In message <200202161628.g1GGSpW10385@mrynet.com>, you write: 

-> I'm now realising that the hangs I'm experiencing on my INDYs are
-> provoked more when building profiled libraries.
[...]
-> Stopped in pid 364 (cc1) at     cpu_Debugger+0x4:       jr      ra
->                 bdslot: nop
-> db> trace

[...this is the call sequence arising from you hitting break...]
-> cpu_Debugger+4 (100,bfbd9830,0,10) ra 88187024 sz 0
-> 88186f54+d0 (100,bfbd9830,0,10) ra 881888b0 sz 48
-> zsc_intr_hard+114 (100,bfbd9830,0,10) ra 88187d14 sz 32
-> 88187cb0+64 (100,bfbd9830,0,10) ra 88189a20 sz 40
-> ip22_mappable_intr+cc (100,bfbd9830,0,10) ra 88189c20 sz 48
-> ip22_local1_intr+b0 (100,bfbd9830,0,10) ra 881898c0 sz 48
-> ip22_intr+d0 (100,bfbd9830,0,10) ra 8818d570 sz 64
-> cpu_intr+48 (100,bfbd9830,0,10) ra 8806a208 sz 32
-> mips3_KernIntr+84 (7fff805e,37d59e,0,37d59e) ra 8817ed1c sz 128

[...and this is actually where it's stuck...]
-> pmap_enter+6ac (7fff805e,37d59e,0,37d59e) ra 88165c3c sz 80
-> uvm_fault+c58 (88cb5d48,7fff8000,0,2) ra 88181360 sz 280
-> trap+4e4 (2000ff13,20c,0,2) ra 88069ec4 sz 72
-> mips3_UserGenException+cc (2000ff13,20c,0,5f7ffc) ra 0 sz 0
-> User-level: pid 364

Are you short of memory or do not have (enough?) swap enabled?  It looks
like UVM is somehow grinding to a halt, and if it is a VM issue, it's
probably not  SGI specific (the pmap code is shared by all mips ports).

This is certainly worth a PR, and it would be interesting to check where
in the code it's stuck (ie, trying to figure out where in uvm_fault()/
pmap_enter() things are when you break in).  I also wonder if the spl
level is somehow out of whack, but then I'd expect more problems; a
register dump would probably prove useful, as might a complete kernel
dump.

--rafal