On 8/16/25 7:35 PM, Sudarsan Mahendran wrote: > > > On Sat, Aug 16, 2025 at 1:06 AM Harry Yoo <[email protected] > <mailto:[email protected]>> wrote: >> >> On Fri, Aug 15, 2025 at 03:53:00PM -0700, Sudarsan Mahendran wrote: >> > Hi Vlastimil, >> > >> > I ported this patch series on top of v6.17. >> > I had to resolve some merge conflicts because of >> > fba46a5d83ca8decb338722fb4899026d8d9ead2 >> > >> > The conflict resolution looks like: >> > >> > @@ -5524,20 +5335,19 @@ EXPORT_SYMBOL_GPL(mas_store_prealloc); >> > int mas_preallocate(struct ma_state *mas, void *entry, gfp_t gfp) >> > { >> > MA_WR_STATE(wr_mas, mas, entry); >> > - int ret = 0; >> > - int request; >> > >> > mas_wr_prealloc_setup(&wr_mas); >> > mas->store_type = mas_wr_store_type(&wr_mas); >> > - request = mas_prealloc_calc(&wr_mas, entry); >> > - if (!request) >> > + mas_prealloc_calc(&wr_mas, entry); >> > + if (!mas->node_request) >> > goto set_flag; >> > >> > mas->mas_flags &= ~MA_STATE_PREALLOC; >> > - mas_node_count_gfp(mas, request, gfp); >> > + mas_alloc_nodes(mas, gfp); >> > if (mas_is_err(mas)) { >> > - mas_set_alloc_req(mas, 0); >> > - ret = xa_err(mas->node); >> > + int ret = xa_err(mas->node); >> > + >> > + mas->node_request = 0; >> > mas_destroy(mas); >> > mas_reset(mas); >> > return ret; >> > @@ -5545,7 +5355,7 @@ int mas_preallocate(struct ma_state *mas, void > *entry, gfp_t gfp) >> > >> > set_flag: >> > mas->mas_flags |= MA_STATE_PREALLOC; >> > - return ret; >> > + return 0; >> > } >> > EXPORT_SYMBOL_GPL(mas_preallocate); >> > >> > >> > >> > When I try to boot this kernel, I see kernel panic >> > with rcu_free_sheaf() doing recursion into __kmem_cache_free_bulk() >> > >> > Stack trace: >> > >> > [ 1.583673] Oops: stack guard page: 0000 [#1] SMP NOPTI >> > [ 1.583676] CPU: 103 UID: 0 PID: 0 Comm: swapper/103 Not tainted > 6.17.0-smp-sheaves2 #1 NONE >> > [ 1.583679] RIP: 0010:__kmem_cache_free_bulk+0x57/0x540 >> > [ 1.583684] Code: 48 85 f6 0f 84 b8 04 00 00 49 89 d6 49 89 ff 48 > 85 ff 0f 84 fe 03 00 00 49 83 7f 08 00 0f 84 f3 03 00 00 0f 1f 44 00 00 > 31 c0 <48> 89 44 24 18 65 8b 05 6d 26 dc 02 89 44 24 2c 31 ff 89 f8 c7 44 >> > [ 1.583685] RSP: 0018:ff40dbc49b048fc0 EFLAGS: 00010246 >> > [ 1.583687] RAX: 0000000000000000 RBX: 0000000000000012 RCX: > ffffffff939e8640 >> > [ 1.583687] RDX: ff2afe75213e6c90 RSI: 0000000000000012 RDI: > ff2afe750004ad00 >> > [ 1.583688] RBP: ff40dbc49b049130 R08: ff2afe75368c2500 R09: > ff2afe75368c3b00 >> > [ 1.583689] R10: ff2afe75368c2500 R11: ff2afe75368c3b00 R12: > ff2aff31ba00b000 >> > [ 1.583690] R13: ffffffff939e8640 R14: ff2afe75213e6c90 R15: > ff2afe750004ad00 >> > [ 1.583690] FS: 0000000000000000(0000) GS:ff2aff31ba00b000(0000) > knlGS:0000000000000000 >> > [ 1.583691] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> > [ 1.583692] CR2: ff40dbc49b048fb8 CR3: 0000000017c3e001 CR4: > 0000000000771ef0 >> > [ 1.583692] PKRU: 55555554 >> > [ 1.583693] Call Trace: >> > [ 1.583694] <IRQ> >> > [ 1.583696] __kmem_cache_free_bulk+0x2c7/0x540 >> >> [..] >> >> > [ 1.583759] __kmem_cache_free_bulk+0x2c7/0x540 >> >> Hi Sudarsan, thanks for the report. >> >> I'm not really sure how __kmem_cache_free_bulk() can call itself. >> There's no recursion of __kmem_cache_free_bulk() in the code. > Hi Harry, > > I assume somehow the free_to_pcs_bulk() fallback case is taken, thus > calling __kmem_cache_free_bulk(), which calls free_to_pcs_bulk() ad nauseam.
Could it be a rebase gone wrong? Mine to 6.17-rc1 is here (but untested) https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/ > free_to_pcs_bulk() > { > ... > fallback: > __kmem_cache_free_bulk(s, size, p); > ... > } > > static void __kmem_cache_free_bulk(struct kmem_cache *s, size_t size, > void **p) I don't have this, this codes seems to correspond to my kmem_cache_free_bulk(), while __kmem_cache_free_bulk() is just build_detached_freelist() and do_slab_free() with no sheaves involved. > { > if (!size) > return; > > /* > * freeing to sheaves is so incompatible with the detached > freelist so > * once we go that way, we have to do everything differently > */ > if (s && s->cpu_sheaves) { > free_to_pcs_bulk(s, size, p); > return; > } > ... > > Thanks Greg for pointing this out. > > >> As v6.17-rc1 is known to cause a few surprising bugs, could you please >> rebase onto of mm-hotfixes-unstable and check if it still reproduces? >> >> > [ 1.583761] ? update_group_capacity+0xad/0x1f0 >> > [ 1.583763] ? sched_balance_rq+0x4f6/0x1e80 >> > [ 1.583765] __kmem_cache_free_bulk+0x2c7/0x540 >> > [ 1.583767] ? update_irq_load_avg+0x35/0x480 >> > [ 1.583768] ? __pfx_rcu_free_sheaf+0x10/0x10 >> > [ 1.583769] rcu_free_sheaf+0x86/0x110 >> > [ 1.583771] rcu_do_batch+0x245/0x750 >> > [ 1.583772] rcu_core+0x13a/0x260 >> > [ 1.583773] handle_softirqs+0xcb/0x270 >> > [ 1.583775] __irq_exit_rcu+0x48/0xf0 >> > [ 1.583776] sysvec_apic_timer_interrupt+0x74/0x80 >> > [ 1.583778] </IRQ> >> > [ 1.583778] <TASK> >> > [ 1.583779] asm_sysvec_apic_timer_interrupt+0x1a/0x20 >> > [ 1.583780] RIP: 0010:cpuidle_enter_state+0x101/0x290 >> > [ 1.583781] Code: 85 f4 ff ff 49 89 c4 8b 73 04 bf ff ff ff ff e8 > d5 44 d4 ff 31 ff e8 9e c7 37 ff 80 7c 24 04 00 74 05 e8 12 45 d4 ff fb > 85 ed <0f> 88 ba 00 00 00 89 e9 48 6b f9 68 4c 8b 44 24 08 49 8b 54 38 30 >> > [ 1.583782] RSP: 0018:ff40dbc4809afe80 EFLAGS: 00000202 >> > [ 1.583782] RAX: ff2aff31ba00b000 RBX: ff2afe75614b0800 RCX: > 000000005e64b52b >> > [ 1.583783] RDX: 000000005e73f761 RSI: 0000000000000067 RDI: > 0000000000000000 >> > [ 1.583783] RBP: 0000000000000002 R08: fffffffffffffff6 R09: > 0000000000000000 >> > [ 1.583784] R10: 0000000000000380 R11: ffffffff908c38d0 R12: > 000000005e64b535 >> > [ 1.583784] R13: 000000005e5580da R14: ffffffff92890b10 R15: > 0000000000000002 >> > [ 1.583784] ? __pfx_read_tsc+0x10/0x10 >> > [ 1.583787] cpuidle_enter+0x2c/0x40 >> > [ 1.583788] do_idle+0x1a7/0x240 >> > [ 1.583790] cpu_startup_entry+0x2a/0x30 >> > [ 1.583791] start_secondary+0x95/0xa0 >> > [ 1.583794] common_startup_64+0x13e/0x140 >> > [ 1.583796] </TASK> >> > [ 1.583796] Modules linked in: >> > [ 1.583798] ---[ end trace 0000000000000000 ]--- >> > [ 1.583798] RIP: 0010:__kmem_cache_free_bulk+0x57/0x540 >> > [ 1.583800] Code: 48 85 f6 0f 84 b8 04 00 00 49 89 d6 49 89 ff 48 > 85 ff 0f 84 fe 03 00 00 49 83 7f 08 00 0f 84 f3 03 00 00 0f 1f 44 00 00 > 31 c0 <48> 89 44 24 18 65 8b 05 6d 26 dc 02 89 44 24 2c 31 ff 89 f8 c7 44 >> > [ 1.583800] RSP: 0018:ff40dbc49b048fc0 EFLAGS: 00010246 >> > [ 1.583801] RAX: 0000000000000000 RBX: 0000000000000012 RCX: > ffffffff939e8640 >> > [ 1.583801] RDX: ff2afe75213e6c90 RSI: 0000000000000012 RDI: > ff2afe750004ad00 >> > [ 1.583801] RBP: ff40dbc49b049130 R08: ff2afe75368c2500 R09: > ff2afe75368c3b00 >> > [ 1.583802] R10: ff2afe75368c2500 R11: ff2afe75368c3b00 R12: > ff2aff31ba00b000 >> > [ 1.583802] R13: ffffffff939e8640 R14: ff2afe75213e6c90 R15: > ff2afe750004ad00 >> > [ 1.583802] FS: 0000000000000000(0000) GS:ff2aff31ba00b000(0000) > knlGS:0000000000000000 >> > [ 1.583803] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> > [ 1.583803] CR2: ff40dbc49b048fb8 CR3: 0000000017c3e001 CR4: > 0000000000771ef0 >> > [ 1.583803] PKRU: 55555554 >> > [ 1.583804] Kernel panic - not syncing: Fatal exception in interrupt >> > [ 1.584659] Kernel Offset: 0xf600000 from 0xffffffff81000000 > (relocation range: 0xffffffff80000000-0xffffffffbfffffff) >> > >> >
