:  [<c011527f>] __cond_resched+0x16/0x34
Dec 28 19:33:17 brouette kernel:  [<c0380b3e>] cond_resched+0x23/0x2a
Dec 28 19:33:17 brouette kernel:  [<c03822ee>] __reacquire_kernel_lock+0x1c/0x3c
Dec 28 19:33:17 brouette kernel:  [<c038065d>] __sched_text_start+0x63d/0xafb
Dec 28 19:33:17 brouette kernel:  [<c029c30e>] cdrom_start_packet_command+0xf1/0x15c
Dec 28 19:33:17 brouette kernel:  [<c029db89>] cdrom_do_pc_continuation+0x0/0x2d
Dec 28 19:33:17 brouette kernel:  [<c011527f>] __cond_resched+0x16/0x34
Dec 28 19:33:17 brouette kernel:  [<c0380b3e>] cond_resched+0x23/0x2a
Dec 28 19:33:17 brouette kernel:  [<c0380b68>] wait_for_completion+0xf/0xbc
Dec 28 19:33:17 brouette kernel:  [<c0220a22>] elv_insert+0xbb/0x141
Dec 28 19:33:17 brouette kernel:  [<c0291867>] ide_do_request+0x3f2/0x9b6
Dec 28 19:33:17 brouette kernel:  [<c0291ef2>] ide_do_drive_cmd+0xc7/0xfc
Dec 28 19:33:17 brouette kernel:  [<c029a010>] cdrom_queue_packet_command+0x30/0xad
Dec 28 19:33:17 brouette kernel:  [<c0222919>] __blk_put_request+0x26/0x7a
Dec 28 19:33:17 brouette kernel:  [<c0222b90>] blk_put_request+0x22/0x36
Dec 28 19:33:17 brouette kernel:  [<c029a331>] cdrom_check_status+0x5c/0x67
Dec 28 19:33:17 brouette kernel:  [<c0222b4b>] blk_end_sync_rq+0x0/0x23
Dec 28 19:33:17 brouette kernel:  [<c029afe0>] cdrom_read_toc+0x2e/0x455
Dec 28 19:33:17 brouette kernel:  [<c029bf63>] idecd_revalidate_disk+0x10/0x16
Dec 28 19:33:17 brouette kernel:  [<c0220000>] crypto_init_compress_ops+0x3/0x11
Dec 28 19:33:17 brouette kernel:  [<c01569c6>] get_super+0x15/0x90
Dec 28 19:33:17 brouette kernel:  [<c017515b>] __invalidate_device+0x30/0x36
Dec 28 19:33:17 brouette kernel:  [<c017519c>] check_disk_change+0x3b/0x66
Dec 28 19:33:17 brouette kernel:  [<c02c1a49>] cdrom_open+0x150/0xa6f
Dec 28 19:33:17 brouette kernel:  [<c0222b90>] blk_put_request+0x22/0x36
Dec 28 19:33:17 brouette kernel:  [<c0291f04>] ide_do_drive_cmd+0xd9/0xfc
Dec 28 19:33:17 brouette kernel:  [<c0163e36>] __d_lookup+0x83/0xf6
Dec 28 19:33:17 brouette kernel:  [<c016434f>] dput+0xb5/0x128
Dec 28 19:33:17 brouette kernel:  [<c015b175>] do_lookup+0x59/0x169
Dec 28 19:33:17 brouette kernel:  [<c019dcf0>] ext3_permission+0x0/0xa
Dec 28 19:33:17 brouette kernel:  [<c016434f>] dput+0xb5/0x128
Dec 28 19:33:17 brouette kernel:  [<c015cb0d>] __link_path_walk+0x84a/0xc5b
Dec 28 19:33:17 brouette kernel:  [<c0167c2f>] mntput_no_expire+0x13/0x61
Dec 28 19:33:17 brouette kernel:  [<c015cf83>] link_path_walk+0x65/0xbc
Dec 28 19:33:17 brouette kernel:  [<c012d84a>] hrtimer_cancel+0xe/0x15
Dec 28 19:33:17 brouette kernel:  [<c012d959>] hrtimer_nanosleep+0x3d/0xf1
Dec 28 19:33:17 brouette kernel:  [<c0153623>] get_unused_fd+0x50/0xb5
Dec 28 19:33:17 brouette kernel:  [<c022b4c5>] kobject_get+0xf/0x13
Dec 28 19:33:17 brouette kernel:  [<c0225d22>] get_disk+0x32/0x4d
Dec 28 19:33:17 brouette kernel:  [<c0225d44>] exact_lock+0x7/0xd
Dec 28 19:33:17 brouette kernel:  [<c0284c82>] kobj_lookup+0x10d/0x117
Dec 28 19:33:17 brouette kernel:  [<c029aec0>] idecd_open+0x54/0xaa
Dec 28 19:33:17 brouette kernel:  [<c0175b37>] blkdev_open+0x0/0x53
Dec 28 19:33:17 brouette kernel:  [<c0175798>] do_open+0x7b/0x28d
Dec 28 19:33:17 brouette kernel:  [<c015bf10>] may_open+0x4d/0x1cd
Dec 28 19:33:17 brouette kernel:  [<c0175b37>] blkdev_open+0x0/0x53
Dec 28 19:33:17 brouette kernel:  [<c0175b5c>] blkdev_open+0x25/0x53
Dec 28 19:33:17 brouette kernel:  [<c0153737>] __dentry_open+0xaf/0x19d
Dec 28 19:33:17 brouette kernel:  [<c01538b2>] nameidata_to_filp+0x31/0x3a
Dec 28 19:33:17 brouette kernel:  [<c01538f4>] do_filp_open+0x39/0x40
Dec 28 19:33:17 brouette kernel:  [<c012d84a>] hrtimer_cancel+0xe/0x15
Dec 28 19:33:17 brouette kernel:  [<c012d959>] hrtimer_nanosleep+0x3d/0xf1
Dec 28 19:33:17 brouette kernel:  [<c0153623>] get_unused_fd+0x50/0xb5
Dec 28 19:33:17 brouette kernel:  [<c0153939>] do_sys_open+0x3e/0xc7
Dec 28 19:33:17 brouette kernel:  [<c01539fd>] sys_open+0x1c/0x20
Dec 28 19:33:17 brouette kernel:  [<c0102c5c>] syscall_call+0x7/0xb
Dec 28 19:33:17 brouette kernel:  =======================


Dec 28 19:56:18 brouette kernel: BUG: scheduling while atomic: emacs-snapshot/0x20000000/2093
Dec 28 19:56:18 brouette kernel:  [<c0380635>] __sched_text_start+0x615/0xafb
Dec 28 19:56:18 brouette kernel:  [<c0224052>] blk_done_softirq+0x51/0x5e
Dec 28 19:56:18 brouette kernel:  [<c011e115>] __do_softirq+0x71/0xd6
Dec 28 19:56:18 brouette kernel:  [<c0105293>] do_IRQ+0x45/0x82
Dec 28 19:56:18 brouette kernel:  [<c024753f>] soft_cursor+0x147/0x1a8
Dec 28 19:56:18 brouette kernel:  [<c01035f7>] common_interrupt+0x23/0x28
Dec 28 19:56:18 brouette kernel:  [<c011527f>] __cond_resched+0x16/0x34
Dec 28 19:56:18 brouette kernel:  [<c0380b3e>] cond_resched+0x23/0x2a
Dec 28 19:56:18 brouette kernel:  [<c03822ee>] __reacquire_kernel_lock+0x1c/0x3c
Dec 28 19:56:18 brouette kernel:  [<c038065d>] __sched_text_start+0x63d/0xafb
Dec 28 19:56:18 brouette kernel:  [<c011e101>] __do_softirq+0x5d/0xd6
Dec 28 19:56:18 brouette kernel:  [<c02412f8>] fbcon_putcs+0x188/0x2b2
Dec 28 19:56:18 brouette kernel:  [<c0246764>] bit_putcs+0x0/0x62e
Dec 28 19:56:18 brouette kernel:  [<c011527f>] __cond_resched+0x16/0x34
Dec 28 19:56:18 brouette kernel:  [<c0380b3e>] cond_resched+0x23/0x2a
Dec 28 19:56:18 brouette kernel:  [<c0242698>] fbcon_redraw+0x68/0x189
Dec 28 19:56:18 brouette kernel:  [<c0244883>] fbcon_scroll+0x1b2/0xe8f
Dec 28 19:56:18 brouette kernel:  [<c027a7f2>] scrup+0xc3/0xcd
Dec 28 19:56:18 brouette kernel:  [<c027a83b>] lf+0x3f/0x4b
Dec 28 19:56:18 brouette kernel:  [<c027cc07>] do_con_write+0x543/0x1762
Dec 28 19:56:18 brouette kernel:  [<c013d8dc>] __alloc_pages+0x4f/0x2f8
Dec 28 19:56:18 brouette kernel:  [<c0139027>] __lock_page+0x59/0x60
Dec 28 19:56:18 brouette kernel:  [<c0241ad5>] fbcon_cursor+0x17f/0x2af
Dec 28 19:56:18 brouette kernel:  [<c0246d92>] bit_cursor+0x0/0x596
Dec 28 19:56:18 brouette kernel:  [<c0119d64>] release_console_sem+0x1bd/0x20d
Dec 28 19:56:18 brouette kernel:  [<c027de5b>] con_write+0x9/0x17
Dec 28 19:56:18 brouette kernel:  [<c02724ad>] write_chan+0x18e/0x310
Dec 28 19:56:18 brouette kernel:  [<c0115242>] default_wake_function+0x0/0xc
Dec 28 19:56:18 brouette kernel:  [<c026fe23>] tty_write+0x119/0x1cd
Dec 28 19:56:18 brouette kernel:  [<c027231f>] write_chan+0x0/0x310
Dec 28 19:56:18 brouette kernel:  [<c0155253>] vfs_write+0x8b/0x142
Dec 28 19:56:18 brouette kernel:  [<c026fd0a>] tty_write+0x0/0x1cd
Dec 28 19:56:18 brouette kernel:  [<c0155898>] sys_write+0x41/0x6a
Dec 28 19:56:18 brouette kernel:  [<c0102c5c>] syscall_call+0x7/0xb
Dec 28 19:56:18 brouette kernel:  =======================


Attached : dmesg and config.

-- 
Damien Wyart