[PATCH 40/46] perf tools: Record fd into perf_mmap

Wang Nan
2016-02-26T09:34:48Z

Add a fd field into perf_mmap so perf can backtrack the fd from mmap.
This feature will be used to toggle overwrite ring buffers.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Signed-off-by: He Kuang <hekuang@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
---
tools/perf/util/evlist.c | 15 +++++++++++++--
tools/perf/util/evlist.h | 1 +
2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 7877061..c72905d 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -868,6 +868,7 @@ static void __perf_evlist__munmap(struct perf_evlist *evlist, int idx)
if (evlist->mmap[idx].base != NULL) {
munmap(evlist->mmap[idx].base, evlist->mmap_len);
evlist->mmap[idx].base = NULL;
+ evlist->mmap[idx].fd = -1;
atomic_set(&evlist->mmap[idx].refcnt, 0);
}
auxtrace_mmap__munmap(&evlist->mmap[idx].auxtrace_mmap);
@@ -903,7 +904,7 @@ void perf_evlist__munmap(struct perf_evlist *evlist)

static int perf_evlist__alloc_mmap(struct perf_evlist *evlist)
{
- int total_mmaps;
+ int total_mmaps, i;

evlist->nr_mmaps = cpu_map__nr(evlist->cpus);
if (cpu_map__empty(evlist->cpus))
@@ -914,7 +915,12 @@ static int perf_evlist__alloc_mmap(struct perf_evlist *evlist)
return -EINVAL;

evlist->mmap = zalloc(total_mmaps * sizeof(struct perf_mmap));
- return evlist->mmap != NULL ? 0 : -ENOMEM;
+ if (!evlist->mmap)
+ return -ENOMEM;
+
+ for (i = 0; i < total_mmaps; i++)
+ evlist->mmap[i].fd = -1;
+ return 0;
}

struct mmap_params {
@@ -934,6 +940,10 @@ static int __perf_evlist__mmap(struct perf_evlist *evlist, int idx,
if (!perf_evlist__channel_check(evlist, channel, RDONLY))
prot |= PROT_WRITE;

+ if (evlist->mmap[idx].fd >= 0) {
+ pr_err("idx %d already mapped\n", idx);
+ return -1;
+ }
/*
* The last one will be done at perf_evlist__mmap_consume(), so that we
* make sure we don't prevent tools from consuming every last event in
@@ -958,6 +968,7 @@ static int __perf_evlist__mmap(struct perf_evlist *evlist, int idx,
evlist->mmap[idx].base = NULL;
return -1;
}
+ evlist->mmap[idx].fd = fd;

if (auxtrace_mmap__mmap(&evlist->mmap[idx].auxtrace_mmap,
&mp->auxtrace_mp, evlist->mmap[idx].base, fd))
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 321224c..bc6d787 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -35,6 +35,7 @@ enum perf_evlist_mmap_flag {
struct perf_mmap {
void *base;
int mask;
+ int fd;
atomic_t refcnt;
u64 prev;
struct auxtrace_mmap auxtrace_mmap;
--
1.8.3.4