• Dan Williams's avatar
    libnvdimm: fix nvdimm_bus_lock() vs device_lock() ordering · 452bae0a
    Dan Williams authored
    A debug patch to turn the standard device_lock() into something that
    lockdep can analyze yielded the following:
    
     ======================================================
     [ INFO: possible circular locking dependency detected ]
     4.11.0-rc4+ #106 Tainted: G           O
     -------------------------------------------------------
     lt-libndctl/1898 is trying to acquire lock:
      (&dev->nvdimm_mutex/3){+.+.+.}, at: [<ffffffffc023c948>] nd_attach_ndns+0x178/0x1b0 [libnvdimm]
    
     but task is already holding lock:
      (&nvdimm_bus->reconfig_mutex){+.+.+.}, at: [<ffffffffc022e0b1>] nvdimm_bus_lock+0x21/0x30 [libnvdimm]
    
     which lock already depends on the new lock.
    
     the existing dependency chain (in reverse order) is:
    
     -> #1 (&nvdimm_bus->reconfig_mutex){+.+.+.}:
            lock_acquire+0xf6/0x1f0
            __mutex_lock+0x88/0x980
            mutex_lock_nested+0x1b/0x20
            nvdimm_bus_lock+0x21/0x30 [libnvdimm]
            nvdimm_namespace_capacity+0x1b/0x40 [libnvdimm]
            nvdimm_namespace_common_probe+0x230/0x510 [libnvdimm]
            nd_pmem_probe+0x14/0x180 [nd_pmem]
            nvdimm_bus_probe+0xa9/0x260 [libnvdimm]
    
     -> #0 (&dev->nvdimm_mutex/3){+.+.+.}:
            __lock_acquire+0x1107/0x1280
            lock_acquire+0xf6/0x1f0
            __mutex_lock+0x88/0x980
            mutex_lock_nested+0x1b/0x20
            nd_attach_ndns+0x178/0x1b0 [libnvdimm]
            nd_namespace_store+0x308/0x3c0 [libnvdimm]
            namespace_store+0x87/0x220 [libnvdimm]
    
    In this case '&dev->nvdimm_mutex/3' mirrors '&dev->mutex'.
    
    Fix this by replacing the use of device_lock() with nvdimm_bus_lock() to protect
    nd_{attach,detach}_ndns() operations.
    
    Cc: <stable@vger.kernel.org>
    Fixes: 8c2f7e86 ("libnvdimm: infrastructure for btt devices")
    Reported-by: default avatarYi Zhang <yizhan@redhat.com>
    Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
    452bae0a
pfn_devs.c 17.5 KB