Need help in figuring out why gdb gives different value of a variable in callee vs caller context

[Richi Dubey]

Thanks a lot! This is why get_highest_ready was causing problems. I
couldn't have figured it out by myself.

On Mon, Aug 17, 2020 at 4:14 AM Gedare Bloom <gedare at rtems.org> wrote:

> This is wrong:
> https://github.com/richidubey/rtems/blob/c3162134d3fd7d4d46ec01609d81bdb62bc818af/cpukit/score/src/schedulerstrongapa.c#L182
>
> It assumes the Chain_Node is at the start of the struct
> Scheduler_strong_APA_Node.
>
> On Sun, Aug 16, 2020 at 11:34 AM Richi Dubey <richidubey at gmail.com> wrote:
> >
> > Hi,
> >
> > The gdb trace above refers to this code where the items in all_Nodes
> chain are checked. The items in the chain are getting inserted here, before
> which on line 763, the Affinity of the items is set to all the online
> processors. Why does the gdb show the Affinity of the node as 0 then? How
> is this possible? Please advise.
> >
> > On Sun, Aug 16, 2020 at 5:48 PM Richi Dubey <richidubey at gmail.com>
> wrote:
> >>
> >> Oh, I printed the variable value too early. Thanks for your help.
> >>
> >> On Sat, Aug 15, 2020 at 7:24 PM Gedare Bloom <gedare at rtems.org> wrote:
> >>>
> >>> On Sat, Aug 15, 2020 at 3:15 AM Richi Dubey <richidubey at gmail.com>
> wrote:
> >>> >
> >>> > Hi,
> >>> >
> >>> > With reference to the code (github link), it aims to check if the
> Affinty of a node is set to 0 by calling the function
> _Processor_mask_Is_zero.
> >>> >
> >>> > While debugging with gdb, I can see using 'p' command that the
> variable is indeed 0 but after the variable gets passed to the function,
> the value of the variable isn't 0 anymore. Why is this happening?
> >>> >
> >>> > Gdb trace:
> >>> >
> ----------------------------------------------------------------------
> >>> > (gdb)
> >>> > 0x00118af4 187         _Processor_mask_Is_set(&node->Affinity,
> _Per_CPU_Get_index(curr_CPU) ||
> >>> > (gdb)
> >>> > 0x00118af6 187         _Processor_mask_Is_set(&node->Affinity,
> _Per_CPU_Get_index(curr_CPU) ||
> >>> > (gdb) p &node->Affinity
> >>> > $8 = (Processor_mask *) 0x200efc <_Thread_Objects+2172>
> >>> address 0x200efc
> >>>
> >>> > (gdb) p node->Affinity
> >>> > $9 = {
> >>> >   __bits = {0}
> >>> > }
> >>> > (gdb) si
> >>> > 0x00118af8 187         _Processor_mask_Is_set(&node->Affinity,
> _Per_CPU_Get_index(curr_CPU) ||
> >>> > (gdb)
> >>> > 190         _Processor_mask_Is_zero( &node->Affinity ) )
> >>> > (gdb)
> >>> > 0x00118afc 190         _Processor_mask_Is_zero( &node->Affinity ) )
> >>> > (gdb)
> >>> > 0x00118afe 190         _Processor_mask_Is_zero( &node->Affinity ) )
> >>> > (gdb)
> >>> > 0x00118b00 190         _Processor_mask_Is_zero( &node->Affinity ) )
> >>> > (gdb)
> >>> > _Processor_mask_Is_zero (mask=0x203580 <_Per_CPU_Information>) at
> /home/richi/quick-start/src/rtems/cpukit/include/rtems/score/processormask.h:75
> >>> > 75 {
> >>> > (gdb)
> >>> > 0x0011726a 75 {
> >>> > (gdb)
> >>> > 0x0011726c 75 {
> >>> > (gdb) p mask
> >>> > $10 = (const Processor_mask *) 0x203580 <_Per_CPU_Information>
> >>> address 0x203580
> >>>
> >>> You're not looking at the same memory location
> >>>
> >>> > (gdb) p *mask
> >>> > $11 = {
> >>> >   __bits = {2126656}
> >>> > }
> >>> > ------------------------------------------------------------
> >>> >
> >>> > Please provide your views on this.
> >>> > Thanks,
> >>> > Richi,
> >>> > _______________________________________________
> >>> > devel mailing list
> >>> > devel at rtems.org
> >>> > http://lists.rtems.org/mailman/listinfo/devel
>
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