Messages in this thread | | | Date | Fri, 11 Sep 2015 10:46:36 +0200 | From | Borislav Petkov <> | Subject | Re: [Patch V1] x86, mce: CPU synchronization for broadcast MCE's is surprised by offline CPUs |
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On Thu, Sep 10, 2015 at 08:26:38PM -0400, Ashok Raj wrote: > +#define OFFLINE_CPU_LOG_LEN 16 > + > +struct offline_cpu_mce { > + unsigned short head; > + unsigned short tail; > + struct mce mce_log[OFFLINE_CPU_LOG_LEN]; > +}; > + > +static struct offline_cpu_mce offline_mce; > +static unsigned int offline_mce_overflow = 0; > + > +/* > + * Add mce's discovered in offline cpu which will be logged by the > + * MCE rendezvous master. There is no lock required, since MCE's are > + * processed one cpu at a time, sequenced by the rendezvous master CPU > + * Safe to be called only from MCE handler. > + */ > +static int offline_mce_add(struct mce *m) > +{ > + unsigned next; > + > + next = (offline_mce.tail + 1) % OFFLINE_CPU_LOG_LEN; > + if (next == offline_mce.head) { > + offline_mce_overflow++; > + return -1; > + } > + > + offline_mce.mce_log[offline_mce.tail] = *m; > + offline_mce.tail = next; > + return 0; > +} > + > +static int offline_mce_get(struct mce *m) > +{ > + int ret = 0; > + > + if (offline_mce.head == offline_mce.tail) > + goto out; > + > + *m = offline_mce.mce_log[offline_mce.head]; > + offline_mce.head = (offline_mce.head + 1) % OFFLINE_CPU_LOG_LEN; > + > + ret = 1; > +out: > + return ret; > +}
One more buffer for MCEs? Why?
We did add the mce_gen_pool thing exactly for logging stuff in atomic context. From looking at the code, we probably could get rid of that "struct mce_log mcelog" thing too and use only the gen_pool for logging MCEs.
We can then get rid of that MCE_LOG_LEN arbitrary 32 records and use a nice 2-paged buffer which can be enlarged transparently later, if needed.
Hmmm?
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply.
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