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library: ensure thread safety for all static variables

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Even though we we had to abandon the master branch top
multi-thread effort and even though the newlib version
of a multi-threaded top provides no real benefit, that
whole exercise was not wasted. Rather, it has revealed
some deficiencies in our library which this addresses.

If two or more threads in the same address space tried
to access the same api simultaneously, there is a good
chance some function-local static variables will yield
some of those renowned unpredictable results. So, this
patch protects them with the '__thread' storage class.

Reference(s):
https://www.freelists.org/post/procps/a-few-more-patches,7

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner
2021-09-28 00:00:00 -05:00
committed by Craig Small
parent 69978e3650
commit 23cfb71366
10 changed files with 28 additions and 28 deletions
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26
proc/readproc.c
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@@ -965,7 +965,7 @@ static int fill_environ_cvt (const char *directory, proc_t *restrict p) {
// tracking all names already seen thus avoiding the overhead of repeating
// malloc() and free() calls.
static char *lxc_containers (const char *path) {
static struct utlbuf_s ub = { NULL, 0 }; // util buffer for whole cgroup
static __thread struct utlbuf_s ub = { NULL, 0 }; // util buffer for whole cgroup
static char lxc_none[] = "-";
static char lxc_oops[] = "?"; // used when memory alloc fails
/*
@@ -995,7 +995,7 @@ static char *lxc_containers (const char *path) {
if ((p1 = strstr(ub.buf, (delim = lxc_delm1)))
|| ((p1 = strstr(ub.buf, (delim = lxc_delm2)))
|| ((p1 = strstr(ub.buf, (delim = lxc_delm3)))))) {
static struct lxc_ele {
static __thread struct lxc_ele {
struct lxc_ele *next;
char *name;
} *anchor = NULL;
@@ -1112,8 +1112,8 @@ static void autogroup_fill (const char *path, proc_t *p) {
// The pid (tgid? tid?) is already in p, and a path to it in path, with some
// room to spare.
static proc_t *simple_readproc(PROCTAB *restrict const PT, proc_t *restrict const p) {
static struct utlbuf_s ub = { NULL, 0 }; // buf for stat,statm,status
static struct stat sb; // stat() buffer
static __thread struct utlbuf_s ub = { NULL, 0 }; // buf for stat,statm,status
static __thread struct stat sb; // stat() buffer
char *restrict const path = PT->path;
unsigned flags = PT->flags;
int rc = 0;
@@ -1235,8 +1235,8 @@ next_proc:
// t is the POSIX thread (task group member, generally not the leader)
// path is a path to the task, with some room to spare.
static proc_t *simple_readtask(PROCTAB *restrict const PT, proc_t *restrict const t, char *restrict const path) {
static struct utlbuf_s ub = { NULL, 0 }; // buf for stat,statm,status
static struct stat sb; // stat() buffer
static __thread struct utlbuf_s ub = { NULL, 0 }; // buf for stat,statm,status
static __thread struct stat sb; // stat() buffer
unsigned flags = PT->flags;
int rc = 0;
@@ -1356,7 +1356,7 @@ next_task:
// This finds processes in /proc in the traditional way.
// Return non-zero on success.
static int simple_nextpid(PROCTAB *restrict const PT, proc_t *restrict const p) {
static struct dirent *ent; /* dirent handle */
static __thread struct dirent *ent; /* dirent handle */
char *restrict const path = PT->path;
for (;;) {
ent = readdir(PT->procfs);
@@ -1374,7 +1374,7 @@ static int simple_nextpid(PROCTAB *restrict const PT, proc_t *restrict const p)
// This finds tasks in /proc/*/task/ in the traditional way.
// Return non-zero on success.
static int simple_nexttid(PROCTAB *restrict const PT, const proc_t *restrict const p, proc_t *restrict const t, char *restrict const path) {
static struct dirent *ent; /* dirent handle */
static __thread struct dirent *ent; /* dirent handle */
if(PT->taskdir_user != p->tgid){
if(PT->taskdir){
closedir(PT->taskdir);
@@ -1402,7 +1402,7 @@ static int simple_nexttid(PROCTAB *restrict const PT, const proc_t *restrict con
// This "finds" processes in a list that was given to openproc().
// Return non-zero on success. (tgid is a real headache)
static int listed_nextpid (PROCTAB *PT, proc_t *p) {
static struct utlbuf_s ub = { NULL, 0 };
static __thread struct utlbuf_s ub = { NULL, 0 };
pid_t pid = *(PT->pids)++;
char *path = PT->path;
@@ -1461,9 +1461,9 @@ out:
// the next unique process or task available. If no more are available,
// return a null pointer (boolean false).
proc_t *readeither (PROCTAB *restrict const PT, proc_t *restrict x) {
static proc_t skel_p; // skeleton proc_t, only uses tid + tgid
static proc_t *new_p; // for process/task transitions
static int canary, leader;
static __thread proc_t skel_p; // skeleton proc_t, only uses tid + tgid
static __thread proc_t *new_p; // for process/task transitions
static __thread int canary, leader;
char path[PROCPATHLEN];
proc_t *ret;
@@ -1511,7 +1511,7 @@ end_procs:
PROCTAB *openproc(unsigned flags, ...) {
va_list ap;
struct stat sbuf;
static int did_stat;
static __thread int did_stat;
PROCTAB *PT = calloc(1, sizeof(PROCTAB));
if (!PT)