From: Jiri Olsa <[email protected]> [ 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: [email protected] Signed-off-by: Jiri Olsa <[email protected]> Tested-by: Arnaldo Carvalho de Melo <[email protected]> Cc: Alexander Shishkin <[email protected]> Cc: David Ahern <[email protected]> Cc: Don Zickus <[email protected]> Cc: Joe Mario <[email protected]> Cc: Namhyung Kim <[email protected]> Cc: Peter Zijlstra <[email protected]> Fixes: f1c5fd4d0bb9 ("perf c2c report: Add TUI cacheline browser") Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Arnaldo Carvalho de Melo <[email protected]> Signed-off-by: Sasha Levin <[email protected]> --- 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 3479a1bc7caa..fb76423022e8 100644 --- a/tools/perf/builtin-c2c.c +++ b/tools/perf/builtin-c2c.c @@ -2229,6 +2229,9 @@ static int perf_c2c__browse_cacheline(struct hist_entry *he) " s Togle full lenght 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; -- 2.17.1
