Stefan, Am Montag, 21. Mai 2018, 04:29:24 CEST schrieb Stefan Schaeckeler: > Hello Richard and others, > > > I get the use-case, but why is this only for mtdoops? > > Powerpc's nvram module also stores oops messages and does so by adding an > additional timestamp, as well (search for kmsg_dump_get_buffer() in > arch/powerpc/kernel/nvram_64.c).
Just one more reason to make it generic. > This timestamp is the number of seconds since 1970 and stored as a 64 bit > integer in the nvram header. Basically, the last kmesg timestamp is a few ms > less than this additionally stored timestamp. Recording boottime would be more > elegant, I guess. > > > > IMHO this needs to go into generic code such that all kmsg dumpers can > > benefit from it. > > This would be not that easy: > > #1 kmsg_dump_get_buffer(...size...) returns the most recent <size> bytes. > Consecutive calls return older chunks. It would be natural to return the > boottime as the first line, e.g. in the last call, but some clients such as > mtdoops call kmsg_dump_get_buffer() only once. The returned buffer may be > complete including boottime, or not. > > #2 consistency with other clients: nvram_64.c has the same requirement of > storing a kind of wall-time but does it in a completely different way: no > readable ascii text timestamp preprended to the kmsg buffer but a 64 bit > timestamp in its header. Note, I don't think we should make mtdoops behave > like > nvram_64.c by storing the timestamp as a 64 bit integer (in its header) b/c > most people do a cat or string of the mtd device /dev/mtdX and a 64 bit > integer > would just read as garbage. I think this is the perfect opportunity to talk with other kmesg dump users on how to add a timestamp. As last resort we can always do it in our own way but I think making it generic is at lest worth a try... > I hope we can have separate implementations for recording additional > timestamps. Later, I'll send a patch with stylistic changes unless we > completely disagree on how to move forward. Both #1 and #2 aren't show-stoppers. Thanks, //richard
