RE: [RFC PATCH v7 2/8] dpll: Add DPLL framework base functions
flat view
From: "Kubalewski, Arkadiusz" <arkadiusz.kubalewski@intel.com>
Date: 2023-06-09 12:55:52
Also in:
linux-arm-kernel, linux-clk
From: Jiri Pirko <jiri@resnulli.us> Sent: Tuesday, May 9, 2023 3:40 PM Fri, Apr 28, 2023 at 02:20:03AM CEST, vadfed@meta.com wrote:quoted
From: Vadim Fedorenko <vadim.fedorenko@linux.dev>[...]quoted
+int dpll_pre_dumpit(struct netlink_callback *cb) +{ + mutex_lock(&dpll_xa_lock);Did you test this? I'm gettting following deadlock warning: [ 280.899789] ====================================================== [ 280.900458] WARNING: possible circular locking dependency detected [ 280.901126] 6.3.0jiri+ #4 Tainted: G L [ 280.901702] ------------------------------------------------------ [ 280.902378] python3/1058 is trying to acquire lock: [ 280.902934] ffff88811571ae88 (nlk_cb_mutex-GENERIC){+.+.}-{3:3}, at: netlink_dump+0x4a/0x400 [ 280.903869] but task is already holding lock: [ 280.904559] ffffffff827d1c68 (dpll_xa_lock){+.+.}-{3:3}, at: dpll_pin_pre_dumpit+0x13/0x20 [ 280.905464] which lock already depends on the new lock. [ 280.906414] the existing dependency chain (in reverse order) is: [ 280.907141] -> #1 (dpll_xa_lock){+.+.}-{3:3}: [ 280.907711] __mutex_lock+0x91/0xbb0 [ 280.908116] dpll_pin_pre_dumpit+0x13/0x20 [ 280.908553] genl_start+0xc6/0x150 [ 280.908940] __netlink_dump_start+0x158/0x230 [ 280.909399] genl_family_rcv_msg_dumpit+0xf9/0x110 [ 280.909894] genl_rcv_msg+0x115/0x290 [ 280.910302] netlink_rcv_skb+0x54/0x100 [ 280.910726] genl_rcv+0x24/0x40 [ 280.911106] netlink_unicast+0x182/0x260 [ 280.911547] netlink_sendmsg+0x242/0x4b0 [ 280.911984] sock_sendmsg+0x38/0x60 [ 280.912384] __sys_sendto+0xeb/0x130 [ 280.912797] __x64_sys_sendto+0x20/0x30 [ 280.913227] do_syscall_64+0x3c/0x80 [ 280.913639] entry_SYSCALL_64_after_hwframe+0x46/0xb0 [ 280.914156] -> #0 (nlk_cb_mutex-GENERIC){+.+.}-{3:3}: [ 280.914809] __lock_acquire+0x1165/0x26b0 [ 280.915254] lock_acquire+0xce/0x2b0 [ 280.915665] __mutex_lock+0x91/0xbb0 [ 280.916080] netlink_dump+0x4a/0x400 [ 280.916488] __netlink_dump_start+0x188/0x230 [ 280.916953] genl_family_rcv_msg_dumpit+0xf9/0x110 [ 280.917448] genl_rcv_msg+0x115/0x290 [ 280.917863] netlink_rcv_skb+0x54/0x100 [ 280.918301] genl_rcv+0x24/0x40 [ 280.918686] netlink_unicast+0x182/0x260 [ 280.919129] netlink_sendmsg+0x242/0x4b0 [ 280.919569] sock_sendmsg+0x38/0x60 [ 280.919969] __sys_sendto+0xeb/0x130 [ 280.920377] __x64_sys_sendto+0x20/0x30 [ 280.920808] do_syscall_64+0x3c/0x80 [ 280.921220] entry_SYSCALL_64_after_hwframe+0x46/0xb0 [ 280.921730] other info that might help us debug this: [ 280.922513] Possible unsafe locking scenario: [ 280.923095] CPU0 CPU1 [ 280.923541] ---- ---- [ 280.923976] lock(dpll_xa_lock); [ 280.924329] lock(nlk_cb_mutex-GENERIC); [ 280.924916] lock(dpll_xa_lock); [ 280.925454] lock(nlk_cb_mutex-GENERIC); [ 280.925858] *** DEADLOCK *** [ 280.926488] 2 locks held by python3/1058: [ 280.926891] #0: ffffffff827e2430 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 [ 280.927585] #1: ffffffff827d1c68 (dpll_xa_lock){+.+.}-{3:3}, at: dpll_pin_pre_dumpit+0x13/0x20 [ 280.928385] stack backtrace: [ 280.928853] CPU: 8 PID: 1058 Comm: python3 Tainted: G L 6.3.0jiri+ #4 [ 280.929586] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 [ 280.930558] Call Trace: [ 280.930849] <TASK> [ 280.931117] dump_stack_lvl+0x58/0xb0 [ 280.931500] check_noncircular+0x11b/0x130 [ 280.931916] ? kernel_text_address+0x109/0x110 [ 280.932353] __lock_acquire+0x1165/0x26b0 [ 280.932759] lock_acquire+0xce/0x2b0 [ 280.933130] ? netlink_dump+0x4a/0x400 [ 280.933517] __mutex_lock+0x91/0xbb0 [ 280.933885] ? netlink_dump+0x4a/0x400 [ 280.934269] ? netlink_dump+0x4a/0x400 [ 280.934662] ? netlink_dump+0x4a/0x400 [ 280.935054] netlink_dump+0x4a/0x400 [ 280.935426] __netlink_dump_start+0x188/0x230 [ 280.935857] genl_family_rcv_msg_dumpit+0xf9/0x110 [ 280.936321] ? genl_family_rcv_msg_attrs_parse.constprop.0+0xe0/0xe0 [ 280.936887] ? dpll_nl_pin_get_doit+0x100/0x100 [ 280.937324] ? genl_lock_dumpit+0x50/0x50 [ 280.937729] genl_rcv_msg+0x115/0x290 [ 280.938109] ? dpll_pin_post_doit+0x20/0x20 [ 280.938526] ? dpll_nl_pin_get_doit+0x100/0x100 [ 280.938966] ? dpll_pin_pre_dumpit+0x20/0x20 [ 280.939390] ? genl_family_rcv_msg_doit.isra.0+0x110/0x110 [ 280.939904] netlink_rcv_skb+0x54/0x100 [ 280.940296] genl_rcv+0x24/0x40 [ 280.940636] netlink_unicast+0x182/0x260 [ 280.941034] netlink_sendmsg+0x242/0x4b0 [ 280.941439] sock_sendmsg+0x38/0x60 [ 280.941804] ? sockfd_lookup_light+0x12/0x70 [ 280.942230] __sys_sendto+0xeb/0x130 [ 280.942616] ? mntput_no_expire+0x7e/0x490 [ 280.943038] ? proc_nr_files+0x30/0x30 [ 280.943425] __x64_sys_sendto+0x20/0x30 [ 280.943817] do_syscall_64+0x3c/0x80 [ 280.944194] entry_SYSCALL_64_after_hwframe+0x46/0xb0 [ 280.944674] RIP: 0033:0x7f252fd132b0 [ 280.945042] Code: c0 ff ff ff ff eb b8 0f 1f 00 f3 0f 1e fa 41 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 1d 45 31 c9 45 31 c0 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 68 c3 0f 1f 80 00 00 00 00 41 54 48 83 ec 20 [ 280.946622] RSP: 002b:00007ffdbd9335d8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c [ 280.947328] RAX: ffffffffffffffda RBX: 00007ffdbd933688 RCX: 00007f252fd132b0 [ 280.947962] RDX: 0000000000000014 RSI: 00007f252ede65d0 RDI: 0000000000000003 [ 280.948594] RBP: 00007f252f806da0 R08: 0000000000000000 R09: 0000000000000000 [ 280.949229] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 [ 280.949858] R13: ffffffffc4653600 R14: 0000000000000001 R15: 00007f252f74d147 [ 280.950494] </TASK> Problem is that in __netlink_dump_start() you take dpll_xa_lock (in control->start(cb)) while holding nlk->cb_mutex, then you unlock the nlk->cb_mutex and take it again in netlink_dump(). I hear "Chiquitita" from the distance :) [...]
Well I tested it, but haven't seen such outcome, do you have any script for reproducing this behavior? Thank you, Arkadiusz