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udev: Fix O(n^2) device walking issue (closes #9092)

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I believe there was a O(n^2) device walking issues on startup

- MaybeAddDevice gets called for every device at startup
- MaybeAddDevice calls IsJoystick
- IsJoystick calls SDL_UDEV_GetProductInfo
- SDL_UDEV_GetProductInfo calls udev_enumerate_scan_devices
- udev_enumerate_scan_devices walks all the devices

Prior to commit 3b1e0e1 this was mostly masked as IsJoystick only
called SDL_UDEV_GetProductInfo when a JSIOCGNAME ioctl was
successful. This fixes the O(n^2) behaviour by directly getting
the device via udev_device_new_from_devnum (based on type, major,
and minor number) instead of enumerating everything via
udev_enumerate_scan_devices and matching on name.
This commit is contained in:
Tyson Whitehead
2024-03-23 14:10:28 -04:00
committed by Sam Lantinga
parent 6ba3e56538
commit 6e1611cc77
1 changed files with 44 additions and 45 deletions
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89
src/core/linux/SDL_udev.c
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@@ -31,6 +31,7 @@
#ifdef SDL_USE_LIBUDEV
#include <linux/input.h>
#include <sys/stat.h>
#include "SDL_assert.h"
#include "SDL_evdev_capabilities.h"
@@ -227,61 +228,59 @@ void SDL_UDEV_Scan(void)
SDL_bool SDL_UDEV_GetProductInfo(const char *device_path, Uint16 *vendor, Uint16 *product, Uint16 *version, int *class)
{
struct udev_enumerate *enumerate = NULL;
struct udev_list_entry *devs = NULL;
struct udev_list_entry *item = NULL;
SDL_bool found = SDL_FALSE;
struct stat statbuf;
char type;
struct udev_device *dev;
const char* val;
int class_temp;
if (!_this) {
return SDL_FALSE;
}
enumerate = _this->syms.udev_enumerate_new(_this->udev);
if (!enumerate) {
SDL_SetError("udev_enumerate_new() failed");
if (stat(device_path, &statbuf) == -1) {
return SDL_FALSE;
}
_this->syms.udev_enumerate_scan_devices(enumerate);
devs = _this->syms.udev_enumerate_get_list_entry(enumerate);
for (item = devs; item && !found; item = _this->syms.udev_list_entry_get_next(item)) {
const char *path = _this->syms.udev_list_entry_get_name(item);
struct udev_device *dev = _this->syms.udev_device_new_from_syspath(_this->udev, path);
if (dev) {
const char *val = NULL;
const char *existing_path;
existing_path = _this->syms.udev_device_get_devnode(dev);
if (existing_path && SDL_strcmp(device_path, existing_path) == 0) {
int class_temp;
found = SDL_TRUE;
val = _this->syms.udev_device_get_property_value(dev, "ID_VENDOR_ID");
if (val) {
*vendor = (Uint16)SDL_strtol(val, NULL, 16);
}
val = _this->syms.udev_device_get_property_value(dev, "ID_MODEL_ID");
if (val) {
*product = (Uint16)SDL_strtol(val, NULL, 16);
}
val = _this->syms.udev_device_get_property_value(dev, "ID_REVISION");
if (val) {
*version = (Uint16)SDL_strtol(val, NULL, 16);
}
class_temp = device_class(dev);
if (class_temp) {
*class = class_temp;
}
}
_this->syms.udev_device_unref(dev);
}
if (S_ISBLK(statbuf.st_mode)) {
type = 'b';
}
else if (S_ISCHR(statbuf.st_mode)) {
type = 'c';
}
else {
return SDL_FALSE;
}
_this->syms.udev_enumerate_unref(enumerate);
return found;
dev = _this->syms.udev_device_new_from_devnum(_this->udev, type, statbuf.st_rdev);
if (!dev) {
return SDL_FALSE;
}
val = _this->syms.udev_device_get_property_value(dev, "ID_VENDOR_ID");
if (val) {
*vendor = (Uint16)SDL_strtol(val, NULL, 16);
}
val = _this->syms.udev_device_get_property_value(dev, "ID_MODEL_ID");
if (val) {
*product = (Uint16)SDL_strtol(val, NULL, 16);
}
val = _this->syms.udev_device_get_property_value(dev, "ID_REVISION");
if (val) {
*version = (Uint16)SDL_strtol(val, NULL, 16);
}
class_temp = device_class(dev);
if (class_temp) {
*class = class_temp;
}
_this->syms.udev_device_unref(dev);
return SDL_TRUE;
}
void SDL_UDEV_UnloadLibrary(void)