Hi, I encountered the following issue while booting 5.8-rc1 on Qemu for RV64. I added additional dump_stack and observed that it's happening in bpf free path. It happens always if CONFIG_DEBUG_VM is enabled. VM_BUG_ON_MM is compiled away without that. ------------------------------------------------------------------------ forked to background, child pid 113 [ 10.328850] CPU: 3 PID: 51 Comm: kworker/3:1 Not tainted 5.8.0-rc1-dirty #732 [ 10.331739] Workqueue: events bpf_prog_free_deferred [ 10.334133] Call Trace: [ 10.338039] [<ffffffe000202698>] walk_stackframe+0x0/0xa4 [ 10.339988] [<ffffffe000202880>] show_stack+0x2e/0x3a [ 10.340902] [<ffffffe00047074c>] dump_stack+0x72/0x8c [ 10.341451] [<ffffffe0002db4ce>] mmap_assert_locked.part.13+0x14/0x1c [ 10.342131] [<ffffffe0002db330>] walk_page_range_novma+0x0/0x4e [ 10.342973] [<ffffffe000204f94>] set_direct_map_invalid_noflush+0x66/0x6e [ 10.343917] [<ffffffe0002e0706>] __vunmap+0xe8/0x212 [ 10.344680] [<ffffffe0002e0882>] __vfree+0x22/0x6e [ 10.345270] [<ffffffe0002e0902>] vfree+0x34/0x56 [ 10.345834] [<ffffffe00027d752>] __bpf_prog_free+0x2c/0x36 [ 10.346529] [<ffffffe0002801a2>] bpf_prog_free_deferred+0x74/0x8a [ 10.347394] [<ffffffe000219c70>] process_one_work+0x13a/0x272 [ 10.348239] [<ffffffe00021a4b4>] worker_thread+0x50/0x2e4 [ 10.348900] [<ffffffe00021ed98>] kthread+0xfc/0x10a [ 10.349470] [<ffffffe0002013da>] ret_from_exception+0x0/0xc [ 10.354405] mm ffffffe001018600 mmap 0000000000000000 seqnum 0 task_size 0 [ 10.354405] get_unmapped_area 0000000000000000 [ 10.354405] mmap_base 0 mmap_legacy_base 0 highest_vm_end 0 [ 10.354405] pgd ffffffe001074000 mm_users 2 mm_count 1 pgtables_bytes 8192 map_count 0 [ 10.354405] hiwater_rss 0 hiwater_vm 0 total_vm 0 locked_vm 0 [ 10.354405] pinned_vm 0 data_vm 0 exec_vm 0 stack_vm 0 [ 10.354405] start_code ffffffe000200000 end_code ffffffe00084acc2 start_data 0 end_data ffffffe00106dfe4 [ 10.354405] start_brk 0 brk ffffffe0010bd6d0 start_stack 0 [ 10.354405] arg_start 0 arg_end 0 env_start 0 env_end 0 [ 10.354405] binfmt 0000000000000000 flags 0 core_state 0000000000000000 [ 10.354405] ioctx_table 0000000000000000 [ 10.354405] exe_file 0000000000000000 [ 10.354405] tlb_flush_pending 0 [ 10.354405] def_flags: 0x0() [ 10.369325] ------------[ cut here ]------------ [ 10.370763] kernel BUG at include/linux/mmap_lock.h:81! [ 10.375235] Kernel BUG [#1] [ 10.377198] Modules linked in: [ 10.378931] CPU: 3 PID: 51 Comm: kworker/3:1 Not tainted 5.8.0-rc1-dirty #732 [ 10.380179] Workqueue: events bpf_prog_free_deferred [ 10.381270] epc: ffffffe0002db4d4 ra : ffffffe0002db4d4 sp : ffffffe3eaea7c70 [ 10.382561] gp : ffffffe00106d950 tp : ffffffe3ef752f80 t0 : ffffffe0010836e8 [ 10.383996] t1 : 0000000000000064 t2 : 0000000000000000 s0 : ffffffe3eaea7c90 [ 10.385119] s1 : ffffffe001018600 a0 : 0000000000000289 a1 : 0000000000000020 [ 10.386099] a2 : 0000000000000005 a3 : 0000000000000000 a4 : ffffffe001012758 [ 10.387294] a5 : 0000000000000000 a6 : 0000000000000102 a7 : 0000000000000006 [ 10.388265] s2 : ffffffe3f00674c0 s3 : ffffffe00106e108 s4 : ffffffe00106e100 [ 10.389250] s5 : ffffffe00106e908 s6 : 0000000000000000 s7 : 6db6db6db6db6db7 [ 10.390272] s8 : 0000000000000001 s9 : ffffffe00021a4f8 s10: ffffffffffffffff [ 10.391293] s11: ffffffe3f0066600 t3 : 000000000001a7a8 t4 : 000000000001a7a8 [ 10.392314] t5 : 0000000000000000 t6 : ffffffe00107b76b [ 10.393096] status: 0000000000000120 badaddr: 0000000000000000 cause: 0000000000000003 [ 10.397755] ---[ end trace 861659596ac28841 ]--- ---------------------------------------------------------------------------------------------------
I haven't had the chance to bisect to figure out which commit caused the issue. Just wanted to check if it is a known issue already. Regards, Atish
