Message-ID: <20170717181439.GB11283@westernst>
Date:   Mon, 17 Jul 2017 19:14:40 +0100
From:   Piotr Gregor <piotrgregor@...ncme.org>
To:     Ian Abbott <abbotti@....co.uk>
Cc:     linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        sebastian.siewior@...utronix.de, tglx@...utronix.de,
        gregkh@...uxfoundation.org, devel@...verdev.osuosl.org
Subject: Re: [BUG] drivers: staging: comedi: do not call blocking ops when
 !TASK_RUNNING; state=1

Hi Ian,

I am afraid I have more problems with running Comedi on rt-patched kernel than
only that. I am still trying to figure out the specific reason - hopefully it is
my fault and I scrued up my own code, but so far it seems pcie215
support doesn't work at least in the same way on rt-patched kernel
as it was on non-rt. I will dig it a little bit harder, likely coming with another
bug reports shoud they be observed.

Do you know about other experience other people may have using Comedi
for pcie215 on rt-patched kernels, specifically 4.4.70?

Has Comedi been tested on rt kernels by yourself?

cheers,
Piotr

On Mon, Jul 17, 2017 at 05:02:45PM +0100, Ian Abbott wrote:
> On 17/07/17 15:48, Piotr Gregor wrote:
> >Calling blocking operations from wrong context.
> >Kernel:
> >
> >Linux piotrpc 4.4.70-rt83 #1 SMP PREEMPT RT Thu Jul 13 08:42:02 BST 2017 x86_64 GNU/Linux
> >
> >[   80.542018] NOHZ: local_softirq_pending 80
> >[  125.175471] ------------[ cut here ]------------
> >[  125.175491] WARNING: CPU: 0 PID: 1497 at kernel/sched/core.c:7833 __might_sleep+0x9f/0xb0()
> >[  125.175728] do not call blocking ops when !TASK_RUNNING; state=1 set at [<ffffffffc0575741>] comedi_read+0x1a1/0x610 [comedi]
> >[  125.175735] Modules linked in: cpufreq_conservative cpufreq_powersave cpufreq_userspace cfg80211 nfsd auth_rpcgss oid_registry nfs_acl nfs lockd grace fscache sunrpc nls_ascii nls_cp437 vfat fat snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic intel_rapl joydev intel_powerclamp coretemp kvm drbg efi_pstore ansi_cprng irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd i915 serio_raw pcspkr efivars snd_hda_intel amplc_dio200_pci(C) amplc_dio200_common(C) snd_hda_codec iTCO_wdt comedi_8254(C) comedi_pci(C) iTCO_vendor_support comedi(C) snd_hda_core snd_hwdep snd_pcm drm_kms_helper snd_timer drm snd mei_me soundcore mei i2c_algo_bit shpchp eeepc_wmi asus_wmi sparse_keymap mxm_wmi battery hci_uart btbcm btqca btintel
> >[  125.175824]  bluetooth
> >[  125.175825]  wmi
> >[  125.175826]  rfkill
> >[  125.175827]  video
> >[  125.175828]  intel_lpss_acpi
> >[  125.175830]  intel_lpss
> >[  125.175831]  evdev
> >[  125.175832]  mfd_core
> >[  125.175833]  acpi_als
> >[  125.175834]  acpi_pad
> >[  125.175835]  kfifo_buf
> >[  125.175836]  button
> >[  125.175838]  industrialio
> >[  125.175839]  fuse
> >[  125.175840]  parport_pc
> >[  125.175841]  ppdev
> >[  125.175842]  lp
> >[  125.175843]  parport
> >[  125.175844]  autofs4
> >[  125.175845]  ext4
> >[  125.175846]  crc16
> >[  125.175847]  mbcache
> >[  125.175848]  jbd2
> >[  125.175849]  hid_generic
> >[  125.175851]  usbhid
> >[  125.175852]  sg
> >[  125.175853]  sr_mod
> >[  125.175854]  cdrom
> >[  125.175855]  sd_mod
> >[  125.175856]  crc32c_intel
> >[  125.175857]  ahci
> >[  125.175858]  libahci
> >[  125.175859]  psmouse
> >[  125.175860]  xhci_pci
> >[  125.175861]  libata
> >[  125.175862]  r8169
> >[  125.175864]  i2c_i801
> >[  125.175865]  mii
> >[  125.175866]  xhci_hcd
> >[  125.175867]  tg3
> >[  125.175868]  ptp
> >[  125.175869]  scsi_mod
> >[  125.175870]  usbcore
> >[  125.175871]  pps_core
> >[  125.175872]  libphy
> >[  125.175873]  usb_common
> >[  125.175874]  fan
> >[  125.175875]  thermal
> >[  125.175876]  i2c_hid
> >[  125.175877]  hid
> >[  125.175878]  fjes
> >
> >[  125.175926] CPU: 0 PID: 1497 Comm: txrx Tainted: G        WC      4.4.70-rt83 #1
> >[  125.175928] Hardware name: NOVATECH LTD PC-XB04472/H110M-C, BIOS 3019 01/06/2017
> >[  125.175935]  0000000000000000 ffff8802205b3cb0 ffffffff81387160 ffff8802205b3cf8
> >[  125.175940]  0000000000000009 ffff8802205b3ce8 ffffffff81089766 ffffffffc057ca60
> >[  125.175944]  00000000000002dc 0000000000000000 0000000000000001 0000000000000001
> >[  125.175945] Call Trace:
> >[  125.175955]  [<ffffffff81387160>] dump_stack+0x85/0xc5
> >[  125.175963]  [<ffffffff81089766>] warn_slowpath_common+0x86/0xe0
> >[  125.175971]  [<ffffffff8108980c>] warn_slowpath_fmt+0x4c/0x50
> >[  125.175980]  [<ffffffff81185577>] ? trace_preempt_on+0x1a7/0x2b0
> >[  125.175985]  [<ffffffff8168ca95>] ? schedule+0x55/0xe0
> >[  125.175994]  [<ffffffffc0575741>] ? comedi_read+0x1a1/0x610 [comedi]
> >[  125.176001]  [<ffffffffc0575741>] ? comedi_read+0x1a1/0x610 [comedi]
> >[  125.176005]  [<ffffffff810b6d0f>] __might_sleep+0x9f/0xb0
> >[  125.176012]  [<ffffffff811f54cb>] __might_fault+0x3b/0xb0
> >[  125.176020]  [<ffffffffc057597f>] comedi_read+0x3df/0x610 [comedi]
> >[  125.176034]  [<ffffffff810bebf0>] ? wake_up_process+0x20/0x20
> >[  125.176044]  [<ffffffff812406d8>] __vfs_read+0x28/0xe0
> >[  125.176053]  [<ffffffff812f1f06>] ? security_file_permission+0xa6/0xc0
> >[  125.176060]  [<ffffffff81240c53>] ? rw_verify_area+0x53/0xf0
> >[  125.176066]  [<ffffffff81240d79>] vfs_read+0x89/0x130
> >[  125.176074]  [<ffffffff81241b79>] SyS_read+0x49/0xb0
> >[  125.176084]  [<ffffffff81691876>] entry_SYSCALL_64_fastpath+0x16/0x7a
> >[  125.176095] ---[ end trace 0000000000000003 ]---
> >
> >
> >cheers,
> >Piotr
> 
> Thanks for the bug report.  I think comedi_read() in
> "drivers/staging/comedi/comedi_fops.c" needs a call to
> set_current_state(TASK_RUNNING) just before the call to copy_to_user(...).
> 
> Similarly, comedi_write() needs a call to set_current_task(TASK_RUNNING)
> just before the call to copy_from_user(...), and another call to
> set_current_task(TASK_RUNNING) before the call to mutex_lock().
> 
> I'll work on a patch.
> 
> -- 
> -=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@....co.uk> )=-
> -=(                          Web: http://www.mev.co.uk/  )=-

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