Question on SI_ASYNCIO

[Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>]

Hi,

SI_ASYNCIO is defined in include/asm-generic/siginfo.h as:

	#define SI_ASYNCIO      -4              /* sent by AIO completion */

The negative value makes it a 'user-space' signal according to 

	#define SI_FROMUSER(siptr)      ((siptr)->si_code <= 0)
	#define SI_FROMKERNEL(siptr)    ((siptr)->si_code > 0)

But this signal is generated in the kernel async_completed() -
drivers/usb/core/devio.c

Am trying to understand why this is considered as a user-space signal ?

Isn't SI_ASYNCIO similar to SI_POLL or SI_MESGQ - both of which are
'kernel-signals' ?

POSIX.1 explicitly ignores async io. 

Thanks,

Sukadev