[PATCH 4/4] perf tools: Retry mapping buffers readonly on EACCES

[Robert Richter]

From: Robert Richter <robert.rich...@calxeda.com>

Persistent event buffers may only be mmapped readonly. Thus, retry
mapping it readonly if mmap returns EACCES after trying to mmap
writable.

Signed-off-by: Robert Richter <robert.rich...@calxeda.com>
---
 tools/perf/builtin-record.c | 7 ++++++-
 tools/perf/builtin-top.c    | 8 ++++++--
 tools/perf/perf.h           | 1 +
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index cdf58ec..916776d 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -255,7 +255,12 @@ try_again:
                goto out;
        }
 
-       if (perf_evlist__mmap(evlist, opts->mmap_pages, false) < 0) {
+try_again2:
+       if (perf_evlist__mmap(evlist, opts->mmap_pages, opts->mmap_ro) < 0) {
+               if (!opts->mmap_ro && errno == EACCES) {
+                       opts->mmap_ro = true;
+                       goto try_again2;
+               }
                if (errno == EPERM) {
                        pr_err("Permission error mapping pages.\n"
                               "Consider increasing "
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 67bdb9f..2a5757d 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -899,8 +899,12 @@ try_again:
                        goto out_err;
                }
        }
-
-       if (perf_evlist__mmap(evlist, opts->mmap_pages, false) < 0) {
+try_again2:
+       if (perf_evlist__mmap(evlist, opts->mmap_pages, opts->mmap_ro) < 0) {
+               if (!opts->mmap_ro && errno == EACCES) {
+                       opts->mmap_ro = true;
+                       goto try_again2;
+               }
                ui__error("Failed to mmap with %d (%s)\n",
                            errno, strerror(errno));
                goto out_err;
diff --git a/tools/perf/perf.h b/tools/perf/perf.h
index 32bd102..41acea3 100644
--- a/tools/perf/perf.h
+++ b/tools/perf/perf.h
@@ -221,6 +221,7 @@ struct perf_record_opts {
        bool         sample_weight;
        bool         sample_time;
        bool         period;
+       bool         mmap_ro;
        unsigned int freq;
        unsigned int mmap_pages;
        unsigned int user_freq;
-- 
1.8.1.1

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