Linux 3.0 x86_64: When is SIGSTKFLT raised?

Question

Under what circumstances (if any) would the signal SIGSTKFLT be synchronously raised by the kernel under Linux 3.0 on x86_64 ?

Answer 1

According to man 7 signal:

 Signal       Value     Action   Comment

SIGSTKFLT    -,16,-     Term    Stack fault on coprocessor (unused)

Since the x86 coprocessor stack cannot fault (I'm pretty sure), I don't think it can be signaled implicitly. Only explicit generation (by kill() or raise()) could cause it.

I grep'd the kernel source. It does not use it, but there are about 50 instances (per CPU architecture) of

#define SIGSTKFLT   16