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List:       linux-kernel
Subject:    Re: [PATCH] Remove extra shift in __SI_CODE macro
From:       "Robert H. de Vries" <rhdv () rhdv ! cistron ! nl>
Date:       2000-07-27 22:16:10
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On Sun, 23 Jul 2000, Linus Torvalds wrote:
>On Sun, 23 Jul 2000, Robert H. de Vries wrote:
>> The __SI_CODE macro shifts its argument 16 bits to the left while the only
>> argument used is already shifted 16 bits to the left. In this way no bits
>> are left on a 32 bit architecture.
>> Hence this patch, which removes the superfluous shift.
>
>Sounds like the _users_ of __SI_CODE should be fixed, rather than
>__SI_CODE. The new definition of __SI_CODE doesn't make much sense, in my
>opinion.

If I would change the user, that would trigger an avalanche of changes, while 
my proposition is limited to just one definition.
Let me illustrate:
Suppose I change the user of __SI_CODE: __SI_TIMER. This would imply changing 
it from (1<<16) to 1. 
That would imply changing the entire family for consistency:
#define __SI_KILL       (0 << 16)
#define __SI_TIMER      (1 << 16)
#define __SI_POLL       (2 << 16)
#define __SI_FAULT      (3 << 16)
#define __SI_CHLD       (4 << 16)
#define __SI_RT         (5 << 16)                                             

That would require the change of the following set of definitions:
/*
 * SIGILL si_codes
 */
#define ILL_ILLOPC      (__SI_FAULT|1)  /* illegal opcode */
#define ILL_ILLOPN      (__SI_FAULT|2)  /* illegal operand */
#define ILL_ILLADR      (__SI_FAULT|3)  /* illegal addressing mode */
#define ILL_ILLTRP      (__SI_FAULT|4)  /* illegal trap */
#define ILL_PRVOPC      (__SI_FAULT|5)  /* privileged opcode */
#define ILL_PRVREG      (__SI_FAULT|6)  /* privileged register */
#define ILL_COPROC      (__SI_FAULT|7)  /* coprocessor error */
#define ILL_BADSTK      (__SI_FAULT|8)  /* internal stack error */
#define NSIGILL         8
 
/*
 * SIGFPE si_codes
 */
#define FPE_INTDIV      (__SI_FAULT|1)  /* integer divide by zero */
#define FPE_INTOVF      (__SI_FAULT|2)  /* integer overflow */
#define FPE_FLTDIV      (__SI_FAULT|3)  /* floating point divide by zero */
#define FPE_FLTOVF      (__SI_FAULT|4)  /* floating point overflow */
#define FPE_FLTUND      (__SI_FAULT|5)  /* floating point underflow */
#define FPE_FLTRES      (__SI_FAULT|6)  /* floating point inexact result */
#define FPE_FLTINV      (__SI_FAULT|7)  /* floating point invalid operation */
#define FPE_FLTSUB      (__SI_FAULT|8)  /* subscript out of range */
#define NSIGFPE         8
 
/*
 * SIGSEGV si_codes
 */
#define SEGV_MAPERR     (__SI_FAULT|1)  /* address not mapped to object */
#define SEGV_ACCERR     (__SI_FAULT|2)  /* invalid permissions for mapped 
object */
#define NSIGSEGV        2
 
/*
 * SIGBUS si_codes
 */
#define BUS_ADRALN      (__SI_FAULT|1)  /* invalid address alignment */
#define BUS_ADRERR      (__SI_FAULT|2)  /* non-existant physical address */
#define BUS_OBJERR      (__SI_FAULT|3)  /* object specific hardware error */
#define NSIGBUS         3
 
/*
 * SIGTRAP si_codes
 */
#define TRAP_BRKPT      (__SI_FAULT|1)  /* process breakpoint */
#define TRAP_TRACE      (__SI_FAULT|2)  /* process trace trap */
#define NSIGTRAP        2                                                     
                                  
/*
 * SIGCHLD si_codes
 */
#define CLD_EXITED      (__SI_CHLD|1)   /* child has exited */
#define CLD_KILLED      (__SI_CHLD|2)   /* child was killed */
#define CLD_DUMPED      (__SI_CHLD|3)   /* child terminated abnormally */
#define CLD_TRAPPED     (__SI_CHLD|4)   /* traced child has trapped */
#define CLD_STOPPED     (__SI_CHLD|5)   /* child has stopped */
#define CLD_CONTINUED   (__SI_CHLD|6)   /* stopped child has continued */
#define NSIGCHLD        6
 
/*
 * SIGPOLL si_codes
 */
#define POLL_IN         (__SI_POLL|1)   /* data input available */
#define POLL_OUT        (__SI_POLL|2)   /* output buffers available */
#define POLL_MSG        (__SI_POLL|3)   /* input message available */
#define POLL_ERR        (__SI_POLL|4)   /* i/o error */
#define POLL_PRI        (__SI_POLL|5)   /* high priority input available */
#define POLL_HUP        (__SI_POLL|6)   /* device disconnected */
#define NSIGPOLL        6                                                     
                                  

Plus some 60 changes in various C files (arch/*/kernel/signal*.c).

I thought I was being clever in finding the simplest patch. But then again 
you decide.

	Robert

-- 
Robert de Vries
rhdv@rhdv.cistron.nl

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