Messages in this thread | | | Date | Tue, 5 Apr 2022 19:21:04 +0300 | Subject | Re: [PATCH v13 01/16] perf record: Introduce thread affinity and mmap masks | From | "Bayduraev, Alexey V" <> |
| |
On 05.04.2022 1:25, Ian Rogers wrote: > On Mon, Jan 17, 2022 at 10:38 AM Alexey Bayduraev > <alexey.v.bayduraev@linux.intel.com> wrote: >> >> Introduce affinity and mmap thread masks. Thread affinity mask
<SNIP>
> > In per-thread mode it is possible that cpus is the dummy CPU map here. > This means that the cpu below has the value -1 and setting bit -1 > actually has the effect of setting bit 63. Here is a reproduction > based on the acme/perf/core branch: > > ``` > $ make STATIC=1 DEBUG=1 EXTRA_CFLAGS='-fno-omit-frame-pointer > -fsanitize=undefined -fno-sanitize-recover' > $ perf record -o /tmp/perf.data --per-thread true > tools/include/asm-generic/bitops/atomic.h:10:36: runtime error: shift > exponent -1 is negative > $ UBSAN_OPTIONS=abort_on_error=1 gdb --args perf record -o > /tmp/perf.data --per-thread true > (gdb) r > tools/include/asm-generic/bitops/atomic.h:10:36: runtime error: shift > exponent -1 is negative > (gdb) bt > #0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:49 > #1 0x00007ffff71d2546 in __GI_abort () at abort.c:79 > #2 0x00007ffff640db9f in __sanitizer::Abort () at > ../../../../src/libsanitizer/sanitizer_common/sanitizer_posix_libcdep.cpp:151 > #3 0x00007ffff6418efc in __sanitizer::Die () at > ../../../../src/libsanitizer/sanitizer_common/sanitizer_termination.cpp:58 > #4 0x00007ffff63fd99e in > __ubsan::__ubsan_handle_shift_out_of_bounds_abort (Data=<optimized > out>, LHS=<optimized out>, > RHS=<optimized out>) at > ../../../../src/libsanitizer/ubsan/ubsan_handlers.cpp:378 > #5 0x0000555555c54405 in set_bit (nr=-1, addr=0x555556ecd0a0) > at tools/include/asm-generic/bitops/atomic.h:10 > #6 0x0000555555c6ddaf in record__mmap_cpu_mask_init > (mask=0x555556ecd070, cpus=0x555556ecd050) at builtin-record.c:3333 > #7 0x0000555555c7044c in record__init_thread_default_masks > (rec=0x55555681b100 <record>, cpus=0x555556ecd050) at > builtin-record.c:3668 > #8 0x0000555555c705b3 in record__init_thread_masks > (rec=0x55555681b100 <record>) at builtin-record.c:3681 > #9 0x0000555555c7297a in cmd_record (argc=1, argv=0x7fffffffdcc0) at > builtin-record.c:3976 > #10 0x0000555555e06d41 in run_builtin (p=0x555556827538 > <commands+216>, argc=5, argv=0x7fffffffdcc0) at perf.c:313 > #11 0x0000555555e07253 in handle_internal_command (argc=5, > argv=0x7fffffffdcc0) at perf.c:365 > #12 0x0000555555e07508 in run_argv (argcp=0x7fffffffdb0c, > argv=0x7fffffffdb00) at perf.c:409 > #13 0x0000555555e07b32 in main (argc=5, argv=0x7fffffffdcc0) at perf.c:539 > ``` > > Not setting the mask->bits if the cpu map is dummy causes no data to > be written. Setting mask->bits 0 causes a segv. Setting bit 63 works > but feels like there are more invariants broken in the code. > > Here is a not good workaround patch: > > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c > index ba74fab02e62..62727b676f98 100644 > --- a/tools/perf/builtin-record.c > +++ b/tools/perf/builtin-record.c > @@ -3329,6 +3329,11 @@ static void record__mmap_cpu_mask_init(struct > mmap_cpu_mask *mask, struct perf_c > { > int c; > > + if (cpu_map__is_dummy(cpus)) { > + set_bit(63, mask->bits); > + return; > + } > + > for (c = 0; c < cpus->nr; c++) > set_bit(cpus->map[c].cpu, mask->bits); > } > > Alexey, what should the expected behavior be with per-thread mmaps? > > Thanks, > Ian
Thanks a lot,
In case of per-thread mmaps we should initialize thread_data[0]->maps[i] by evlist->mmap[i]. Looks like this was missed by this patchset.
Your patch works, because it triggers test_bit() in record__thread_data_init_maps() and thread_data maps get correctly initialized.
However, it's better to ignore thread_data->masks in record__mmap_cpu_mask_init() and setup thread_data maps explicitly for per-thread case.
Also, to prevent more runtime crashes, --per-thread and --threads options should be mutually exclusive.
I will prepare a fix for this issue soon.
Regards, Alexey
> >> +static void record__free_thread_masks(struct record *rec, int nr_threads) >> +{ >> + int t; >> + >> + if (rec->thread_masks) >> + for (t = 0; t < nr_threads; t++) >> + record__thread_mask_free(&rec->thread_masks[t]); >> + >> + zfree(&rec->thread_masks); >> +} >> + >> +static int record__alloc_thread_masks(struct record *rec, int nr_threads, int nr_bits) >> +{ >> + int t, ret; >> + >> + rec->thread_masks = zalloc(nr_threads * sizeof(*(rec->thread_masks))); >> + if (!rec->thread_masks) { >> + pr_err("Failed to allocate thread masks\n"); >> + return -ENOMEM; >> + } >> + >> + for (t = 0; t < nr_threads; t++) { >> + ret = record__thread_mask_alloc(&rec->thread_masks[t], nr_bits); >> + if (ret) { >> + pr_err("Failed to allocate thread masks[%d]\n", t); >> + goto out_free; >> + } >> + } >> + >> + return 0; >> + >> +out_free: >> + record__free_thread_masks(rec, nr_threads); >> + >> + return ret; >> +} >> + >> +static int record__init_thread_default_masks(struct record *rec, struct perf_cpu_map *cpus) >> +{ >> + int ret; >> + >> + ret = record__alloc_thread_masks(rec, 1, cpu__max_cpu().cpu); >> + if (ret) >> + return ret; >> + >> + record__mmap_cpu_mask_init(&rec->thread_masks->maps, cpus); >> + >> + rec->nr_threads = 1; >> + >> + return 0; >> +} >> + >> +static int record__init_thread_masks(struct record *rec) >> +{ >> + struct perf_cpu_map *cpus = rec->evlist->core.cpus; >> + >> + return record__init_thread_default_masks(rec, cpus); >> +} >> + >> int cmd_record(int argc, const char **argv) >> { >> int err; >> @@ -2948,6 +3063,12 @@ int cmd_record(int argc, const char **argv) >> goto out; >> } >> >> + err = record__init_thread_masks(rec); >> + if (err) { >> + pr_err("Failed to initialize parallel data streaming masks\n"); >> + goto out; >> + } >> + >> if (rec->opts.nr_cblocks > nr_cblocks_max) >> rec->opts.nr_cblocks = nr_cblocks_max; >> pr_debug("nr_cblocks: %d\n", rec->opts.nr_cblocks); >> @@ -2966,6 +3087,8 @@ int cmd_record(int argc, const char **argv) >> symbol__exit(); >> auxtrace_record__free(rec->itr); >> out_opts: >> + record__free_thread_masks(rec, rec->nr_threads); >> + rec->nr_threads = 0; >> evlist__close_control(rec->opts.ctl_fd, rec->opts.ctl_fd_ack, &rec->opts.ctl_fd_close); >> return err; >> } >> -- >> 2.19.0 >>
| |