we used to only test the checksum of the PCMP structure referenced by
the _MP_ without checking _MP_ itself. now fixed.
geoff added some coherence() calls and comments in the mpstartup and
apic code which seems to be a good idea.
replace the various functions that searched for bios data structures by
a single sigsearch() one in pc/memory.c that will probe the various bios
data areas.
also, a new checksum() function was added that is to be used to validate
the structures found.
always make sure that there are child processes we can wait for
before sleeping.
put pwait() sleep into a loop and recheck. this is not strictly
neccesary but prevents accidents if there are spurious wakeups
or a bug.
once we set q->done = 1 in mountmux, the sleeper might return freeing q
so the wakeup might access invalid memory. we change the embedded Rendez
structure in the Mntrpc into a pointer to the sleeping procs up->sleep
rendez so the rendez is always going to be valid even if the rpc has been
freed.
the call to mntstats was moved before we set q->done also to prevent
accessing invalid memory.
wakeup cannot access r->sleep once we set r->done because the
sleeper might just return at this point making r invalid. make
a copy of the sleep rendez pointer before setting r->done.
allow the shadow framebuffer (softscreen) to be used with any
vga driver, not just vesa. this removes the ugly scr->paddr = 0
hack employed by vesa driver to force softscreen and adds a
softscreen vgactl message that can switch the feature on and off
at runtime.
softscreen can greatly improve graphics performance when bus
reads are slow even tho it disables hardware acceleration.
the limit for overqueueing was too small for stuff like fcp
on a fileserver connected with a standard 32K limit pipe like
ramfs.
fcp usesd 8K*16procs > 32K*2
the biggest queue limit used in the kernel is 256K making
the maximum queue bloat 2.5MB or 320K for standard pipes.
that should be big enougth to never happen in practice
unless there is a bug which we like to catch before we
exhaust all kernel memory.
