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timeval: Take a backtrace on each SIGALRM.

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With this patch, timeval will take a backtrace with each SIGALRM
allowing it to retrieve a profiling snapshot instantly.  This will
be useful in future patches when backtraces are logged.

Signed-off-by: Ethan Jackson <ethan@nicira.com>
This commit is contained in:
Ethan Jackson
2012-10-17 16:43:38 -07:00
parent d2bcb6bb73
commit fdce775cc5
1 changed files with 26 additions and 42 deletions
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68
lib/timeval.c
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@@ -75,9 +75,8 @@ struct trace {
};
#define MAX_TRACES 50
static struct unixctl_conn *backtrace_conn = NULL;
static struct trace *traces = NULL;
static size_t n_traces = 0;
static struct trace traces[MAX_TRACES];
static size_t trace_head = 0;
static void set_up_timer(void);
static void set_up_signal(int flags);
@@ -91,7 +90,6 @@ static struct rusage *get_recent_rusage(void);
static void refresh_rusage(void);
static void timespec_add(struct timespec *sum,
const struct timespec *a, const struct timespec *b);
static void trace_run(void);
static unixctl_cb_func backtrace_cb;
/* Initializes the timetracking module, if not already initialized. */
@@ -100,16 +98,13 @@ time_init(void)
{
static bool inited;
/* The best place to do this is probably a timeval_run() function.
* However, none exists and this function is usually so fast that doing it
* here seems fine for now. */
trace_run();
if (inited) {
return;
}
inited = true;
memset(traces, 0, sizeof traces);
if (HAVE_EXECINFO_H && CACHE_TIME) {
unixctl_command_register("backtrace", "", 0, 0, backtrace_cb, NULL);
}
@@ -377,7 +372,7 @@ time_poll(struct pollfd *pollfds, int n_pollfds, long long int timeout_when,
break;
}
if (!blocked && CACHE_TIME && !backtrace_conn) {
if (!blocked && CACHE_TIME) {
block_sigalrm(&oldsigs);
blocked = true;
}
@@ -398,10 +393,12 @@ sigalrm_handler(int sig_nr OVS_UNUSED)
monotonic_tick = true;
#if HAVE_EXECINFO_H
if (backtrace_conn && n_traces < MAX_TRACES) {
struct trace *trace = &traces[n_traces++];
if (CACHE_TIME) {
struct trace *trace = &traces[trace_head];
trace->n_frames = backtrace(trace->backtrace,
ARRAY_SIZE(trace->backtrace));
trace_head = (trace_head + 1) % MAX_TRACES;
}
#endif
}
@@ -581,42 +578,38 @@ get_cpu_usage(void)
}
static void
trace_run(void)
format_backtraces(struct ds *ds)
{
time_init();
#if HAVE_EXECINFO_H
if (backtrace_conn && n_traces >= MAX_TRACES) {
struct unixctl_conn *reply_conn = backtrace_conn;
struct ds ds = DS_EMPTY_INITIALIZER;
if (CACHE_TIME) {
sigset_t oldsigs;
size_t i;
block_sigalrm(&oldsigs);
for (i = 0; i < n_traces; i++) {
for (i = 0; i < MAX_TRACES; i++) {
struct trace *trace = &traces[i];
char **frame_strs;
size_t j;
if (!trace->n_frames) {
continue;
}
frame_strs = backtrace_symbols(trace->backtrace, trace->n_frames);
ds_put_format(&ds, "Backtrace %zu\n", i + 1);
ds_put_format(ds, "Backtrace %zu\n", i + 1);
for (j = 0; j < trace->n_frames; j++) {
ds_put_format(&ds, "%s\n", frame_strs[j]);
ds_put_format(ds, "%s\n", frame_strs[j]);
}
ds_put_cstr(&ds, "\n");
ds_put_cstr(ds, "\n");
free(frame_strs);
}
free(traces);
traces = NULL;
n_traces = 0;
backtrace_conn = NULL;
ds_chomp(ds, '\n');
unblock_sigalrm(&oldsigs);
unixctl_command_reply(reply_conn, ds_cstr(&ds));
ds_destroy(&ds);
}
#endif
}
@@ -664,21 +657,12 @@ backtrace_cb(struct unixctl_conn *conn,
int argc OVS_UNUSED, const char *argv[] OVS_UNUSED,
void *aux OVS_UNUSED)
{
sigset_t oldsigs;
struct ds ds = DS_EMPTY_INITIALIZER;
assert(HAVE_EXECINFO_H && CACHE_TIME);
if (backtrace_conn) {
unixctl_command_reply_error(conn, "In Use");
return;
}
assert(!traces);
block_sigalrm(&oldsigs);
backtrace_conn = conn;
traces = xmalloc(MAX_TRACES * sizeof *traces);
n_traces = 0;
unblock_sigalrm(&oldsigs);
format_backtraces(&ds);
unixctl_command_reply(conn, ds_cstr(&ds));
ds_destroy(&ds);
}
void