On Tue, Nov 01, 2022 at 09:20:21AM +0000, John Thomson wrote: > On Tue, 1 Nov 2022, at 07:57, Feng Tang wrote: > > Hi Thomson, > > > > Thanks for testing! > > > > + mips maintainer and mail list. The original report is here > > > > https://lore.kernel.org/lkml/becf2ac3-2a90-4f3a-96d9-a70f67c66e4a@xxxxxxxxxxxxxxxx/ > > I am guessing my issue comes from __kmem_cache_alloc_lru accessing s->object_size when (kmem_cache) s is NULL? > If that is the case, this change is not to blame, it only exposes the issue? > > I get the following dmesg (note very early NULL kmem_cache) with the below change atop v6.1-rc3: > > transfer started ......................................... transfer ok, time=2.02s > setting up elf image... OK > jumping to kernel code > zimage at: 80B842A0 810B4EFC > > Uncompressing Linux at load address 80001000 > > Copy device tree to address 80B80EE0 > > Now, booting the kernel... > > [ 0.000000] Linux version 6.1.0-rc3+ (john@john) (mipsel-buildroot-linux-gnu-gcc.br_real (Buildroot 2021.11-4428-g6b6741b) 12.2.0, GNU ld (GNU Binutils) 2.39) #61 SMP Tue Nov 1 18:04:13 AEST 2022 > [ 0.000000] slub: kmem_cache_alloc called with kmem_cache: 0x0 > [ 0.000000] slub: __kmem_cache_alloc_lru called with kmem_cache: 0x0 > [ 0.000000] SoC Type: MediaTek MT7621 ver:1 eco:3 > [ 0.000000] printk: bootconsole [early0] enabled > [ 0.000000] CPU0 revision is: 0001992f (MIPS 1004Kc) > [ 0.000000] MIPS: machine is MikroTik RouterBOARD 760iGS > > normal boot > > > diff --git a/mm/slub.c b/mm/slub.c > index 157527d7101b..10fcdf2520d2 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -3410,7 +3410,13 @@ static __always_inline > void *__kmem_cache_alloc_lru(struct kmem_cache *s, struct list_lru *lru, > gfp_t gfpflags) > { > - void *ret = slab_alloc(s, lru, gfpflags, _RET_IP_, s->object_size); > + void *ret; > + if (IS_ERR_OR_NULL(s)) { > + pr_warn("slub: __kmem_cache_alloc_lru called with kmem_cache: %pSR\n", s); > + ret = slab_alloc(s, lru, gfpflags, _RET_IP_, 0); > + } else { > + ret = slab_alloc(s, lru, gfpflags, _RET_IP_, s->object_size); > + } > > trace_kmem_cache_alloc(_RET_IP_, ret, s, gfpflags, NUMA_NO_NODE); > > @@ -3419,6 +3425,8 @@ void *__kmem_cache_alloc_lru(struct kmem_cache *s, struct list_lru *lru, > > void *kmem_cache_alloc(struct kmem_cache *s, gfp_t gfpflags) > { > + if (IS_ERR_OR_NULL(s)) > + pr_warn("slub: kmem_cache_alloc called with kmem_cache: %pSR\n", s); > return __kmem_cache_alloc_lru(s, NULL, gfpflags); > } > EXPORT_SYMBOL(kmem_cache_alloc); > @@ -3426,6 +3434,8 @@ EXPORT_SYMBOL(kmem_cache_alloc); > void *kmem_cache_alloc_lru(struct kmem_cache *s, struct list_lru *lru, > gfp_t gfpflags) > { > + if (IS_ERR_OR_NULL(s)) > + pr_warn("slub: __kmem_cache_alloc_lru called with kmem_cache: %pSR\n", s); > return __kmem_cache_alloc_lru(s, lru, gfpflags); > } > EXPORT_SYMBOL(kmem_cache_alloc_lru); > > > Any hints on where kmem_cache_alloc would be being called from this early? > I will start looking from /init/main.c around pr_notice("%s", linux_banner); Great. Would you try calling dump_stack(); when we observed s == NULL? That would give more information about who passed s == NULL to these functions. -- Thanks, Hyeonggon
