mainlining shenanigans
7030082a74
When tearing down the n_gsm ldisc while one or more of its child ports are open, a lock dep warning occurs: [ 56.254258] ====================================================== [ 56.260447] WARNING: possible circular locking dependency detected [ 56.266641] 5.2.0-00118-g1fd58e20e5b0 #30 Not tainted [ 56.271701] ------------------------------------------------------ [ 56.277890] cmux/271 is trying to acquire lock: [ 56.282436] 8215283a (&tty->legacy_mutex){+.+.}, at: __tty_hangup.part.0+0x58/0x27c [ 56.290128] [ 56.290128] but task is already holding lock: [ 56.295970] e9e2b842 (&gsm->mutex){+.+.}, at: gsm_cleanup_mux+0x9c/0x15c [ 56.302699] [ 56.302699] which lock already depends on the new lock. [ 56.302699] [ 56.310884] [ 56.310884] the existing dependency chain (in reverse order) is: [ 56.318372] [ 56.318372] -> #2 (&gsm->mutex){+.+.}: [ 56.323624] mutex_lock_nested+0x1c/0x24 [ 56.328079] gsm_cleanup_mux+0x9c/0x15c [ 56.332448] gsmld_ioctl+0x418/0x4e8 [ 56.336554] tty_ioctl+0x96c/0xcb0 [ 56.340492] do_vfs_ioctl+0x41c/0xa5c [ 56.344685] ksys_ioctl+0x34/0x60 [ 56.348535] ret_fast_syscall+0x0/0x28 [ 56.352815] 0xbe97cc04 [ 56.355791] [ 56.355791] -> #1 (&tty->ldisc_sem){++++}: [ 56.361388] tty_ldisc_lock+0x50/0x74 [ 56.365581] tty_init_dev+0x88/0x1c4 [ 56.369687] tty_open+0x1c8/0x430 [ 56.373536] chrdev_open+0xa8/0x19c [ 56.377560] do_dentry_open+0x118/0x3c4 [ 56.381928] path_openat+0x2fc/0x1190 [ 56.386123] do_filp_open+0x68/0xd4 [ 56.390146] do_sys_open+0x164/0x220 [ 56.394257] kernel_init_freeable+0x328/0x3e4 [ 56.399146] kernel_init+0x8/0x110 [ 56.403078] ret_from_fork+0x14/0x20 [ 56.407183] 0x0 [ 56.409548] [ 56.409548] -> #0 (&tty->legacy_mutex){+.+.}: [ 56.415402] __mutex_lock+0x64/0x90c [ 56.419508] mutex_lock_nested+0x1c/0x24 [ 56.423961] __tty_hangup.part.0+0x58/0x27c [ 56.428676] gsm_cleanup_mux+0xe8/0x15c [ 56.433043] gsmld_close+0x48/0x90 [ 56.436979] tty_ldisc_kill+0x2c/0x6c [ 56.441173] tty_ldisc_release+0x88/0x194 [ 56.445715] tty_release_struct+0x14/0x44 [ 56.450254] tty_release+0x36c/0x43c [ 56.454365] __fput+0x94/0x1e8 Avoid the warning by doing the port hangup asynchronously. Signed-off-by: Martin Hundebøll <martin@geanix.com> Link: https://lore.kernel.org/r/20190822215601.9028-1-martin@geanix.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.