Subject: Re: [PATCH] [POWERPC] Rework EXC_LEVEL_EXCEPTION_PROLOG code

From: Scott Wood <[email-masked]>
Date: Thu, 01 May 2008 14:02:55 -0500

Kumar Gala wrote:
> copying the flags isn't the issue.  Its acting on the flags thats the 
> problem.  I'm not 100% sure the C code that might clear the flags is 
> consistent on how it access them.  

Actually *delivering* the signal should never be done except when 
returning to user.  That's different from sending the signal, though.

BTW, it doesn't seem all that unreasonable for a kernel 
profiling/tracing exception to signal a process that, for example, an 
event buffer is over a certain threshold.

 > So if one bit of code clears
 > task_struct->stack->thread_info->flags and other clears
 > thread_info(STACK)->flags we get into an issue on how to merge after
 > that.

It appears that TIF_SIGPENDING is always accessed through the task 
struct, though not so for TIF_NEED_RESCHED.

-Scott