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2989360d9c
Lockdep is reporting a possible circular locking dependency: ====================================================== WARNING: possible circular locking dependency detected 4.18.0-rc1-test-test+ #4 Not tainted ------------------------------------------------------ user_example/766 is trying to acquire lock: 0000000073479a0f (rdtgroup_mutex){+.+.}, at: pseudo_lock_dev_mmap but task is already holding lock: 000000001ef7a35b (&mm->mmap_sem){++++}, at: vm_mmap_pgoff+0x9f/0x which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&mm->mmap_sem){++++}: _copy_to_user+0x1e/0x70 filldir+0x91/0x100 dcache_readdir+0x54/0x160 iterate_dir+0x142/0x190 __x64_sys_getdents+0xb9/0x170 do_syscall_64+0x86/0x200 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&sb->s_type->i_mutex_key#3){++++}: start_creating+0x60/0x100 debugfs_create_dir+0xc/0xc0 rdtgroup_pseudo_lock_create+0x217/0x4d0 rdtgroup_schemata_write+0x313/0x3d0 kernfs_fop_write+0xf0/0x1a0 __vfs_write+0x36/0x190 vfs_write+0xb7/0x190 ksys_write+0x52/0xc0 do_syscall_64+0x86/0x200 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (rdtgroup_mutex){+.+.}: __mutex_lock+0x80/0x9b0 pseudo_lock_dev_mmap+0x2f/0x170 mmap_region+0x3d6/0x610 do_mmap+0x387/0x580 vm_mmap_pgoff+0xcf/0x110 ksys_mmap_pgoff+0x170/0x1f0 do_syscall_64+0x86/0x200 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: rdtgroup_mutex --> &sb->s_type->i_mutex_key#3 --> &mm->mmap_sem Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&mm->mmap_sem); lock(&sb->s_type->i_mutex_key#3); lock(&mm->mmap_sem); lock(rdtgroup_mutex); *** DEADLOCK *** 1 lock held by user_example/766: #0: 000000001ef7a35b (&mm->mmap_sem){++++}, at: vm_mmap_pgoff+0x9f/0x110 rdtgroup_mutex is already being released temporarily during pseudo-lock region creation to prevent the potential deadlock between rdtgroup_mutex and mm->mmap_sem that is obtained during device_create(). Move the debugfs creation into this area to avoid the same circular dependency. Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: fenghua.yu@intel.com Cc: tony.luck@intel.com Cc: vikas.shivappa@linux.intel.com Cc: gavin.hindman@intel.com Cc: jithu.joseph@intel.com Cc: hpa@zytor.com Link: https://lkml.kernel.org/r/fffb57f9c6b8285904c9a60cc91ce21591af17fe.1531332480.git.reinette.chatre@intel.com |
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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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.