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From: Peter Feuerer on 1 Mar 2010 13:20
Hi Greg,

I tried to flash an AVR microcontroler via an USB to serial converter which
uses pl2302 driver. It didn't work, so I set up following test to reproduce
the bug:

I connected two pls2302 usb-serial converters to two different usb-ports
of my machine and connected them with a rs232-nullmodem cable to each
other.

Terminal1:
cat /dev/ttyUSB1

Terminal2:
while true; do echo 123456789012345678901234567890 > /dev/ttyUSB0 ; done


When both usb-serial converters are plugged in, the first few lines appear
correctly on Terminal1. Then I noticed two different bahaviors:

1) The lines on Terminal1 are corrupted like:
"1111111111111111111111123456789012345678901234567890"

2) The lines "123456789012345678901234567890" appear correctly on Terminal1
but when I kill the "cat" command and start it again, there's only one line
and then no output anymore.

I verified this behavior on two different machines running the same
kernel (version 2.6.32.9).

Additionally a calltrace is printed to dmesg (see end of mail)


I'm not 100% sure, but if I remember correctly was flashing AVR
microcontrollers with pl2302 possible about the time when kernel 2.6.22 was
released.

If you've got any questions I'd be pleased to help you.

best regards,
--peter;




---
[piie(a)deskpiie ~]$ lsusb
Bus 002 Device 013: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial
Port
Bus 002 Device 012: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial
Port




------------[ cut here ]------------
WARNING: at drivers/usb/serial/usb-serial.c:406 serial_write_room+0x74/0x80
[usbserial]()
Hardware name: To Be Filled By O.E.M.
Modules linked in: pl2303 usbserial sha256_generic aes_i586 aes_generic cbc
ipv6 snd_hda_codec_nvhdmi usbhid hid snd_hda_codec_via snd_seq_dummy
snd_seq_oss snd_seq_midi_event snd_seq snd_seq_device snd_pcm_oss
snd_mixer_oss snd_hda_intel snd_hda_codec snd_hwdep snd_pcm snd_timer
ohci_hcd snd soundcore coretemp snd_page_alloc nvidia(P) shpchp i2c_nforce2
ehci_hcd agpgart wmi psmouse thermal pci_hotplug i2c_core usbcore sg
forcedeth button processor serio_raw vboxdrv evdev dm_crypt dm_mod fuse
rtc_cmos rtc_core rtc_lib ext4 mbcache jbd2 crc16 sr_mod cdrom sd_mod
pata_acpi ahci ata_generic libata scsi_mod
Pid: 15, comm: events/0 Tainted: P W 2.6.32-ARCH #1
Call Trace:
[<c104042e>] ? warn_slowpath_common+0x6e/0xb0
[<f8c634b4>] ? serial_write_room+0x74/0x80 [usbserial]
[<c1040483>] ? warn_slowpath_null+0x13/0x20
[<f8c634b4>] ? serial_write_room+0x74/0x80 [usbserial]
[<c11ddf15>] ? tty_write_room+0x15/0x20
[<c11db6a7>] ? process_echoes+0x47/0x2b0
[<c11dda85>] ? n_tty_receive_buf+0xe45/0x10c0
[<c1002374>] ? __switch_to+0x184/0x190
[<c103655b>] ? finish_task_switch+0x3b/0xa0
[<c12b77d9>] ? schedule+0x2f9/0xa30
[<f8e2cfea>] ? usb_autopm_do_interface+0x7a/0xe0 [usbcore]
[<c11e023a>] ? flush_to_ldisc+0x14a/0x180
[<c11e00f0>] ? flush_to_ldisc+0x0/0x180
[<c1056f7f>] ? worker_thread+0x11f/0x260
[<c105adf0>] ? autoremove_wake_function+0x0/0x40
[<c1056e60>] ? worker_thread+0x0/0x260
[<c105ab44>] ? kthread+0x74/0x80
[<c105aad0>] ? kthread+0x0/0x80
[<c1004627>] ? kernel_thread_helper+0x7/0x10
---[ end trace 4162a861717078f5 ]---
------------[ cut here ]------------

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Prev: [tip:x86/mm] resource: Fix generic page_is_ram() for partial RAM pages
Next: Export per-tid and per-tgid cputime in nanoseconds.