[patch] only update dcache after write succeeds
Marc Khouzam
marc.khouzam@ericsson.com
Mon Sep 14 19:29:00 GMT 2009
> -----Original Message-----
> From: Michael Snyder [mailto:msnyder@vmware.com]
> Sent: Monday, September 14, 2009 3:27 PM
> To: Doug Evans
> Cc: gdb-patches@sourceware.org; Marc Khouzam; Greg Law; Pedro
> Alves; Hui Zhu
> Subject: Re: [patch] only update dcache after write succeeds
>
> Doug Evans wrote:
> > Hi.
> >
> > Marc, Greg: Can you see if this patch fixes things for you?
>
> Hey Doug,
>
> I tested this change, and it does indeed seem to fix the problem
> with target record -- but. ;-)
>
> Part of the reason that it works is that record_xfer_partial
> calls error() instead of returning -1. If I change it so that
> it returns -1, things get more complicated.
Just a note that PRecord used to return -1 which caused memory
to be changed even when the query was answered with 'n'.
That is why Hui changed it to error()
>
> The do-while loop that used to follow and now preceeds this code
> calls target-beneath, which in our case results in several different
> target methods being called, one of which eventually returns > 0.
>
> That just means that in the present case, calling error is correct.
> But I worry about some of the other cases where the target method
> returns -1, and whether badness might occur in some other cases.
>
> Michael
>
>
> > 2009-09-14 Doug Evans <dje@google.com>
> >
> > * target.c (memory_xfer_partial): Only update dcache
> after we know
> > the write succeeded.
> >
> > Index: target.c
> > ===================================================================
> > RCS file: /cvs/src/src/gdb/target.c,v
> > retrieving revision 1.223
> > diff -u -p -r1.223 target.c
> > --- target.c 8 Sep 2009 23:52:45 -0000 1.223
> > +++ target.c 14 Sep 2009 19:11:38 -0000
> > @@ -1289,19 +1289,6 @@ memory_xfer_partial (struct target_ops *
> > }
> > }
> >
> > - /* Make sure the cache gets updated no matter what - if
> we are writing
> > - to the stack, even if this write is not tagged as
> such, we still need
> > - to update the cache. */
> > -
> > - if (inf != NULL
> > - && readbuf == NULL
> > - && !region->attrib.cache
> > - && stack_cache_enabled_p
> > - && object != TARGET_OBJECT_STACK_MEMORY)
> > - {
> > - dcache_update (target_dcache, memaddr, (void *)
> writebuf, reg_len);
> > - }
> > -
> > /* If none of those methods found the memory we wanted, fall back
> > to a target partial transfer. Normally a single call to
> > to_xfer_partial is enough; if it doesn't recognize an object
> > @@ -1331,6 +1318,20 @@ memory_xfer_partial (struct target_ops *
> > if (readbuf && !show_memory_breakpoints)
> > breakpoint_restore_shadows (readbuf, memaddr, reg_len);
> >
> > + /* Make sure the cache gets updated no matter what - if
> we are writing
> > + to the stack. Even if this write is not tagged as
> such, we still need
> > + to update the cache. */
> > +
> > + if (res > 0
> > + && inf != NULL
> > + && writebuf != NULL
> > + && !region->attrib.cache
> > + && stack_cache_enabled_p
> > + && object != TARGET_OBJECT_STACK_MEMORY)
> > + {
> > + dcache_update (target_dcache, memaddr, (void *)
> writebuf, reg_len);
> > + }
> > +
> > /* If we still haven't got anything, return the last error. We
> > give up. */
> > return res;
>
>
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