Commit 73978332 authored by Jiri Olsa's avatar Jiri Olsa Committed by Arnaldo Carvalho de Melo

perf c2c report: Fix crash for empty browser

'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: default avatarJiri Olsa <jolsa@kernel.org>
Tested-by: default avatarArnaldo 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: f1c5fd4d ("perf c2c report: Add TUI cacheline browser")
Link: http://lkml.kernel.org/r/20180724062008.26126-1-jolsa@kernel.orgSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent aa90f9f9
...@@ -2349,6 +2349,9 @@ static int perf_c2c__browse_cacheline(struct hist_entry *he) ...@@ -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" " s Toggle full length of symbol and source line columns \n"
" q Return back to cacheline list \n"; " q Return back to cacheline list \n";
if (!he)
return 0;
/* Display compact version first. */ /* Display compact version first. */
c2c.symbol_full = false; c2c.symbol_full = false;
......
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