Re: [BUG v3.6.2, 3.7-rc1] Unable to rmmod any hid special driver

On Thu, Nov 1, 2012 at 11:43 AM, Jiri Kosina [off-list ref] wrote:

On Thu, 1 Nov 2012, Benjamin Tissoires wrote:

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hidraw_disconnect, thus, the hidraw device is still there, but the
input one not. It leads to the fact that the device is not working
anymore even if you call modprobe.

Any idea to solve that?

Guys, how about this?

I tested it against hid-multitouch and hid-logitech-dj and it's
working smoothly, thanks!

Thanks for testing.

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 drivers/hid/hidraw.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hidraw.c b/drivers/hid/hidraw.c
index 17d15bb..fce4256 100644
--- a/drivers/hid/hidraw.c
+++ b/drivers/hid/hidraw.c

@@ -560,10 +560,11 @@ static void drop_ref(struct hidraw *hidraw, int exists_bit)
 {
      mutex_lock(&minors_lock);
      if (exists_bit) {
-             hid_hw_close(hidraw->hid);
              hidraw->exist = 0;
-             if (hidraw->open)
+             if (hidraw->open) {
+                     hid_hw_close(hidraw->hid);
                      wake_up_interruptible(&hidraw->wait);
+             }
      } else {
              --hidraw->open;
      }

So this seems to fix the problem with rmmod/modprobe, but the patch has
apparently other problems. rmmoding special driver while reading from
hidraw interface causes this:

 ------------[ cut here ]------------
 WARNING: at lib/list_debug.c:59 __list_del_entry+0xa4/0xd0()
 Hardware name: 7470BN2
 list_del corruption. prev->next should be ffff880036f97178, but was 6b6b6b6b6b6b6b6b
 Modules linked in: af_packet rfcomm bnep tun iptable_mangle xt_DSCP nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables xt
e nf_conntrack iptable_filter ip_tables x_tables cpufreq_conservative cpufreq_userspace cpufreq_powersave acpi_cpufreq mperf dm_mod
m_intel kvm iwldvm mac80211 snd_hda_codec_conexant microcode usbhid sg iwlwifi pcspkr snd_hda_intel cfg80211 lpc_ich i2c_i801 mfd_c
imer snd_page_alloc thinkpad_acpi rfkill wmi snd ac soundcore battery tpm_tis tpm tpm_bios autofs4 uhci_hcd ehci_hcd usbcore usb_co
button edd fan processor ata_generic thermal thermal_sys [last unloaded: hid_cypress]
 Pid: 4725, comm: hexdump Not tainted 3.7.0-rc3-00008-g35fd3dc #157
 Call Trace:
  [<ffffffff812f95c4>] ? __list_del_entry+0xa4/0xd0
  [<ffffffff812f95c4>] ? __list_del_entry+0xa4/0xd0
  [<ffffffff810452fa>] warn_slowpath_common+0x7a/0xb0
  [<ffffffff810453d1>] warn_slowpath_fmt+0x41/0x50
  [<ffffffff812f95c4>] __list_del_entry+0xa4/0xd0
  [<ffffffff812f9601>] list_del+0x11/0x40
  [<ffffffff81454a23>] hidraw_release+0x33/0x50
  [<ffffffff8118cd0a>] __fput+0xca/0x2b0
  [<ffffffff8118cf49>] ____fput+0x9/0x10
  [<ffffffff8106b7a1>] task_work_run+0xb1/0xe0
  [<ffffffff8104c81e>] do_exit+0x1ee/0x4c0
  [<ffffffff810adcad>] ? trace_hardirqs_on_caller+0x12d/0x1b0
  [<ffffffff8104cb37>] do_group_exit+0x47/0xc0
  [<ffffffff8104cbc2>] sys_exit_group+0x12/0x20
  [<ffffffff8158a529>] system_call_fastpath+0x16/0x1b
 ---[ end trace 3bec13493e086171 ]---

This is weird, on my setup (kernel 3.6.2 + Henrik's patches + Ratan's
patch + your fix), I don't have this warning.

My reproduction scenario was

- run hexdump on hidraw device driven by a special driver (hid-cypress in
  this case)
- let the device produce a few events
- rmmod hid-cypress while hexdump is still running

well, with the very same test (except I'm testing against
hid-multitouch), the warning doesn't show up on my configuration...

This triggers the warning immediately. Do you have list debugging truned
on in your .config?

I think so:

CONFIG_DEBUG_LIST=y

and here is the debug section:


CONFIG_SCHED_DEBUG=y
CONFIG_SCHEDSTATS=y
CONFIG_TIMER_STATS=y
# CONFIG_DEBUG_OBJECTS is not set
# CONFIG_SLUB_DEBUG_ON is not set
# CONFIG_SLUB_STATS is not set
# CONFIG_DEBUG_KMEMLEAK is not set
# CONFIG_DEBUG_RT_MUTEXES is not set
# CONFIG_RT_MUTEX_TESTER is not set
# CONFIG_DEBUG_SPINLOCK is not set
# CONFIG_DEBUG_MUTEXES is not set
# CONFIG_DEBUG_LOCK_ALLOC is not set
# CONFIG_PROVE_LOCKING is not set
CONFIG_SPARSE_RCU_POINTER=y
# CONFIG_LOCK_STAT is not set
# CONFIG_DEBUG_ATOMIC_SLEEP is not set
# CONFIG_DEBUG_LOCKING_API_SELFTESTS is not set
CONFIG_STACKTRACE=y
# CONFIG_DEBUG_STACK_USAGE is not set
# CONFIG_DEBUG_KOBJECT is not set
CONFIG_DEBUG_BUGVERBOSE=y
CONFIG_DEBUG_INFO=y
# CONFIG_DEBUG_INFO_REDUCED is not set
CONFIG_DEBUG_VM=y
# CONFIG_DEBUG_VIRTUAL is not set
# CONFIG_DEBUG_WRITECOUNT is not set
CONFIG_DEBUG_MEMORY_INIT=y
CONFIG_DEBUG_LIST=y
# CONFIG_TEST_LIST_SORT is not set
# CONFIG_DEBUG_SG is not set
# CONFIG_DEBUG_NOTIFIERS is not set
# CONFIG_DEBUG_CREDENTIALS is not set

Cheers,
Benjamin