Looks like there's some race contition in switching ldiscs on USB serial ports. The following warnings trigger sometimes after killing and restarting process that changes ldisc and waits forever. In case you want to look at the code, there it is: http://rere.qmqm.pl/~mirq/sermmc/ The connected USB device is an Actel IGLOO starter kit board with CP2102 usb-to-serial chip. $ lsusb|grep CP210 Bus 002 Device 004: ID 10c4:ea60 Cygnal Integrated Products, Inc. CP210x Composite Device Best Regards, Michał Mirosław Mar 11 03:25:41 rechot kernel: [ 715.018168] PM: Removing info for No Bus:mmc1 Mar 11 03:25:52 rechot kernel: [ 725.999013] ------------[ cut here ]------------ Mar 11 03:25:52 rechot kernel: [ 725.999078] WARNING: at drivers/usb/serial/usb-serial.c:376 serial_write_room+0x4f/0x63 [usbserial]() Mar 11 03:25:52 rechot kernel: [ 725.999127] Hardware name: hp compaq nx9500(PF031UA#ABA) Mar 11 03:25:52 rechot kernel: [ 725.999162] Modules linked in: sermmc crc7 sha256_generic nsc_ircc nfsd exportfs sit tunnel4 nfs lockd nfs_acl auth_rpcgss sunrpc tun ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 nf_conntrack_ipv6 nf_defrag_ipv4 xt_state iptable_filter ipt_addrtype ip6table_filter xt_dscp xt_string xt_owner xt_multiport xt_iprange xt_mark xt_conntrack xt_DSCP xt_connmark xt_NFQUEUE xt_MARK xt_CONNMARK nf_conntrack ip_tables irlan irnet ircomm_tty ip6_tables ircomm x_tables fuse snd_pcm_oss snd_mixer_oss snd_seq_dummy snd_seq_oss snd_seq_midi_event snd_seq snd_usb_audio snd_hwdep snd_usb_lib snd_rawmidi snd_seq_device aes_i586 aes_generic cfg80211 rfkill i2c_dev loop kqemu ppp_generic slhc cp210x usbserial usbhid nvidia(P) tulip snd_intel8x0 snd_intel8x0m snd_ac97_codec cb710_mmc mmc_core pcmcia ac97_bus snd_pcm firewire_ohci i2c_i801 irda sr_mod snd_timer snd firewire_core ehci_hcd cb710 i2c_core sg video uhci_hcd pcspkr ppdev backlight output parport_pc parport yenta_socket rsrc_nonstatic cdrom pcmcia_core intel_agp crc_ccitt agpgart joydev iTCO_wdt usbcore soundcore crc_itu_t snd_page_alloc [last unloaded: nsc_ircc] Mar 11 03:25:52 rechot kernel: [ 726.000575] Pid: 9, comm: events/0 Tainted: P A 2.6.33 #1 Mar 11 03:25:52 rechot kernel: [ 726.000578] Call Trace: Mar 11 03:25:52 rechot kernel: [ 726.000593] [<c013270a>] warn_slowpath_common+0x65/0x95 Mar 11 03:25:52 rechot kernel: [ 726.000600] [<c013274c>] warn_slowpath_null+0x12/0x15 Mar 11 03:25:52 rechot kernel: [ 726.000618] [<e1ad4643>] serial_write_room+0x4f/0x63 [usbserial] Mar 11 03:25:52 rechot kernel: [ 726.000629] [<c02a08e5>] tty_write_room+0x1d/0x1f Mar 11 03:25:52 rechot kernel: [ 726.000634] [<c029e5c8>] process_echoes+0x42/0x24b Mar 11 03:25:52 rechot kernel: [ 726.000641] [<c029e38b>] ? echo_char+0x74/0x79 Mar 11 03:25:52 rechot kernel: [ 726.000648] [<c029fb58>] n_tty_receive_buf+0x3c9/0xfcf Mar 11 03:25:52 rechot kernel: [ 726.000659] [<c03a79a9>] ? _raw_spin_unlock_irq+0x1f/0x2a Mar 11 03:25:52 rechot kernel: [ 726.000668] [<c012969d>] ? finish_task_switch+0x3f/0x6a Mar 11 03:25:52 rechot kernel: [ 726.000674] [<c0122e26>] ? need_resched+0x19/0x23 Mar 11 03:25:52 rechot kernel: [ 726.000682] [<c03a62f1>] ? schedule+0x7d3/0x7ff Mar 11 03:25:52 rechot kernel: [ 726.000692] [<c013dacd>] ? lock_timer_base+0x24/0x43 Mar 11 03:25:52 rechot kernel: [ 726.000700] [<c03a79d4>] ? _raw_spin_unlock_irqrestore+0x20/0x2b Mar 11 03:25:52 rechot kernel: [ 726.000707] [<c02a1a28>] ? tty_ldisc_try+0x3b/0x41 Mar 11 03:25:52 rechot kernel: [ 726.000714] [<c02a269c>] flush_to_ldisc+0xd4/0x168 Mar 11 03:25:52 rechot kernel: [ 726.000721] [<c0145481>] worker_thread+0x15f/0x1e8 Mar 11 03:25:52 rechot kernel: [ 726.000726] [<c02a25c8>] ? flush_to_ldisc+0x0/0x168 Mar 11 03:25:52 rechot kernel: [ 726.000737] [<c0148803>] ? autoremove_wake_function+0x0/0x38 Mar 11 03:25:52 rechot kernel: [ 726.000745] [<c0145322>] ? worker_thread+0x0/0x1e8 Mar 11 03:25:52 rechot kernel: [ 726.000751] [<c014843b>] kthread+0x66/0x6b Mar 11 03:25:52 rechot kernel: [ 726.000757] [<c01483d5>] ? kthread+0x0/0x6b Mar 11 03:25:52 rechot kernel: [ 726.000767] [<c0102e36>] kernel_thread_helper+0x6/0x10 Mar 11 03:25:52 rechot kernel: [ 726.000775] ---[ end trace f9f795998259dd46 ]--- Mar 11 03:25:52 rechot kernel: [ 726.000779] ------------[ cut here ]------------ Mar 11 03:25:52 rechot kernel: [ 726.000790] WARNING: at drivers/usb/serial/usb-serial.c:363 serial_write+0x69/0x8a [usbserial]() Mar 11 03:25:52 rechot kernel: [ 726.000798] Hardware name: hp compaq nx9500(PF031UA#ABA) Mar 11 03:25:52 rechot kernel: [ 726.000800] Modules linked in: sermmc crc7 sha256_generic nsc_ircc nfsd exportfs sit tunnel4 nfs lockd nfs_acl auth_rpcgss sunrpc tun ipt_MASQUERADE iptable_nat nf_nat nf_conntrack_ipv4 nf_conntrack_ipv6 nf_defrag_ipv4 xt_state iptable_filter ipt_addrtype ip6table_filter xt_dscp xt_string xt_owner xt_multiport xt_iprange xt_mark xt_conntrack xt_DSCP xt_connmark xt_NFQUEUE xt_MARK xt_CONNMARK nf_conntrack ip_tables irlan irnet ircomm_tty ip6_tables ircomm x_tables fuse snd_pcm_oss snd_mixer_oss snd_seq_dummy snd_seq_oss snd_seq_midi_event snd_seq snd_usb_audio snd_hwdep snd_usb_lib snd_rawmidi snd_seq_device aes_i586 aes_generic cfg80211 rfkill i2c_dev loop kqemu ppp_generic slhc cp210x usbserial usbhid nvidia(P) tulip snd_intel8x0 snd_intel8x0m snd_ac97_codec cb710_mmc mmc_core pcmcia ac97_bus snd_pcm firewire_ohci i2c_i801 irda sr_mod snd_timer snd firewire_core ehci_hcd cb710 i2c_core sg video uhci_hcd pcspkr ppdev backlight output parport_pc parport yenta_socket rsrc_nonstatic cdrom pcmcia_core intel_agp crc_ccitt agpgart joydev iTCO_wdt usbcore soundcore crc_itu_t snd_page_alloc [last unloaded: nsc_ircc] Mar 11 03:25:52 rechot kernel: [ 726.000924] Pid: 9, comm: events/0 Tainted: P AW 2.6.33 #1 Mar 11 03:25:52 rechot kernel: [ 726.000928] Call Trace: Mar 11 03:25:52 rechot kernel: [ 726.000939] [<c013270a>] warn_slowpath_common+0x65/0x95 Mar 11 03:25:52 rechot kernel: [ 726.000950] [<c013274c>] warn_slowpath_null+0x12/0x15 Mar 11 03:25:52 rechot kernel: [ 726.000963] [<e1ad46c0>] serial_write+0x69/0x8a [usbserial] Mar 11 03:25:52 rechot kernel: [ 726.000979] [<c029b122>] tty_put_char+0x2b/0x2f Mar 11 03:25:52 rechot kernel: [ 726.000985] [<c029e528>] do_output_char+0x198/0x1b2 Mar 11 03:25:52 rechot kernel: [ 726.000991] [<c029e72d>] process_echoes+0x1a7/0x24b Mar 11 03:25:52 rechot kernel: [ 726.000997] [<c029e38b>] ? echo_char+0x74/0x79 Mar 11 03:25:52 rechot kernel: [ 726.001028] [<c029fb58>] n_tty_receive_buf+0x3c9/0xfcf Mar 11 03:25:52 rechot kernel: [ 726.001041] [<c03a79a9>] ? _raw_spin_unlock_irq+0x1f/0x2a Mar 11 03:25:52 rechot kernel: [ 726.001046] [<c012969d>] ? finish_task_switch+0x3f/0x6a Mar 11 03:25:52 rechot kernel: [ 726.001053] [<c0122e26>] ? need_resched+0x19/0x23 Mar 11 03:25:52 rechot kernel: [ 726.001060] [<c03a62f1>] ? schedule+0x7d3/0x7ff Mar 11 03:25:52 rechot kernel: [ 726.001067] [<c013dacd>] ? lock_timer_base+0x24/0x43 Mar 11 03:25:52 rechot kernel: [ 726.001079] [<c03a79d4>] ? _raw_spin_unlock_irqrestore+0x20/0x2b Mar 11 03:25:52 rechot kernel: [ 726.001084] [<c02a1a28>] ? tty_ldisc_try+0x3b/0x41 Mar 11 03:25:52 rechot kernel: [ 726.001092] [<c02a269c>] flush_to_ldisc+0xd4/0x168 Mar 11 03:25:52 rechot kernel: [ 726.001098] [<c0145481>] worker_thread+0x15f/0x1e8 Mar 11 03:25:52 rechot kernel: [ 726.001108] [<c02a25c8>] ? flush_to_ldisc+0x0/0x168 Mar 11 03:25:52 rechot kernel: [ 726.001114] [<c0148803>] ? autoremove_wake_function+0x0/0x38 Mar 11 03:25:52 rechot kernel: [ 726.001122] [<c0145322>] ? worker_thread+0x0/0x1e8 Mar 11 03:25:52 rechot kernel: [ 726.001130] [<c014843b>] kthread+0x66/0x6b Mar 11 03:25:52 rechot kernel: [ 726.001136] [<c01483d5>] ? kthread+0x0/0x6b Mar 11 03:25:52 rechot kernel: [ 726.001146] [<c0102e36>] kernel_thread_helper+0x6/0x10 Mar 11 03:25:52 rechot kernel: [ 726.001150] ---[ end trace f9f795998259dd47 ]--- Mar 11 03:25:52 rechot kernel: [ 726.003363] PM: Adding info for No Bus:mmc1 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
