diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
index 22d34a0be8b4c..5cb0eeec2c8a6 100644
--- a/tools/lib/api/fs/fs.c
+++ b/tools/lib/api/fs/fs.c
@@ -1,4 +1,5 @@
// SPDX-License-Identifier: GPL-2.0
+#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <limits.h>
@@ -10,6 +11,7 @@
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
+#include <pthread.h>
#include <unistd.h>
#include <sys/mount.h>
@@ -43,7 +45,7 @@
#define BPF_FS_MAGIC 0xcafe4a11
#endif
-static const char * const sysfs__fs_known_mountpoints[] = {
+static const char * const sysfs__known_mountpoints[] = {
"/sys",
0,
};
@@ -86,69 +88,70 @@ static const char * const bpf_fs__known_mountpoints[] = {
};
struct fs {
- const char *name;
- const char * const *mounts;
+ const char * const name;
+ const char * const * const mounts;
char *path;
- bool found;
- bool checked;
- long magic;
-};
-
-enum {
- FS__SYSFS = 0,
- FS__PROCFS = 1,
- FS__DEBUGFS = 2,
- FS__TRACEFS = 3,
- FS__HUGETLBFS = 4,
- FS__BPF_FS = 5,
+ pthread_mutex_t mount_mutex;
+ const long magic;
};
#ifndef TRACEFS_MAGIC
#define TRACEFS_MAGIC 0x74726163
#endif
-static struct fs fs__entries[] = {
- [FS__SYSFS] = {
- .name = "sysfs",
- .mounts = sysfs__fs_known_mountpoints,
- .magic = SYSFS_MAGIC,
- .checked = false,
- },
- [FS__PROCFS] = {
- .name = "proc",
- .mounts = procfs__known_mountpoints,
- .magic = PROC_SUPER_MAGIC,
- .checked = false,
- },
- [FS__DEBUGFS] = {
- .name = "debugfs",
- .mounts = debugfs__known_mountpoints,
- .magic = DEBUGFS_MAGIC,
- .checked = false,
- },
- [FS__TRACEFS] = {
- .name = "tracefs",
- .mounts = tracefs__known_mountpoints,
- .magic = TRACEFS_MAGIC,
- .checked = false,
- },
- [FS__HUGETLBFS] = {
- .name = "hugetlbfs",
- .mounts = hugetlbfs__known_mountpoints,
- .magic = HUGETLBFS_MAGIC,
- .checked = false,
- },
- [FS__BPF_FS] = {
- .name = "bpf",
- .mounts = bpf_fs__known_mountpoints,
- .magic = BPF_FS_MAGIC,
- .checked = false,
- },
-};
+static void fs__init_once(struct fs *fs);
+static const char *fs__mountpoint(const struct fs *fs);
+static const char *fs__mount(struct fs *fs);
+
+#define FS(lower_name, fs_name, upper_name) \
+static struct fs fs__##lower_name = { \
+ .name = #fs_name, \
+ .mounts = lower_name##__known_mountpoints, \
+ .magic = upper_name##_MAGIC, \
+ .mount_mutex = PTHREAD_MUTEX_INITIALIZER, \
+}; \
+ \
+static void lower_name##_init_once(void) \
+{ \
+ struct fs *fs = &fs__##lower_name; \
+ \
+ fs__init_once(fs); \
+} \
+ \
+const char *lower_name##__mountpoint(void) \
+{ \
+ static pthread_once_t init_once = PTHREAD_ONCE_INIT; \
+ struct fs *fs = &fs__##lower_name; \
+ \
+ pthread_once(&init_once, lower_name##_init_once); \
+ return fs__mountpoint(fs); \
+} \
+ \
+const char *lower_name##__mount(void) \
+{ \
+ const char *mountpoint = lower_name##__mountpoint(); \
+ struct fs *fs = &fs__##lower_name; \
+ \
+ if (mountpoint) \
+ return mountpoint; \
+ \
+ return fs__mount(fs); \
+} \
+ \
+bool lower_name##__configured(void) \
+{ \
+ return lower_name##__mountpoint() != NULL; \
+}
+
+FS(sysfs, sysfs, SYSFS);
+FS(procfs, procfs, PROC_SUPER);
+FS(debugfs, debugfs, DEBUGFS);
+FS(tracefs, tracefs, TRACEFS);
+FS(hugetlbfs, hugetlbfs, HUGETLBFS);
+FS(bpf_fs, bpf, BPF_FS);
static bool fs__read_mounts(struct fs *fs)
{
- bool found = false;
char type[100];
FILE *fp;
char path[PATH_MAX + 1];
@@ -157,22 +160,17 @@ static bool fs__read_mounts(struct fs *fs)
if (fp == NULL)
return false;
- while (!found &&
- fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
+ while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
path, type) == 2) {
if (strcmp(type, fs->name) == 0) {
- free(fs->path);
fs->path = strdup(path);
- if (!fs->path)
- return false;
- found = true;
+ fclose(fp);
+ return fs->path != NULL;
}
}
-
fclose(fp);
- fs->checked = true;
- return fs->found = found;
+ return false;
}
static int fs__valid_mount(const char *fs, long magic)
@@ -194,11 +192,9 @@ static bool fs__check_mounts(struct fs *fs)
ptr = fs->mounts;
while (*ptr) {
if (fs__valid_mount(*ptr, fs->magic) == 0) {
- free(fs->path);
fs->path = strdup(*ptr);
if (!fs->path)
return false;
- fs->found = true;
return true;
}
ptr++;
@@ -236,45 +232,26 @@ static bool fs__env_override(struct fs *fs)
if (!override_path)
return false;
- free(fs->path);
fs->path = strdup(override_path);
if (!fs->path)
return false;
- fs->found = true;
- fs->checked = true;
return true;
}
-static const char *fs__get_mountpoint(struct fs *fs)
+static void fs__init_once(struct fs *fs)
{
- if (fs__env_override(fs))
- return fs->path;
-
- if (fs__check_mounts(fs))
- return fs->path;
-
- if (fs__read_mounts(fs))
- return fs->path;
-
- return NULL;
+ if (!fs__env_override(fs) &&
+ !fs__check_mounts(fs) &&
+ !fs__read_mounts(fs)) {
+ assert(!fs->path);
+ } else {
+ assert(fs->path);
+ }
}
-static const char *fs__mountpoint(int idx)
+static const char *fs__mountpoint(const struct fs *fs)
{
- struct fs *fs = &fs__entries[idx];
-
- if (fs->found)
- return (const char *)fs->path;
-
- /* the mount point was already checked for the mount point
- * but and did not exist, so return NULL to avoid scanning again.
- * This makes the found and not found paths cost equivalent
- * in case of multiple calls.
- */
- if (fs->checked)
- return NULL;
-
- return fs__get_mountpoint(fs);
+ return fs->path;
}
static const char *mount_overload(struct fs *fs)
@@ -289,45 +266,29 @@ static const char *mount_overload(struct fs *fs)
return getenv(upper_name) ?: *fs->mounts;
}
-static const char *fs__mount(int idx)
+static const char *fs__mount(struct fs *fs)
{
- struct fs *fs = &fs__entries[idx];
const char *mountpoint;
- if (fs__mountpoint(idx))
- return (const char *)fs->path;
+ pthread_mutex_lock(&fs->mount_mutex);
- mountpoint = mount_overload(fs);
+ /* Check if path found inside the mutex to avoid races with other callers of mount. */
+ mountpoint = fs__mountpoint(fs);
+ if (mountpoint)
+ goto out;
- if (mount(NULL, mountpoint, fs->name, 0, NULL) < 0)
- return NULL;
-
- return fs__check_mounts(fs) ? fs->path : NULL;
-}
+ mountpoint = mount_overload(fs);
-#define FS(name, idx) \
-const char *name##__mountpoint(void) \
-{ \
- return fs__mountpoint(idx); \
-} \
- \
-const char *name##__mount(void) \
-{ \
- return fs__mount(idx); \
-} \
- \
-bool name##__configured(void) \
-{ \
- return name##__mountpoint() != NULL; \
+ if (mount(NULL, mountpoint, fs->name, 0, NULL) == 0 &&
+ fs__valid_mount(mountpoint, fs->magic) == 0) {
+ fs->path = strdup(mountpoint);
+ mountpoint = fs->path;
+ }
+out:
+ pthread_mutex_unlock(&fs->mount_mutex);
+ return mountpoint;
}
-FS(sysfs, FS__SYSFS);
-FS(procfs, FS__PROCFS);
-FS(debugfs, FS__DEBUGFS);
-FS(tracefs, FS__TRACEFS);
-FS(hugetlbfs, FS__HUGETLBFS);
-FS(bpf_fs, FS__BPF_FS);
-
int filename__read_int(const char *filename, int *value)
{
char line[64];