Messages in this thread | | | Subject | Re: [PATCH -v4] x86: MCE: Re-implement MCE log ring buffer as per-CPU ring buffer | From | Huang Ying <> | Date | Mon, 08 Jun 2009 10:05:21 +0800 |
| |
On Mon, 2009-06-08 at 09:17 +0800, Hidetoshi Seto wrote: > Huang Ying wrote: > > On Fri, 2009-06-05 at 16:28 +0800, Hidetoshi Seto wrote: > >> Huang Ying wrote: > >>> On Fri, 2009-06-05 at 15:01 +0800, Hidetoshi Seto wrote: > >>>> Huang Ying wrote: > >>>>> struct mce_log { > >>>>> - char signature[12]; /* "MACHINECHECK" */ > >>>>> + char signature[12]; /* "MACHINECHEC2" */ > >>>>> unsigned len; /* = MCE_LOG_LEN */ > >>>>> - unsigned next; > >>>>> unsigned flags; > >>>>> unsigned pad0; > >>>>> - struct mce entry[MCE_LOG_LEN]; > >>>>> + struct mce_log_cpu *mcelog_cpus; > >>>>> }; > >>>> What is this *mcelog_cpus to be used for? > >>>> It seems it will point one of per-CPU buffers (maybe cpu#0's buffer) > >>>> if I have read the following mce_log_init() correctly. > >>> It is mainly used by something like kdump, which can search > >>> "MACHINECHEC2", and analyze mce_log. mcelog_cpus can help kdump find the > >>> real mcelog storage. > >> Hum, but it help tools only to find one of buffers, not to find all. > >> > >> I think it would be better help for tools if we have another signature > >> on struct mce_log_cpu, e.g.: > >> > >> +struct mce_log_cpu { > >> + char signature[**]; /* "MCE_LOG_CPU_VER_1" or so */ > >> + __u32 cpuid; /* cpuid or extcpu, same as struct mce */ > >> + int head; > >> + int tail; > >> + unsigned long flags; > >> + struct mce entry[MCE_LOG_LEN]; > >> +}; > >> > >> How about this? > > > > + mcelog.mcelog_cpus = &per_cpu_var(mce_log_cpus); > > > > So mcelog.mcelog_cpus are pointed to the buffers of all CPUs, not just > > that of one CPU. You can find them by analyzing PER cpu data structure. > > I thought that the signature is used to find the structure without such > analyzing. If a tool can analyze PER cpu data, then it likely know > where the mce_log_cpu is, so mcelog.mcelog_cpus will not be required. > > #define per_cpu_var(var) per_cpu__##var > > #define per_cpu(var, cpu) \ > (*SHIFT_PERCPU_PTR(&per_cpu_var(var), per_cpu_offset(cpu))) > > OK, I have mistook per_cpu_var() for per_cpu(). > Then mcelog.mcelog_cpus does not point any of the buffers, but tells where > the buffer is locating in each of PER cpu data. > Tools have to get per_cpu_offset(cpu) to know where the PER cpu data > allocated. According to pcpu_alloc_bootmem(), it might consider NUMA. > Anyway It will take a bit more effort. > > So still I think the mcelog.mcelog_cpus is mostly pointless.
Emm, it seem hard to analyze mce_log_cpu from per_cpu_var(mce_log_cpus), how about following method:
struct mce_log { char signature[12]; ... struct mce_log_cpu *mcelog_cpus[]; };
void mcelog_init(void) { int cpu; mcelog.mcelog_cpus = kmalloc(sizeof(void *) * num_possible_cpus(); for_each_possible_cpu(cpu) mcelog.mcelog_cpus[cpu] = &per_cpu(mce_log_cpus, cpu); }
Best Regards, Huang Ying
| |