On Wed, 2005-10-26 at 16:27 -0400, Dave Anderson wrote: > Badari Pulavarty wrote: > > > On Wed, 2005-10-26 at 14:41 -0400, Dave Anderson wrote: > > > Sorry I've generated some unnecesary confusion re: my comments > > > about the use of DEFINE_PER_CPU and DECLARE_PER_CPU. > > > That's what I get for trying to multi-task... > > > > > > Stepping back, the init_tss array is defined in "arch/x86_64/kernel/init_task.c". > > > > > > In 2.6.9, it's declared like so: > > > > > > /* > > > * per-CPU TSS segments. Threads are completely 'soft' on Linux, > > > * no more per-task TSS's. The TSS size is kept cacheline-aligned > > > * so they are allowed to end up in the .data.cacheline_aligned > > > * section. Since TSS's are completely CPU-local, we want them > > > * on exact cacheline boundaries, to eliminate cacheline ping-pong. > > > */ > > > DEFINE_PER_CPU(struct tss_struct, init_tss) ____cacheline_maxaligned_in_smp; > > > > > > In 2.6.13, it's slightly different in that it is initialized to INIT_TSS: > > > > > > /* > > > * per-CPU TSS segments. Threads are completely 'soft' on Linux, > > > * no more per-task TSS's. The TSS size is kept cacheline-aligned > > > * so they are allowed to end up in the .data.cacheline_aligned > > > * section. Since TSS's are completely CPU-local, we want them > > > * on exact cacheline boundaries, to eliminate cacheline ping-pong. > > > */ > > > DEFINE_PER_CPU(struct tss_struct, init_tss) ____cacheline_maxaligned_in_smp = INIT_TSS; > > > > > > Both kernels have the same DECLARE_PER_CPU in the > > > "x86_64/processor.h" header file: > > > > > > DECLARE_PER_CPU(struct tss_struct,init_tss); > > > > > > That being the case, and not seeing why the INIT_TSS initialization should > > > have anything to do with the problem at hand, I am officially stumped at > > > why the 2.6.14 kernel shows the problem with your patch. > > > > Okay, I thought so too. I will take a closer look at it and let you > > know what I find. I am tempted to go back to 2.6.10 and see if > > crash works. Do you know the last known good kernel release for crash > > to work ? > > > > Sorry -- for x86_64, I can't say that I do know the last version > that worked. Maybe somebody else on the list that uses other > than Red Hat RHEL4 kernels does? > > Dave > Dave, I tried 2.6.10 and crash worked fine there. Here is the what I found interesting. On 2.6.10 the values seem reasonable, but on 2.6.14 they have huge values. 2.6.10: cpunum: 0 data_offset 10084b80f60 cpunum: 1 data_offset 10084b88f60 2.6.14-rc5: cpunum: 0 data_offset ffff810084af5f60 cpunum: 1 data_offset ffff810084afdf60 I got curious on the top "0xffff8" part an trimmed them. (basically I did data_offset & 0x00000fffffffffff). Now I run into next problem :( I am missing something basic. crash: read error: kernel virtual address: ffff81000000fa90 type: "pglist_data node_next" Thanks, Badari
