On Fri, Feb 04, 2005 at 02:00:15PM +1100, Keith Owens wrote: > On Thu, 3 Feb 2005 20:09:57 -0600, > Jack Steiner <[EMAIL PROTECTED]> wrote: > >On Thu, Feb 03, 2005 at 05:48:26PM -0600, Russ Anderson wrote: > >> According to the SAL Spec, MCAs are supposed to be handled > >> one at a time. > > > >It has been a long time since I looked, but I thought the > >spec allowed either implemention, ie. serialize OR all-at-once. > > > >Maybe I'm remembering the error handling guide but I know > >I have seen this somewhere..... > > It is ambiguous. Extracts from SAL spec. > > 4.1.1 says only one processor gets OS_MCA. > > When multiple processors experience machine checks simultaneously, > SAL selects a "monarch" machine check processor to accumulate all the > error records at the platform level and continue with the machine > check processing. "Monarch" status is relevant only for the current > MCA error event. > > 4.7.2 (5) also says only one processor. > > 5. SAL selects a monarch for handling the error. All slaves > processors in SAL_MC_RENDEZ check in their status with the SAL on > the monarch. > > But the last sentence of 4.7.2 (8) refers to multiple processors in OS > MCA. > > 8. SAL finishes the MCA handling on all the processors that are in > MCA and waits for all the processors in MCA to synchronize before > branching to OS MCA for further processing. Note that the > hand-off to OS MCA from SAL MCA occurs simultaneously on all > processors executing in SAL MCA handler. > > 4.7.2 (9) lets the OS choose the monarch, which implies that more than > one cpu can be in OS MCA handler. > > 9. OS_MCA may choose a monarch processor to continue with error > handling. After OS_MCA completes the error handling, the monarch > processor wakes up all the slaves through a wake-up message as > shown by (9) in Figure 4-4 > > The end of 4.7.3 also implies that OS MCA handler can be running on > multiple cpus. Note 'on all the processors'. > > When multiple processors experience machine checks simultaneously, > SAL selects a monarch machine check processor to accumulate all the > error records at the platform level. Once this is done, the OS_MCA > procedure will take control of further error handling on all the > processors that experienced the machine checks. The OS_MCA layer may > need to implement a similar monarch processor selection for the error > recovery phase. The operating system will be aware of which > processors invoked the SAL_MC_RENDEZ procedure in response to the > MC_rendezvous interrupt or the INIT signal and shall wake up those > processors.
To further muddy the waters, it looks like the latest Error Handling Guide has addressed the issue: >> Intel® Itanium® Processor Family Error Handling Guide April 2004 >> >> Document Number: 249278-003 >> >> 2.7.1 >> >> ... >> The MCA error information is provided to the OS_MCA layer. The MCA >> error record is logged to the NVM. To simplify SAL implementation, it >> is strongly recommended that SAL process all MCAs by handing off to the >> OS as soon as possible to prevent some OSes from experiencing time-outs >> and potentially crashing the system. >>>> The SAL may maintain a variable in >> the SAL data area that indicates whether SAL, on one of the processors, >> is already handling an MCA. If so, MCA processing on other processors will >> wait within the SAL MCA handler until the current MCA is processed. This >> situation may arise when local MCAs are experienced on multiple >> processors. <<<<<<< However, it says "may maintain a variable...". Should I interpret this as allowing but not requiring serialization? -- Thanks Jack Steiner ([EMAIL PROTECTED]) 651-683-5302 Principal Engineer SGI - Silicon Graphics, Inc. - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
