Note that single-stepping of smp code at instruction-level might affect the timing of the execution. During single-stepping, only one core is advanced while the others stay halted. If you are trying to catch a race condition then the timing impact might change the program behavior. Shorter bursts of single-stepping will usually not have any side-effect as the default execution slot for each cpu is 50 clocks, but it might be good be aware of this behavior ...
Jiri. On 7/2/20 10:32 AM, Richi Dubey wrote: > Yeah, this makes a lot of sense. > Mr. Huber also told me a similar story about qemu using -O0 optimizations > which are easier to debug. > > Thank you. > > On Wed, Jul 1, 2020 at 8:03 PM Gedare Bloom <ged...@rtems.org > <mailto:ged...@rtems.org>> wrote: > > On Wed, Jul 1, 2020 at 5:32 AM Richi Dubey <richidu...@gmail.com > <mailto:richidu...@gmail.com>> wrote: > > > > Dear Dr. Gaisler, > > > > There's something that I am getting stuck at while trying to debug an > smp03 (https://git.rtems.org/rtems/tree/testsuites/smptests/smp03/init.c) > test suite with gdb running on sis. > > > > I started sis with the command: > > > ------------------------------------------------------------------------------------------------------------------- > > > > $ ./sparc-rtems5-sis -leon3 -m 4 -gdb > > > > SIS - SPARC/RISCV instruction simulator 2.21, copyright Jiri Gaisler > 2019 > > Bug-reports to j...@gaisler.se <mailto:j...@gaisler.se> > > > > LEON3 emulation enabled, 4 cpus online, delta 50 clocks > > > > gdb: listening on port 1234 > > > ------------------------------------------------------------------------------------------------------------------- > > and gdb with the command: > > > > > ------------------------------------------------------------------------------------------------------------------- > > $ ./sparc-rtems5-gdb > ~/quick-start/build/b-smp-leon3/sparc-rtems5/c/leon3/testsuites/smptests/smp03.exe > > . > > . > > . > > Reading symbols from > /home/richi/quick-start/build/b-smp-leon3/sparc-rtems5/c/leon3/testsuites/smptests/smp03.exe... > > (gdb) target extended-remote localhost:1234 > > Remote debugging using localhost:1234 > > 0x00000000 in ?? () > > (gdb) load > > Loading section .text, size 0x20440 lma 0x40000000 > > Loading section .rtemsroset, size 0x90 lma 0x40020440 > > Loading section .data, size 0x690 lma 0x40028500 > > Start address 0x40000000, load size 133984 > > Transfer rate: 1063 KB/sec, 271 bytes/write. > > (gdb) b _Scheduler_EDF_SMP_Get_highest_ready > > Breakpoint 1 at 0x4000e620: _Scheduler_EDF_SMP_Get_highest_ready. (4 > locations) > > (gdb) continue > > Continuing. > > > > Breakpoint 1, _Scheduler_EDF_SMP_Get_highest_ready (filter=0x40029000 > <_RTEMS_tasks_Objects+576>, > > context=0x4002bc28 <_Configuration_Scheduler_EDF_SMP_dflt>) > > at > /home/richi/quick-start/src/rtems/c/src/../../cpukit/score/src/scheduleredfsmp.c:151 > > 151 self = _Scheduler_EDF_SMP_Get_self( context ); > > (gdb) stepi > > 0x4000e624 151 self = _Scheduler_EDF_SMP_Get_self( context ); > > (gdb) stepi > > RBTree_Control_RB_MINMAX (val=-1, head=head@entry=0x4002bc74 > <_Configuration_Scheduler_EDF_SMP_dflt+76>) > > at > /home/richi/quick-start/src/rtems/c/src/../../cpukit/score/src/rbtreenext.c:37 > > 37 { > > (gdb) stepi > > 0x4001787c 37 { > > (gdb) stepi > > 0x40017880 37 { > > (gdb) stepi > > 0x40017884 37 { > > (gdb) stepi > > 0x40017890 37 { > > (gdb) stepi > > 0x40017894 37 { > > (gdb) stepi > > _RBTree_Minimum (tree=tree@entry=0x4002bc74 > <_Configuration_Scheduler_EDF_SMP_dflt+76>) > > at > /home/richi/quick-start/src/rtems/c/src/../../cpukit/score/src/rbtreenext.c:39 > > 39 } > > (gdb) stepi > > 0x400178a0 39 } > > (gdb) stepi > > 0x400178a4 39 } > > (gdb) stepi > > 0x400178a8 39 } > > (gdb) stepi > > 0x4000e628 in _Scheduler_EDF_SMP_Get_highest_ready (filter=0x40029000 > <_RTEMS_tasks_Objects+576>, > > context=0x4002bc28 <_Configuration_Scheduler_EDF_SMP_dflt>) > > at > /home/richi/quick-start/src/rtems/c/src/../../cpukit/score/src/scheduleredfsmp.c:151 > > 151 self = _Scheduler_EDF_SMP_Get_self( context ); > > (gdb) stepi > > 164 > > (gdb) stepi > > 0x4000e630 164 > > (gdb) stepi > > 0x4000e634 164 > > (gdb) stepi > > 0x4000e638 164 > > (gdb) stepi > > 175 > > (gdb) stepi > > 0x4000e694 175 > > (gdb) > > > ------------------------------------------------------------------------------------------------------------------- > > Now I can't figure out why gdb won't show me the next instruction after > 151 self = _Scheduler_EDF_SMP_Get_self( context );? Why is it jumping to > instruction 164 and later to 175? What might be going wrong? Please let me > know. > > > > This can happen because of compiler optimizations. The order of the > assembly instructions in the program does not need to match exactly > the order in the source code, and some source lines might not have any > assembly associated with them. You can turn off optimization, or you > can compare the debug execution with the assembly program, to try to > get some more insight. > > > Thanks, > > Richi. > > > > On Fri, May 29, 2020 at 12:55 PM Richi Dubey <richidu...@gmail.com > <mailto:richidu...@gmail.com>> wrote: > >> > >> Thanks a lot! It is working now after I set appropriate breakpoints. > >> > >> On Tue, May 26, 2020 at 11:58 PM Jiri Gaisler <j...@gaisler.se > <mailto:j...@gaisler.se>> wrote: > >> > > >> > > >> > On 5/26/20 2:55 PM, Richi Dubey wrote: > >> > > Hii, > >> > > > >> > > Thank you for your replies. I did not load the program before > >> > > executing run on gdb. Now it works fine. > >> > > > >> > > However, I need your help with one more thing. When I run gdb with > >> > > stepi or nexti to see how the code runs from the beginning to the > end, > >> > > gdb always ends up going in an infinite loop in hard_reset () at > >> > > > /home/richi/quick-start/src/rtems/c/src/lib/libbsp/sparc/leon3/../../../../../../bsps/sparc/shared/start/start.S:274 > >> > > while only executing the following commands: > >> > > > >> > > 371 std %g0,[%g2] > >> > > (gdb) > >> > > 372 add %g2,8,%g2 > >> > > (gdb) > >> > > 373 cmp %g2,%g3 > >> > > (gdb) > >> > > 374 bleu,a zerobss > >> > > (gdb) > >> > > 375 nop > >> > > > >> > > > >> > > while the code in start.s is: > >> > > > >> > > zerobss: > >> > > std %g0,[%g2] > >> > > add %g2,8,%g2 > >> > > cmp %g2,%g3 > >> > > bleu,a zerobss > >> > > nop > >> > > > >> > > --------------------- > >> > > > >> > > Can someone please tell me why gdb is not going back to the main > file > >> > > smpschededf02/init.c? Is it because we keep running start.s during > the > >> > > entire time of execution? > >> > > >> > zerobss: function is not infinite, it just loops for many thousands > (millions) iterations while it clears the bss segment. SIngle-stepping though > zerobss: will obviously take a VERY long time, so put a breakpoint on > somewhere after it has been called. > >> > > >> > > >> > > And how do I run gdb while going through > >> > > every instruction that init.c processes without getting stuck in an > >> > > infinite loop like this. I set up a breakpoint at Init and > everythings > >> > > work fine but I am stilling missing the commands that were executed > >> > > before Init.c was called. How do I see those? > >> > > > >> > > Also, If I use step with breakpoint at Init, it again goes into an > >> > > infinite loop inside apbuart_polled.c with the following commands: > >> > > > >> > > 20 while ( (regs->status & APBUART_STATUS_TE) == 0 ) { > >> > > (gdb) > >> > > 22 __asm__ volatile ("nop"::); __asm__ volatile ("nop"::); > >> > > (gdb) > >> > > 23 __asm__ volatile ("nop"::); __asm__ volatile ("nop"::); > >> > > (gdb) > >> > > 24 __asm__ volatile ("nop"::); __asm__ volatile ("nop"::); > >> > > (gdb) > >> > > 25 __asm__ volatile ("nop"::); __asm__ volatile ("nop"::); > >> > > > >> > > Why is it running into an infinite loop?(If I use nexti, it does > not > >> > > run into an infinite loop as next does get inside functions, and > Init > >> > > finishes successfully). > >> > > >> > The loop is not infinite, it just loops while waiting for the UART > transmitter to send out a character. nexti puts a breakpoint after the loop, > that is why it finishes. > >> > > >> > Jiri. > >> > > >> > > >> > > > >> > > Thanks, > >> > > Richi. > >> > > > >> > > On Tue, May 26, 2020 at 12:44 AM Jiri Gaisler <j...@gaisler.se > <mailto:j...@gaisler.se>> wrote: > >> > >> > >> > >> On 5/25/20 4:30 PM, Richi Dubey wrote: > >> > >>> Hii everyone, > >> > >>> > >> > >>> When I am executing smpschededf02.exe on my leon3 bsp running on > >> > >>> sparc5 with sparc-rtems5-sis with -m 4 -leon3 option, it fails > to > >> > >>> execute properly. > >> > >>> > >> > >>> I have built leon3 with --enable-smp option and I am guessing the > >> > >>> execution fails because I don not see any output of the test and > I can > >> > >>> only see the following output: > >> > >>> --------------------------------------------- > >> > >>> ~/quick-start/rtems/5/bin$ ./sparc-rtems5-sis -leon3 -m 4 > >> > >>> > ~/quick-start/build/leon3/sparc-rtems5/c/leon3/testsuites/smptests/smpschededf02.exe > >> > >>> > >> > >>> SIS - SPARC/RISCV instruction simulator 2.21, copyright Jiri > Gaisler 2019 > >> > >>> Bug-reports to j...@gaisler.se <mailto:j...@gaisler.se> > >> > >>> > >> > >>> LEON3 emulation enabled, 4 cpus online, delta 50 clocks > >> > >>> > >> > >>> Loaded > /home/richi/quick-start/build/leon3/sparc-rtems5/c/leon3/testsuites/smptests/smpschededf02.exe, > >> > >>> entry 0x40000000 > >> > >>> cpu0> run > >> > >>> > >> > >>> > >> > >>> *** BEGIN OF TEST SMPSCHEDEDF 2 *** > >> > >>> *** TEST VERSION: 5.0.0.20a8361de4724658112ecd33c28fae82a15919f8 > >> > >>> *** TEST STATE: EXPECTED_PASS > >> > >>> *** TEST BUILD: RTEMS_NETWORKING RTEMS_POSIX_API RTEMS_SMP > >> > >>> *** TEST TOOLS: 7.5.0 20191114 (RTEMS 5, RSB 5 (0b7e87143b76), > Newlib fbaa096) > >> > >>> > >> > >>> *** END OF TEST SMPSCHEDEDF 2 *** > >> > >>> > >> > >>> cpu 1 in error mode (tt = 0x80) > >> > >>> 3491850 40016360: 91d02000 ta 0x0 > >> > >>> ------------------------------------------------------- > >> > >> Looks good to me, test passed OK and processor is halted by RTEMS. > >> > >> > >> > >> > >> > >>> On running the program with gdb with extended-remote and > debugging > >> > >>> with sis, I am encountering the following error: > >> > >>> > >> > >>> ---------------------- > >> > >>> (gdb) target extended-remote localhost:1234 > >> > >>> Remote debugging using localhost:1234 > >> > >>> 0x00000000 in ?? () > >> > >>> (gdb) > >> > >>> ------------------------ > >> > >> This is indeed how you start remote debugging, but then you also > have to do: > >> > >> > >> > >> load > >> > >> > >> > >> run > >> > >> > >> > >> Then the program should run as expected ... > >> > >> > >> > >> > >> > >> Jiri. > >> > >> > >> > >> > >> > >> _______________________________________________ > >> > >> devel mailing list > >> > >> devel@rtems.org <mailto:devel@rtems.org> > >> > >> http://lists.rtems.org/mailman/listinfo/devel > >> > > > > > _______________________________________________ > > devel mailing list > > devel@rtems.org <mailto:devel@rtems.org> > > http://lists.rtems.org/mailman/listinfo/devel >
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