> UML seems to be badly broken 2.6.34 onwards - leading to random segfaults.
>
> Reading symbols from /home/parag/devel/kernel/linux-2.6-um/linux...done.
> (gdb) r
> Starting program: /home/parag/devel/kernel/linux-2.6-um/linux
> Checking that ptrace can change system call numbers...OK
> Checking syscall emulation patch for ptrace...OK
> Checking advanced syscall emulation patch for ptrace...OK
> Checking for tmpfs mount on /dev/shm...OK
> Checking PROT_EXEC mmap in /dev/shm/...OK
> Checking for the skas3 patch in the host:
> - /proc/mm...not found: No such file or directory
> - PTRACE_FAULTINFO...not found
> - PTRACE_LDT...not found
> UML running in SKAS0 mode
> Core dump limits :
> soft - 0
> hard - NONE
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x000000006007823f in alloc_kmemlist (cachep=0x61c00f40, limit=<value
> optimized out>, batchcount=<value optimized out>, shared=<value optimized
> out>, gfp=208) at mm/slab.c:3861
> 3861 l3->free_limit = (1 + nr_cpus_node(node)) *
> (gdb)
>
> (gdb) bt
> #0 0x000000006007823f in alloc_kmemlist (cachep=0x61c00f40, limit=<value
> optimized out>, batchcount=<value optimized out>, shared=<value optimized
> out>, gfp=208) at mm/slab.c:3861
> #1 do_tune_cpucache (cachep=0x61c00f40, limit=<value optimized out>,
> batchcount=<value optimized out>, shared=<value optimized out>, gfp=208)
> at mm/slab.c:3943
> #2 0x00000000600783be in enable_cpucache (cachep=0x61c00f40,
> gfp=1639983680) at mm/slab.c:3993
> #3 0x000000006016e43d in setup_cpu_cache (cachep=0x61c00f40, gfp=208) at
> mm/slab.c:2017
> #4 0x0000000060078797 in kmem_cache_create (name=0x601c80b6
> "idr_layer_cache", size=<value optimized out>, align=<value optimized
> out>, flags=262144, ctor=<value optimized out>)
> at mm/slab.c:2351
> #5 0x000000006000982c in idr_init_cache () at lib/idr.c:676
> #6 0x00000000600015df in start_kernel () at init/main.c:658
>
> This one I tried to debug and something weird seems to be going on -
>
> mm/slab.c:3849 does a l3 = kmalloc_node(...), which *seems* to be
> returning NULL but the check on next line - if (!l3) doesn't seem to be
> succeeding.
>
> Finally it seems to happily dereference l3 (0x40 offsets etc.) up until
> dereferencing free_limit at which point it explodes.
>
> A very few times it goes a little further and explodes at
>
> fsck from util-linux-ng 2.16
> ROOT: clean, 18550/65536 files, 106443/262144 blocks
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x00000000600effb7 in cfq_close_cooperator (cfqd=0x7fcbe000,
> cur_cfqq=0x7ff81bb0) at block/cfq-iosched.c:1801
> 1801 if (cfq_class_rt(cfqq) != cfq_class_rt(cur_cfqq))
> (gdb) p cfqq
> = (struct cfq_queue *) 0x0
> (gdb) p cur_cfqq
> = (struct cfq_queue *) 0x7ff81bb0
> (gdb)
>
> This is with CONFIG_SLAB=y.
>
> Parag
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to
majordomo@vger.kernel.org
> More majordomo info at
http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at
http://www.tux.org/lkml/
>
