* Rui Nuno Capela <[email protected]> wrote:
> First one is about building for UP (CONFIG_SMP not set) on my old P4
> laptop. As it seems, all my build attempts failed at the final link
> stage, with undefined references to paravirt_enable. After disabling
> CONFIG_PARAVIRT I get a similar failure, but this time for a couple
> kvm* symbols. [...]
ok, i think i have managed to fix both bugs. I have released -rt3,
please re-check whether it works any better. If it still doesnt then
please send me the exact .config that fails.
> [...] I could only get a clean build when CONFIG_SMP is set, which is
> (IMHO) overkill for a machine which is neither HyperThread/SMT enabled
> nor multi-core. Its plain dead UP and it used to run PREEMPT_RT
> kernels for a long time now.
btw., latest SMP kernels (2.6.18 and later) "patch themselves back" to
UP instructions to a high degree if they run on a single CPU - that's
why for example Fedora uses only an SMP kernel these days. Running a
genuine UP kernel is still more efficient - but the difference shouldnt
be /that/ large anymore. (if someone would like to measure it that would
be interesting to see)
> Second one is already about running SMP, on a Dual Core2 T7200, for
> which the build goes fine but run-time is haunted by a crippling BUG:
> Call Trace:
> [<c0102dad>] __switch_to+0xcc/0x176
> [<c01185c8>] wake_up_process+0x19/0x1b
> [<c01fe568>] acpi_ec_gpe_handler+0x1f/0x53
> [<c01ec6c6>] acpi_ev_gpe_dispatch+0x64/0x163
> [<c01eca06>] acpi_ev_gpe_detect+0x94/0xd7
hm, this is a -rt specific thing that i hoped to have worked around but
apparently not. The ACPI code uses a waitqueue in its idle routine
(argh!) which cannot by done sanely on PREEMPT_RT. In -rt3 i've added a
more conservative (but still ugly and incorrect) hack - could you try
it, does -rt3 work any better?
Ingo
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