On 12.08.21 г. 3:55, Steven Rostedt wrote:
From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx> The 'hist' triggers expect that all variables are unique. If two synthetic events are created, it is possible that they will use the same variable names, and this can break the logic for synthetic events. Add a random number to the argument names that will help prevent that from happening. There's no guarantee that there wont be collisions, but the chances of that happening is 1 in 65535. If this is a problem, we could possibly look for variables that are already in use. Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> --- src/tracefs-hist.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/src/tracefs-hist.c b/src/tracefs-hist.c index 7f9cf3820611..8783ef4364bd 100644 --- a/src/tracefs-hist.c +++ b/src/tracefs-hist.c @@ -13,6 +13,8 @@ #include <errno.h> #include <fcntl.h> #include <limits.h> +#include <time.h> +#include <sys/types.h>#include "tracefs.h"#include "tracefs-local.h" @@ -558,6 +560,7 @@ struct tracefs_synth { unsigned int end_parens; unsigned int end_state; int *start_type; + char arg_name[16]; int arg_cnt; };@@ -957,7 +960,15 @@ static char *new_arg(struct tracefs_synth *synth)char *arg; int ret;- ret = asprintf(&arg, "__arg__%d", cnt);+ /* Create a unique argument name */ + if (!synth->arg_name[0]) { + srand(time(NULL));
Nit: Have in mind that time(NULL) has 1 second resolution. Fast consecutive calls (within a second) of this function can generate identical random numbers.
This can be mitigated if we do something like this: struct timeval now; gettimeofday(&now, NULL); srand(now.tv_usec); -- Yordan
+ ret = rand() + gettid(); + /* Truncate so that ret is at most 65535 (total 13 bytes) */ + ret &= (1 << 16) - 1; + sprintf(synth->arg_name, "__arg_%d_", ret); + } + ret = asprintf(&arg, "%s%d", synth->arg_name, cnt); if (ret < 0) return NULL;
|