6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Dave Jiang dave.jiang@intel.com
[ Upstream commit 214291cbaaceeb28debd773336642b1fca393ae0 ]
The following lockdep splat was observed while kernel auto-online a CXL memory region:
====================================================== WARNING: possible circular locking dependency detected 6.17.0djtest+ #53 Tainted: G W ------------------------------------------------------ systemd-udevd/3334 is trying to acquire lock: ffffffff90346188 (hmem_resource_lock){+.+.}-{4:4}, at: hmem_register_resource+0x31/0x50
but task is already holding lock: ffffffff90338890 ((node_chain).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain+0x2e/0x70
which lock already depends on the new lock. [..] Chain exists of: hmem_resource_lock --> mem_hotplug_lock --> (node_chain).rwsem
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- rlock((node_chain).rwsem); lock(mem_hotplug_lock); lock((node_chain).rwsem); lock(hmem_resource_lock);
The lock ordering can cause potential deadlock. There are instances where hmem_resource_lock is taken after (node_chain).rwsem, and vice versa.
Split out the target update section of hmat_register_target() so that hmat_callback() only envokes that section instead of attempt to register hmem devices that it does not need to.
[ dj: Fix up comment to be closer to 80cols. (Jonathan) ]
Fixes: cf8741ac57ed ("ACPI: NUMA: HMAT: Register "soft reserved" memory as an "hmem" device") Reviewed-by: Jonathan Cameron jonathan.cameron@huawei.com Tested-by: Smita Koralahalli Smita.KoralahalliChannabasappa@amd.com Reviewed-by: Smita Koralahalli Smita.KoralahalliChannabasappa@amd.com Reviewed-by: Dan Williams dan.j.williams@intel.com Link: https://patch.msgid.link/20251105235115.85062-3-dave.jiang@intel.com Signed-off-by: Dave Jiang dave.jiang@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/acpi/numa/hmat.c | 46 ++++++++++++++++++++++------------------ 1 file changed, 25 insertions(+), 21 deletions(-)
diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c index 570be52c8d90a..ea620ebd0c7c1 100644 --- a/drivers/acpi/numa/hmat.c +++ b/drivers/acpi/numa/hmat.c @@ -780,10 +780,32 @@ static void hmat_register_target_devices(struct memory_target *target) } }
-static void hmat_register_target(struct memory_target *target) +static void hmat_hotplug_target(struct memory_target *target) { int nid = pxm_to_node(target->memory_pxm);
+ /* + * Skip offline nodes. This can happen when memory marked EFI_MEMORY_SP, + * "specific purpose", is applied to all the memory in a proximity + * domain leading to * the node being marked offline / unplugged, or if + * memory-only "hotplug" node is offline. + */ + if (nid == NUMA_NO_NODE || !node_online(nid)) + return; + + guard(mutex)(&target_lock); + if (target->registered) + return; + + hmat_register_target_initiators(target); + hmat_register_target_cache(target); + hmat_register_target_perf(target, ACCESS_COORDINATE_LOCAL); + hmat_register_target_perf(target, ACCESS_COORDINATE_CPU); + target->registered = true; +} + +static void hmat_register_target(struct memory_target *target) +{ /* * Devices may belong to either an offline or online * node, so unconditionally add them. @@ -801,25 +823,7 @@ static void hmat_register_target(struct memory_target *target) } mutex_unlock(&target_lock);
- /* - * Skip offline nodes. This can happen when memory - * marked EFI_MEMORY_SP, "specific purpose", is applied - * to all the memory in a proximity domain leading to - * the node being marked offline / unplugged, or if - * memory-only "hotplug" node is offline. - */ - if (nid == NUMA_NO_NODE || !node_online(nid)) - return; - - mutex_lock(&target_lock); - if (!target->registered) { - hmat_register_target_initiators(target); - hmat_register_target_cache(target); - hmat_register_target_perf(target, ACCESS_COORDINATE_LOCAL); - hmat_register_target_perf(target, ACCESS_COORDINATE_CPU); - target->registered = true; - } - mutex_unlock(&target_lock); + hmat_hotplug_target(target); }
static void hmat_register_targets(void) @@ -845,7 +849,7 @@ static int hmat_callback(struct notifier_block *self, if (!target) return NOTIFY_OK;
- hmat_register_target(target); + hmat_hotplug_target(target); return NOTIFY_OK; }