The offending commit removed mmap_per_thread(), which did not consider
the different set-output rules for per-thread mmaps i.e. in the per-thread
case set-output is used for file descriptors of the same thread not the
same cpu.

This was not immediately noticed because it only happens with
multi-threaded targets and we do not have a test for that yet.

Reinstate mmap_per_thread() expanding it to cover also system-wide per-cpu
events i.e. to continue to allow the mixing of per-thread and per-cpu
mmaps.

Debug messages (with -vv) show the file descriptors that are opened with
sys_perf_event_open. New debug messages are added (needs -vvv) that show
also which file descriptors are mmapped and which are redirected with
set-output.

In the per-cpu case (cpu != -1) file descriptors for the same CPU are
set-output to the first file descriptor for that CPU.

In the per-thread case (cpu == -1) file descriptors for the same thread are
set-output to the first file descriptor for that thread.

Example (process 17489 has 2 threads):

 Before (but with new debug prints):

   $ perf record --no-bpf-event -vvv --per-thread -p 17489
   <SNIP>
   sys_perf_event_open: pid 17489  cpu -1  group_fd -1  flags 0x8 = 5
   sys_perf_event_open: pid 17490  cpu -1  group_fd -1  flags 0x8 = 6
   <SNIP>
   libperf: idx 0: mmapping fd 5
   libperf: idx 0: set output fd 6 -> 5
   failed to mmap with 22 (Invalid argument)

 After:

   $ perf record --no-bpf-event -vvv --per-thread -p 17489
   <SNIP>
   sys_perf_event_open: pid 17489  cpu -1  group_fd -1  flags 0x8 = 5
   sys_perf_event_open: pid 17490  cpu -1  group_fd -1  flags 0x8 = 6
   <SNIP>
   libperf: mmap_per_thread: nr cpu values (may include -1) 1 nr threads 2
   libperf: idx 0: mmapping fd 5
   libperf: idx 1: mmapping fd 6
   <SNIP>
   [ perf record: Woken up 2 times to write data ]
   [ perf record: Captured and wrote 0.018 MB perf.data (15 samples) ]

Per-cpu example (process 20341 has 2 threads, same as above):

   $ perf record --no-bpf-event -vvv -p 20341
   <SNIP>
   sys_perf_event_open: pid 20341  cpu 0  group_fd -1  flags 0x8 = 5
   sys_perf_event_open: pid 20342  cpu 0  group_fd -1  flags 0x8 = 6
   sys_perf_event_open: pid 20341  cpu 1  group_fd -1  flags 0x8 = 7
   sys_perf_event_open: pid 20342  cpu 1  group_fd -1  flags 0x8 = 8
   sys_perf_event_open: pid 20341  cpu 2  group_fd -1  flags 0x8 = 9
   sys_perf_event_open: pid 20342  cpu 2  group_fd -1  flags 0x8 = 10
   sys_perf_event_open: pid 20341  cpu 3  group_fd -1  flags 0x8 = 11
   sys_perf_event_open: pid 20342  cpu 3  group_fd -1  flags 0x8 = 12
   sys_perf_event_open: pid 20341  cpu 4  group_fd -1  flags 0x8 = 13
   sys_perf_event_open: pid 20342  cpu 4  group_fd -1  flags 0x8 = 14
   sys_perf_event_open: pid 20341  cpu 5  group_fd -1  flags 0x8 = 15
   sys_perf_event_open: pid 20342  cpu 5  group_fd -1  flags 0x8 = 16
   sys_perf_event_open: pid 20341  cpu 6  group_fd -1  flags 0x8 = 17
   sys_perf_event_open: pid 20342  cpu 6  group_fd -1  flags 0x8 = 18
   sys_perf_event_open: pid 20341  cpu 7  group_fd -1  flags 0x8 = 19
   sys_perf_event_open: pid 20342  cpu 7  group_fd -1  flags 0x8 = 20
   <SNIP>
   libperf: mmap_per_cpu: nr cpu values 8 nr threads 2
   libperf: idx 0: mmapping fd 5
   libperf: idx 0: set output fd 6 -> 5
   libperf: idx 1: mmapping fd 7
   libperf: idx 1: set output fd 8 -> 7
   libperf: idx 2: mmapping fd 9
   libperf: idx 2: set output fd 10 -> 9
   libperf: idx 3: mmapping fd 11
   libperf: idx 3: set output fd 12 -> 11
   libperf: idx 4: mmapping fd 13
   libperf: idx 4: set output fd 14 -> 13
   libperf: idx 5: mmapping fd 15
   libperf: idx 5: set output fd 16 -> 15
   libperf: idx 6: mmapping fd 17
   libperf: idx 6: set output fd 18 -> 17
   libperf: idx 7: mmapping fd 19
   libperf: idx 7: set output fd 20 -> 19
   <SNIP>
   [ perf record: Woken up 7 times to write data ]
   [ perf record: Captured and wrote 0.020 MB perf.data (17 samples) ]

Fixes: ae4f8ae1 ("libperf evlist: Allow mixing per-thread and per-cpu mmaps")
Reported-by: Tomáš Trnka <trnka@scm.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=216441Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220905114209.8389-1-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>