From 5a5a48e788e02fd8a8eb7188ce440572d6c12418 Mon Sep 17 00:00:00 2001 From: Vishnu Santhosh Date: Thu, 4 Jun 2026 14:12:53 +0530 Subject: [PATCH] rpmsg: glink: fix deadlock in endpoint destroy during driver detach MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit During driver detach, the device core holds the device mutex throughout the driver's remove callback chain. When the rpmsg endpoint is destroyed as part of that teardown, the GLINK endpoint destroy implementation attempts to unregister the underlying rpmsg device. That unregistration calls device_del(), which tries to re-acquire the same device mutex already held higher up the stack, causing rmmod to hang indefinitely. The deadlock manifests with the following call chain: [<0>] device_del+0x44/0x414  <- tries to acquire same mutex [<0>] device_unregister+0x18/0x34 [<0>] rpmsg_unregister_device+0x28/0x4c [<0>] qcom_glink_remove_rpmsg_device+0x70/0xc0 [<0>] qcom_glink_destroy_ept+0x58/0xbc [<0>] rpmsg_dev_remove+0x50/0x60 [<0>] device_remove+0x4c/0x80 [<0>] device_release_driver_internal+0x1cc/0x228 <- acquires device mutex [<0>] driver_detach+0x4c/0x98 [<0>] bus_remove_driver+0x6c/0xbc [<0>] driver_unregister+0x30/0x60 [<0>] unregister_rpmsg_driver+0x10/0x1c [<0>] fastrpc_exit+0x28/0x38 [fastrpc] [<0>] __arm64_sys_delete_module+0x1b8/0x294 [<0>] invoke_syscall+0x48/0x10c [<0>] el0_svc_common.constprop.0+0xc0/0xe0 [<0>] do_el0_svc+0x1c/0x28 [<0>] el0_svc+0x34/0x108 [<0>] el0t_64_sync_handler+0xa0/0xe4 [<0>] el0t_64_sync+0x198/0x19c The rpmsg device unregistration inside endpoint destroy is redundant. In both contexts where endpoint destruction is triggered: - Driver detach path: the driver core already tears down the rpmsg device. - Channel close path: the rpmsg device is already unregistered before endpoint destruction is reached. Remove the redundant unregistration to fix the deadlock. Co-developed-by: Deepak Kumar Singh Signed-off-by: Deepak Kumar Singh Signed-off-by: Vishnu Santhosh Tested-by: Bjorn Andersson Fixes: a53e356df548 ("rpmsg: glink: fix rpmsg device leak") Reviewed-by: Dmitry Baryshkov Link: https://lore.kernel.org/r/20260604-rpmsg-glink-fix-deadlock-destroy-ept-v1-1-b8a54ad1e4fd@oss.qualcomm.com Signed-off-by: Bjorn Andersson --- drivers/rpmsg/qcom_glink_native.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c index 022b4bcb40d6..55793fc18293 100644 --- a/drivers/rpmsg/qcom_glink_native.c +++ b/drivers/rpmsg/qcom_glink_native.c @@ -1418,9 +1418,6 @@ static void qcom_glink_destroy_ept(struct rpmsg_endpoint *ept) channel->ept.cb = NULL; spin_unlock_irqrestore(&channel->recv_lock, flags); - /* Decouple the potential rpdev from the channel */ - qcom_glink_remove_rpmsg_device(glink, channel); - qcom_glink_send_close_req(glink, channel); }