From 53989fad1286e652ea3655ae3367ba698da8d2ff Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Thu, 11 Nov 2021 10:19:05 -0800 Subject: cxl/pmem: Fix module reload vs workqueue state A test of the form: while true; do modprobe -r cxl_pmem; modprobe cxl_pmem; done May lead to a crash signature of the form: BUG: unable to handle page fault for address: ffffffffc0660030 #PF: supervisor instruction fetch in kernel mode #PF: error_code(0x0010) - not-present page [..] Workqueue: cxl_pmem 0xffffffffc0660030 RIP: 0010:0xffffffffc0660030 Code: Unable to access opcode bytes at RIP 0xffffffffc0660006. [..] Call Trace: ? process_one_work+0x4ec/0x9c0 ? pwq_dec_nr_in_flight+0x100/0x100 ? rwlock_bug.part.0+0x60/0x60 ? worker_thread+0x2eb/0x700 In that report the 0xffffffffc0660030 address corresponds to the former function address of cxl_nvb_update_state() from a previous load of the module, not the current address. Fix that by arranging for ->state_work in the 'struct cxl_nvdimm_bridge' object to be reinitialized on cxl_pmem module reload. Details: Recall that CXL subsystem wants to link a CXL memory expander device to an NVDIMM sub-hierarchy when both a persistent memory range has been registered by the CXL platform driver (cxl_acpi) *and* when that CXL memory expander has published persistent memory capacity (Get Partition Info). To this end the cxl_nvdimm_bridge driver arranges to rescan the CXL bus when either of those conditions change. The helper bus_rescan_devices() can not be called underneath the device_lock() for any device on that bus, so the cxl_nvdimm_bridge driver uses a workqueue for the rescan. Typically a driver allocates driver data to hold a 'struct work_struct' for a driven device, but for a workqueue that may run after ->remove() returns, driver data will have been freed. The 'struct cxl_nvdimm_bridge' object holds the state and work_struct directly. Unfortunately it was only arranging for that infrastructure to be initialized once per device creation rather than the necessary once per workqueue (cxl_pmem_wq) creation. Introduce is_cxl_nvdimm_bridge() and cxl_nvdimm_bridge_reset() in support of invalidating stale references to a recently destroyed cxl_pmem_wq. Cc: Fixes: 8fdcb1704f61 ("cxl/pmem: Add initial infrastructure for pmem support") Reported-by: Vishal Verma Tested-by: Vishal Verma Link: https://lore.kernel.org/r/163665474585.3505991.8397182770066720755.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Dan Williams --- drivers/cxl/pmem.c | 29 +++++++++++++++++++++++++++-- 1 file changed, 27 insertions(+), 2 deletions(-) (limited to 'drivers/cxl/pmem.c') diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c index 17e82ae90456..b65a272a2d6d 100644 --- a/drivers/cxl/pmem.c +++ b/drivers/cxl/pmem.c @@ -315,6 +315,31 @@ static struct cxl_driver cxl_nvdimm_bridge_driver = { .id = CXL_DEVICE_NVDIMM_BRIDGE, }; +/* + * Return all bridges to the CXL_NVB_NEW state to invalidate any + * ->state_work referring to the now destroyed cxl_pmem_wq. + */ +static int cxl_nvdimm_bridge_reset(struct device *dev, void *data) +{ + struct cxl_nvdimm_bridge *cxl_nvb; + + if (!is_cxl_nvdimm_bridge(dev)) + return 0; + + cxl_nvb = to_cxl_nvdimm_bridge(dev); + device_lock(dev); + cxl_nvb->state = CXL_NVB_NEW; + device_unlock(dev); + + return 0; +} + +static void destroy_cxl_pmem_wq(void) +{ + destroy_workqueue(cxl_pmem_wq); + bus_for_each_dev(&cxl_bus_type, NULL, NULL, cxl_nvdimm_bridge_reset); +} + static __init int cxl_pmem_init(void) { int rc; @@ -340,7 +365,7 @@ static __init int cxl_pmem_init(void) err_nvdimm: cxl_driver_unregister(&cxl_nvdimm_bridge_driver); err_bridge: - destroy_workqueue(cxl_pmem_wq); + destroy_cxl_pmem_wq(); return rc; } @@ -348,7 +373,7 @@ static __exit void cxl_pmem_exit(void) { cxl_driver_unregister(&cxl_nvdimm_driver); cxl_driver_unregister(&cxl_nvdimm_bridge_driver); - destroy_workqueue(cxl_pmem_wq); + destroy_cxl_pmem_wq(); } MODULE_LICENSE("GPL v2"); -- cgit v1.2.3