Willy Tarreau <[EMAIL PROTECTED]> writes: > On Sat, Apr 14, 2007 at 07:54:33PM +0200, Ingo Molnar wrote: >> >> * Eric W. Biederman <[EMAIL PROTECTED]> wrote: >> >> > > Thinking about it, I don't know if there are calls to schedule() >> > > while switching from tty1 to tty2. Alt-F2 had no effect anymore, and >> > > "chvt 2" simply blocked. It would have been possible that a >> > > schedule() call somewhere got starved due to the load, I don't know. >> > >> > It looks like there is a call to schedule_work. >> >> so this goes over keventd, right? >> >> > There are two pieces of the path. If you are switching in and out of a >> > tty controlled by something like X. User space has to grant >> > permission before the operation happens. Where there isn't a gate >> > keeper I know it is cheaper but I don't know by how much, I suspect >> > there is still a schedule happening in there. >> >> Could keventd perhaps be starved? Willy, to exclude this possibility, >> could you perhaps chrt keventd to RT priority? If events/0 is PID 5 then >> the command to set it to SCHED_FIFO:50 would be: >> >> chrt -f -p 50 5 >> >> but ... events/0 is reniced to -5 by default, so it should definitely >> not be starved. > > Well, since I merged the fair-fork patch, I cannot reproduce (in fact, > bash forks 1000 processes, then progressively execs scheddos, but it > takes some time). So I'm rebuilding right now. But I think that Linus > has an interesting clue about GPM and notification before switching > the terminal. I think it was enabled in console mode. I don't know > how that translates to frozen xterms, but let's attack the problems > one at a time.
I think it is a good clue. However the intention of the mechanism is that only processes that change the video mode on a VT are supposed to use it. So I really don't think gpm is the culprit. However it easily could be something else that has similar characteristics. I just realized we do have proof that schedule_work is actually working because SAK works, and we can't sanely do SAK from interrupt context so we call schedule work. Eric - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
