Commits
Reinette Chatre committed 2989360d9c6
x86/intel_rdt: Fix possible circular lock dependency
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