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February 2022

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22 discussions

Linux driver of vt6656 from staging area causes system to freeze.
by Philipp Hortmann Feb. 3, 2022

Feb. 3, 2022

I managed to get a device vt6656 (USB WiFi adapter). The device works OK when the computer is started and driver loaded. When the WLAN is disabled the system freezes often. I am using ubuntu 20.04 with kernel 5.17.0-rc1 x86_64 branch: staging-testing After some tries I found out that it is a function in vnt_stop() main_usb.c with the following line that is causing this. usb_kill_urb(priv→interrupt_urb); But this memory is after this line still in use. Digging deeper I found that the usb_submit_urb() function (in usbpipe.c vnt_start_interrupt_urb_complete) is called after the usb_kill_urb() is executed. So I tied the execution of the usb_submit_urb() to a flag called DEVICE_FLAGS_DISCONNECTED. After that no crashes were observed. So here my questions: - Is this the right place to fix? - Do I need to log a bug report before a patch? Here a patch proposal: From d403ed1a1c2483a3a8b44e96c12edbfa2a53d356 Mon Sep 17 00:00:00 2001 From: Philipp Hortmann <philipp.g.hortmann(a)gmail.com> Date: Wed, 2 Feb 2022 20:15:04 +0100 Subject: [PATCH] staging: vt6656: Fix crash when WLAN is turned off To: Forest Bond <forest(a)alittletooquiet.net>,Greg Kroah-Hartman <gregkh(a)linuxfoundation.org>,linux-staging@lists.linux.dev,linux-kernel@vger.kernel.org Stop submitting urbs before calling usb_kill_urb() and usb_free_urb(). Signed-off-by: Philipp Hortmann <philipp.g.hortmann(a)gmail.com> --- drivers/staging/vt6656/usbpipe.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/staging/vt6656/usbpipe.c b/drivers/staging/vt6656/usbpipe.c index 7f45734390f6..d505b4b69ba4 100644 --- a/drivers/staging/vt6656/usbpipe.c +++ b/drivers/staging/vt6656/usbpipe.c @@ -230,7 +230,9 @@ static void vnt_start_interrupt_urb_complete(struct urb *urb) else vnt_int_process_data(priv); - status = usb_submit_urb(priv->interrupt_urb, GFP_ATOMIC); + if (!test_bit(DEVICE_FLAGS_DISCONNECTED, &priv->flags)) + status = usb_submit_urb(priv->interrupt_urb, GFP_ATOMIC); + if (status) dev_dbg(&priv->usb->dev, "Submit int URB failed %d\n", status); } -- 2.25.1

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How to debug stuck read?
by Dāvis Mosāns Feb. 2, 2022

Feb. 2, 2022

Hi, I have a corrupted file on BTRFS which has CoW disabled thus no checksum. Trying to read this file causes the process to get stuck forever. It doesn't return EIO. How can I find out why it gets stuck? $ ddrescue -b 1 currupted_file /tmp/temp GNU ddrescue 1.26 Press Ctrl-C to interrupt ipos: 0 B, non-trimmed: 0 B, current rate: 0 B/s opos: 0 B, non-scraped: 0 B, average rate: 0 B/s non-tried: 8388 kB, bad-sector: 0 B, error rate: 0 B/s rescued: 0 B, bad areas: 0, run time: 0s pct rescued: 0.00%, read errors: 0, remaining time: n/a time since last successful read: n/a Copying non-tried blocks... Pass 1 (forwards) ^C // doesn't stop with Ctrl+C nor SIGTERM $ gdb -q -p 3449 Attaching to process 3449 ^C // same gets stuck $ cat /proc/3449/stack | ./scripts/decode_stacktrace.sh vmlinux folio_wait_bit_common (mm/filemap.c:1314) filemap_get_pages (mm/filemap.c:2622) filemap_read (mm/filemap.c:2676) new_sync_read (fs/read_write.c:401 (discriminator 1)) vfs_read (fs/read_write.c:481) ksys_read (fs/read_write.c:619) do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:113) I enabled CONFIG_BTRFS_DEBUG=y CONFIG_BTRFS_ASSERT=y CONFIG_LOCKDEP_SUPPORT=y CONFIG_LOCKDEP=y CONFIG_LOCKUP_DETECTOR=y CONFIG_SOFTLOCKUP_DETECTOR=y CONFIG_LOCK_DEBUGGING_SUPPORT=y CONFIG_PROVE_LOCKING=y CONFIG_DEBUG_SPINLOCK=y CONFIG_DEBUG_LOCK_ALLOC=y but in dmesg only thing that shows up is a lot of BTRFS error (device sdh): invalid lzo header, lzo len 2937060802 compressed len 4096 If I try to do btrfs send, it gets stuck same way $ btrfs send -v /mnt/fs > /dev/null $ cat /proc/4712/stack | ./scripts/decode_stacktrace.sh vmlinux folio_wait_bit_common (mm/filemap.c:1314) __filemap_get_folio (mm/filemap.c:1690 ./include/linux/pagemap.h:779 mm/filemap.c:1960) pagecache_get_page (mm/folio-compat.c:126) send_extent_data (fs/btrfs/send.c:4980 fs/btrfs/send.c:5048 fs/btrfs/send.c:5235) btrfs process_extent (fs/btrfs/send.c:5575 fs/btrfs/send.c:5959) btrfs btrfs_ioctl_send (fs/btrfs/send.c:6770 fs/btrfs/send.c:7368 fs/btrfs/send.c:7688) btrfs _btrfs_ioctl_send (fs/btrfs/ioctl.c:4963) btrfs btrfs_ioctl (fs/btrfs/ioctl.c:5072) btrfs __x64_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:874 fs/ioctl.c:860 fs/ioctl.c:860) do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:113) I'm now using 5.17.0-rc2 but it's exactly same with 5.16.5 Thanks! Best regards, Dāvis

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