From: Jiri Olsa jolsa@kernel.org
[ Upstream commit 73978332572ccf5e364c31e9a70ba953f8202b46 ]
'perf c2c' scans read/write accesses and tries to find false sharing cases, so when the events it wants were not asked for or ended up not taking place, we get no histograms.
So do not try to display entry details if there's not any. Currently this ends up in crash:
$ perf c2c report # then press 'd' perf: Segmentation fault $
Committer testing:
Before:
Record a perf.data file without events of interest to 'perf c2c report', then call it and press 'd':
# perf record sleep 1 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.001 MB perf.data (6 samples) ] # perf c2c report perf: Segmentation fault -------- backtrace -------- perf[0x5b1d2a] /lib64/libc.so.6(+0x346df)[0x7fcb566e36df] perf[0x46fcae] perf[0x4a9f1e] perf[0x4aa220] perf(main+0x301)[0x42c561] /lib64/libc.so.6(__libc_start_main+0xe9)[0x7fcb566cff29] perf(_start+0x29)[0x42c999] #
After the patch the segfault doesn't take place, a follow up patch to tell the user why nothing changes when 'd' is pressed would be good.
Reported-by: rodia@autistici.org Signed-off-by: Jiri Olsa jolsa@kernel.org Tested-by: Arnaldo Carvalho de Melo acme@redhat.com Cc: Alexander Shishkin alexander.shishkin@linux.intel.com Cc: David Ahern dsahern@gmail.com Cc: Don Zickus dzickus@redhat.com Cc: Joe Mario jmario@redhat.com Cc: Namhyung Kim namhyung@kernel.org Cc: Peter Zijlstra peterz@infradead.org Fixes: f1c5fd4d0bb9 ("perf c2c report: Add TUI cacheline browser") Link: http://lkml.kernel.org/r/20180724062008.26126-1-jolsa@kernel.org Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- tools/perf/builtin-c2c.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/tools/perf/builtin-c2c.c b/tools/perf/builtin-c2c.c index 6a8738f7ead3..eab66e3b0a19 100644 --- a/tools/perf/builtin-c2c.c +++ b/tools/perf/builtin-c2c.c @@ -2349,6 +2349,9 @@ static int perf_c2c__browse_cacheline(struct hist_entry *he) " s Toggle full length of symbol and source line columns \n" " q Return back to cacheline list \n";
+ if (!he) + return 0; + /* Display compact version first. */ c2c.symbol_full = false;