On Thu, Nov 19, 2015 at 10:30 PM, Eric Haszlakiewicz <e...@nimenees.com> wrote: > On November 19, 2015 4:28:46 AM EST, Paul Goyette <p...@vps1.whooppee.com> > wrote: >>And if there's anyone who really understands HOW the initial syscall >>gets interrupted when the signal is being delivered (and HOW it gets >>restarted when the handler returns) I would love an explanation! >> > > Regarding restart, I don't think it needs to be explicitly saved anywhere, > because the original call in the userland program has the necessary > information. > > E.g. if you look at the restart path for alpha (just because that's the first > search result I found) you see that it simply moves the userland process' > program counter back a bit, and let's the process trigger the syscall again: > http://nxr.netbsd.org/xref/src/sys/arch/alpha/alpha/syscall.c#203 > > Dunno about how it's actually interrupted though.
My understanding (as of writing this mail) is that, when syscall() receives ERESTART, it updates PC in the trapframe; which will be stored in the signal handler stack by sendsig_siginfo(), and then later be restored by setcontext(2), when signal handler returns from signal trampoline. > > Eric >
