6.12-stable review patch. If anyone has any objections, please let me know.
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From: Sudeep Holla sudeep.holla@arm.com
[ Upstream commit 9ca7a421229bbdfbe2e1e628cff5cfa782720a10 ]
The current use of a mutex to protect the notifier hashtable accesses can lead to issues in the atomic context. It results in the below kernel warnings:
| BUG: sleeping function called from invalid context at kernel/locking/mutex.c:258 | in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 9, name: kworker/0:0 | preempt_count: 1, expected: 0 | RCU nest depth: 0, expected: 0 | CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0 Not tainted 6.14.0 #4 | Workqueue: ffa_pcpu_irq_notification notif_pcpu_irq_work_fn | Call trace: | show_stack+0x18/0x24 (C) | dump_stack_lvl+0x78/0x90 | dump_stack+0x18/0x24 | __might_resched+0x114/0x170 | __might_sleep+0x48/0x98 | mutex_lock+0x24/0x80 | handle_notif_callbacks+0x54/0xe0 | notif_get_and_handle+0x40/0x88 | generic_exec_single+0x80/0xc0 | smp_call_function_single+0xfc/0x1a0 | notif_pcpu_irq_work_fn+0x2c/0x38 | process_one_work+0x14c/0x2b4 | worker_thread+0x2e4/0x3e0 | kthread+0x13c/0x210 | ret_from_fork+0x10/0x20
To address this, replace the mutex with an rwlock to protect the notifier hashtable accesses. This ensures that read-side locking does not sleep and multiple readers can acquire the lock concurrently, avoiding unnecessary contention and potential deadlocks. Writer access remains exclusive, preserving correctness.
This change resolves warnings from lockdep about potential sleep in atomic context.
Cc: Jens Wiklander jens.wiklander@linaro.org Reported-by: Jérôme Forissier jerome.forissier@linaro.org Closes: https://github.com/OP-TEE/optee_os/issues/7394 Fixes: e0573444edbf ("firmware: arm_ffa: Add interfaces to request notification callbacks") Message-Id: 20250528-ffa_notif_fix-v1-3-5ed7bc7f8437@arm.com Reviewed-by: Jens Wiklander jens.wiklander@linaro.org Tested-by: Jens Wiklander jens.wiklander@linaro.org Signed-off-by: Sudeep Holla sudeep.holla@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/firmware/arm_ffa/driver.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c index 33f7bdb5c86dd..134e77a646cc1 100644 --- a/drivers/firmware/arm_ffa/driver.c +++ b/drivers/firmware/arm_ffa/driver.c @@ -110,7 +110,7 @@ struct ffa_drv_info { struct work_struct sched_recv_irq_work; struct xarray partition_info; DECLARE_HASHTABLE(notifier_hash, ilog2(FFA_MAX_NOTIFICATIONS)); - struct mutex notify_lock; /* lock to protect notifier hashtable */ + rwlock_t notify_lock; /* lock to protect notifier hashtable */ };
static struct ffa_drv_info *drv_info; @@ -1223,19 +1223,19 @@ static int __ffa_notify_relinquish(struct ffa_device *dev, int notify_id, if (notify_id >= FFA_MAX_NOTIFICATIONS) return -EINVAL;
- mutex_lock(&drv_info->notify_lock); + write_lock(&drv_info->notify_lock);
rc = update_notifier_cb(dev, notify_id, NULL, is_framework); if (rc) { pr_err("Could not unregister notification callback\n"); - mutex_unlock(&drv_info->notify_lock); + write_unlock(&drv_info->notify_lock); return rc; }
if (!is_framework) rc = ffa_notification_unbind(dev->vm_id, BIT(notify_id));
- mutex_unlock(&drv_info->notify_lock); + write_unlock(&drv_info->notify_lock);
return rc; } @@ -1275,7 +1275,7 @@ static int __ffa_notify_request(struct ffa_device *dev, bool is_per_vcpu, else cb_info->cb = cb;
- mutex_lock(&drv_info->notify_lock); + write_lock(&drv_info->notify_lock);
if (!is_framework) { if (is_per_vcpu) @@ -1295,7 +1295,7 @@ static int __ffa_notify_request(struct ffa_device *dev, bool is_per_vcpu, }
out_unlock_free: - mutex_unlock(&drv_info->notify_lock); + write_unlock(&drv_info->notify_lock); if (rc) kfree(cb_info);
@@ -1344,16 +1344,16 @@ static void handle_notif_callbacks(u64 bitmap, enum notify_type type) if (!(bitmap & 1)) continue;
- mutex_lock(&drv_info->notify_lock); + read_lock(&drv_info->notify_lock); cb_info = notifier_hnode_get_by_type(notify_id, type); - mutex_unlock(&drv_info->notify_lock); + read_unlock(&drv_info->notify_lock);
if (cb_info && cb_info->cb) cb_info->cb(notify_id, cb_info->cb_data); } }
-static void notif_get_and_handle(void *unused) +static void notif_get_and_handle(void *cb_data) { int rc; struct ffa_notify_bitmaps bitmaps; @@ -1800,7 +1800,7 @@ static void ffa_notifications_setup(void) goto cleanup;
hash_init(drv_info->notifier_hash); - mutex_init(&drv_info->notify_lock); + rwlock_init(&drv_info->notify_lock);
drv_info->notif_enabled = true; return;