Messages in this thread | | | Date | Fri, 14 Nov 2003 16:31:31 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: [PATCH] PPC32: cancel syscall restart on signal delivery |
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On Fri, 14 Nov 2003, Linus Torvalds wrote: > > On x86, for the old calling conventions (ie "int 0x80"), that meant that > the interrupt window was literally a single instruction. For the new one > ("sysenter") it was two instructions.
Actually, three instructions for "sysenter": the "movl %esp,%ebp" and the actual "sysenter" instruction itself are the main restart sequence, but to make it look the same as the legacy code from a kernel restart standpoint there is also a short backwards jump there.
Anyway, you can't even trigger it with the single-step flag, since the kernel will disable single-stepping in sysenter (and it only gets re-enabled once the system call is done - including retries).
Since it literally requires an external interrupt to happen, it would be pretty hard to create a test-case for. Maybe a dual-CPU setup with the other CPU sending a signal (and the interrupt is the resultant IPI) at just the right moment..
Linus
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