On Mon, Aug 17, 2009 at 10:10 AM, Greg KH <greg@xxxxxxxxx> wrote:
On Thu, Aug 13, 2009 at 12:57:49PM -0700, srinivasramana wrote:
>
> Hi All,
>
> 1. I am using the tiny tty driver written by Greg long back. Looks like its
> too old and hence some compilation issues. Once i resolve that, its giving
> BUG on add_timer(i tried in 2.6.28 & 2.6.30).
> 2. I have two applications one reads and one which calls an ioctl on the
> same device node. the read app blocks once i start. In the ioctl from second
> app, i am using tty_flip_buffer_push() to write data to tty core so that the
> first app unblocks.
> But i am surprised to see that the data is written back to the tty device
> using write call.
>
> can anybody help me on this? How do i have first read app get the data?
Can you post the driver that you now have, and the error you are
getting?
thanks,
greg k-h
Hi Greg,
The error which i was getting is pasted below. I could see that this is getting resolved if i do init_timer in tiny_open() call before calling add_timer(). So that resolves this crash. But i still could see the application which is reading on this fd getting unblocked. After further debugging of tty, i found that at the place it wakes ou the waiting threads, its check for ICANON flag. when i un set this flag, my app got unblocked.
I am not sure what is this flag for? and why my app got unblocked now.
request help.
Error without init_timer() call:
------------[ cut here ]------------
[ 2980.134486] kernel BUG at include/linux/timer.h:165!
[ 2980.134490] invalid opcode: 0000 [#1] SMP
[ 2980.134492] Modules linked in: tinyyy_tty tiny_serial af_packet i915 drm binfmt_misc rfcomm sco bridge stp bnep l2cap bluetooth ppdev ipv6 acpi_cpufreq cpufreq_userspace cpufreq_conservative cpufreq_ondemand cpufreq_stats freq_table cpufreq_powersave wmi sbs pci_slot container video output sbshc battery iptable_filter ip_tables x_tables ac sbp2 parport_pc lp parport snd_hda_intel snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy psmouse snd_seq_oss serio_raw joydev evdev pcspkr iTCO_wdt iTCO_vendor_support snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq snd_timer snd_seq_device intel_agp button shpchp snd soundcore pci_hotplug snd_page_alloc agpgart heci ext3 jbd mbcache sr_mod cdrom sd_mod crc_t10dif sg pata_acpi usbhid hid pata_marvell ata_piix ata_generic ohci1394 ieee1394 libata scsi_mod dock ehci_hcd uhci_hcd usbcore e1000e thermal processor fan fbcon tileblit font bitblit softcursor fuse [last unloaded: tinyyy_tty]
[ 2980.134571]
[ 2980.134574] Pid: 7089, comm: tty_write Not tainted (2.6.27-7-generic #1)
[ 2980.134576] EIP: 0060:[<f90d79d0>] EFLAGS: 00210286 CPU: 0
[ 2980.134581] EIP is at tiny_open+0x130/0x160 [tinyyy_tty]
[ 2980.134583] EAX: ed37a980 EBX: ed35d300 ECX: ffffffff EDX: ed37a900
[ 2980.134586] ESI: ed11c800 EDI: 00000000 EBP: ed373e24 ESP: ed373e0c
[ 2980.134588] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
[ 2980.134591] Process tty_write (pid: 7089, ti=ed372000 task=ed333240 task.ti=ed372000)
[ 2980.134593] Stack: f90d7f68 00000000 ed35d308 f90d78a0 10400000 ed35d180 ed373e48 c02a343c
[ 2980.134600] 00000000 00025e2c 00000000 ed11c800 ed314ca0 ed35d180 00000000 ed373e58
[ 2980.134607] c02a3644 00000000 ed35d484 ed373e80 c01b4d95 ed35d180 ed314ca0 ed35d484
[ 2980.134614] Call Trace:
[ 2980.134618] [<f90d78a0>] ? tiny_open+0x0/0x160 [tinyyy_tty]
[ 2980.134623] [<c02a343c>] ? __tty_open+0x15c/0x340
[ 2980.134629] [<c02a3644>] ? tty_open+0x24/0x40
[ 2980.134633] [<c01b4d95>] ? chrdev_open+0xd5/0x1b0
[ 2980.134639] [<c01b01fc>] ? __dentry_open+0xbc/0x260
[ 2980.134643] [<c01b0477>] ? nameidata_to_filp+0x47/0x60
[ 2980.134647] [<c01b4cc0>] ? chrdev_open+0x0/0x1b0
[ 2980.134651] [<c01bdb1d>] ? do_filp_open+0x1bd/0x790
[ 2980.134655] [<c01e207c>] ? inotify_inode_queue_event+0xbc/0xe0
[ 2980.134660] [<c01e1fce>] ? inotify_inode_queue_event+0xe/0xe0
[ 2980.134664] [<c037e61d>] ? _spin_lock+0xd/0x10
[ 2980.134668] [<c01b3526>] ? __fput+0x146/0x190
[ 2980.134672] [<c01c9619>] ? expand_files+0x9/0x60
[ 2980.134676] [<c01c9750>] ? alloc_fd+0xe0/0x100
[ 2980.134680] [<c01afff5>] ? do_sys_open+0x65/0x100
[ 2980.134684] [<c01b00fe>] ? sys_open+0x2e/0x40
[ 2980.134687] [<c0103f7b>] ? sysenter_do_call+0x12/0x2f
[ 2980.134692] [<c0370000>] ? default_device_exit+0x70/0xb0
[ 2980.134696] =======================
Thanks & Regards,
-- Srinivas R
