Reading from a overwrite ring buffer is unrelible. perf_evlist__channel_toggle_paused() should be called before reading from them.
Toggel overwrite_evt_paused director after receiving done or switch output. Signed-off-by: Wang Nan <[email protected]> Signed-off-by: He Kuang <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: Masami Hiramatsu <[email protected]> Cc: Namhyung Kim <[email protected]> Cc: Zefan Li <[email protected]> Cc: [email protected] --- tools/perf/builtin-record.c | 79 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 79 insertions(+) diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index a069f75..8d247cf 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -40,6 +40,11 @@ #include <sys/mman.h> #include <asm/bug.h> +enum overwrite_evt_state { + OVERWRITE_EVT_RUNNING, + OVERWRITE_EVT_DATA_PENDING, + OVERWRITE_EVT_EMPTY, +}; struct record { struct perf_tool tool; @@ -58,6 +63,7 @@ struct record { bool buildid_all; bool timestamp_filename; bool switch_output; + enum overwrite_evt_state overwrite_evt_state; unsigned long long samples; }; @@ -389,6 +395,7 @@ try_again: session->evlist = evlist; perf_session__set_id_hdr_size(session); + rec->overwrite_evt_state = OVERWRITE_EVT_RUNNING; out: return rc; } @@ -469,6 +476,52 @@ static struct perf_event_header finished_round_event = { .type = PERF_RECORD_FINISHED_ROUND, }; +static void +record__toggle_overwrite_evsels(struct record *rec, + enum overwrite_evt_state state) +{ + struct perf_evlist *evlist = rec->evlist; + enum overwrite_evt_state old_state = rec->overwrite_evt_state; + enum action { + NONE, + PAUSE, + RESUME, + } action = NONE; + int ch, nr_channels; + + switch (old_state) { + case OVERWRITE_EVT_RUNNING: + if (state != OVERWRITE_EVT_RUNNING) + action = PAUSE; + break; + case OVERWRITE_EVT_DATA_PENDING: + if (state == OVERWRITE_EVT_RUNNING) + action = RESUME; + break; + case OVERWRITE_EVT_EMPTY: + if (state == OVERWRITE_EVT_RUNNING) + action = RESUME; + if (state == OVERWRITE_EVT_DATA_PENDING) + state = OVERWRITE_EVT_EMPTY; + break; + default: + WARN_ONCE(1, "Shouldn't get there\n"); + } + + rec->overwrite_evt_state = state; + + if (action == NONE) + return; + + nr_channels = perf_evlist__channel_nr(evlist); + for (ch = 0; ch < nr_channels; ch++) { + if (!perf_evlist__channel_check(evlist, ch, RDONLY)) + continue; + perf_evlist__channel_toggle_paused(evlist, ch, + action == PAUSE); + } +} + static bool record__mmap_should_read(struct record *rec, int idx) { int channel = -1; @@ -513,6 +566,8 @@ static int record__mmap_read_all(struct record *rec) if (bytes_written != rec->bytes_written) rc = record__write(rec, &finished_round_event, sizeof(finished_round_event)); + if (rec->overwrite_evt_state == OVERWRITE_EVT_DATA_PENDING) + record__toggle_overwrite_evsels(rec, OVERWRITE_EVT_EMPTY); out: return rc; } @@ -872,6 +927,17 @@ static int __cmd_record(struct record *rec, int argc, const char **argv) for (;;) { unsigned long long hits = rec->samples; + /* + * rec->overwrite_evt_state is possible to be + * OVERWRITE_EVT_EMPTY here: when done == true and + * hits != rec->samples after previous reading. + * + * record__toggle_overwrite_evsels ensure we never + * convert OVERWRITE_EVT_EMPTY to OVERWRITE_EVT_DATA_PENDING. + */ + if (switch_output_started || done || draining) + record__toggle_overwrite_evsels(rec, OVERWRITE_EVT_DATA_PENDING); + if (record__mmap_read_all(rec) < 0) { auxtrace_snapshot_disable(); err = -1; @@ -890,7 +956,20 @@ static int __cmd_record(struct record *rec, int argc, const char **argv) } if (switch_output_started) { + /* + * SIGUSR2 raise after or during record__mmap_read_all(). + * continue to read again. + */ + if (rec->overwrite_evt_state == OVERWRITE_EVT_RUNNING) + continue; + switch_output_started = 0; + /* + * Reenable events in overwrite ring buffer after + * record__mmap_read_all(): we should have collected + * data from it. + */ + record__toggle_overwrite_evsels(rec, OVERWRITE_EVT_RUNNING); if (!quiet) fprintf(stderr, "[ perf record: dump data: Woken up %ld times ]\n", -- 1.8.3.4
