Question on SI_ASYNCIO

From: Sukadev Bhattiprolu
Date: Tue Dec 02 2008 - 23:03:43 EST


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

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