ueventd: remove PlatformDeviceList
In order to create symlinks for USB and block devices, the path for
their parent platform device must be known.
Previously, ueventd would save each platform device that it encounters
to a list and query this list when creating the symlinks. That,
however, is racy because the uevent socket does not differentiate
uevents from RegenerateUevents() and uevents sent by the kernel when
probing a device first the first time. The below scenario is the
faulty case:
1) Kernel probes parent platform device for a block device
2) ueventd calls RegenerateUevents() and starts processing uevents
3) Kernel probes block device and sends its uevents
4) ueventd picks up the block device uevent during its uevent processing,
without yet regenerating the platform device uevent, causing improper
symlinks to be created.
This change stops storing the platform devices in a list, and instead
traverses up the directory structure for each USB or block device
until it reaches a platform device, defined as one whose subsystem is
the platform bus. This fixes the race and simplifies the ueventd
code.
Bug: 62436493
Bug: 62681642
Test: Boot bullhead
Test: Boot sailfish
Test: Init unit tests
Test: Boot hikey + hotplug/unplug sdcard
Change-Id: I21636355d8e434f30e0cba568598a6cf139e67f9
diff --git a/init/devices_test.cpp b/init/devices_test.cpp
index 41b101b..e1e4e49 100644
--- a/init/devices_test.cpp
+++ b/init/devices_test.cpp
@@ -16,33 +16,29 @@
#include "devices.h"
-#include <string>
-#include <vector>
-
#include <android-base/scopeguard.h>
+#include <android-base/test_utils.h>
#include <gtest/gtest.h>
+#include "util.h"
+
+using namespace std::string_literals;
+
class DeviceHandlerTester {
public:
- void AddPlatformDevice(const std::string& path) {
- Uevent uevent = {
- .action = "add", .subsystem = "platform", .path = path,
- };
- device_handler_.HandlePlatformDeviceEvent(uevent);
- }
-
- void RemovePlatformDevice(const std::string& path) {
- Uevent uevent = {
- .action = "remove", .subsystem = "platform", .path = path,
- };
- device_handler_.HandlePlatformDeviceEvent(uevent);
- }
-
- void TestGetSymlinks(const std::string& platform_device_name, const Uevent& uevent,
+ void TestGetSymlinks(const std::string& platform_device, const Uevent& uevent,
const std::vector<std::string> expected_links, bool block) {
- AddPlatformDevice(platform_device_name);
- auto platform_device_remover = android::base::make_scope_guard(
- [this, &platform_device_name]() { RemovePlatformDevice(platform_device_name); });
+ TemporaryDir fake_sys_root;
+ device_handler_.sysfs_mount_point_ = fake_sys_root.path;
+
+ std::string platform_device_dir = fake_sys_root.path + platform_device;
+ mkdir_recursive(platform_device_dir, 0777, nullptr);
+
+ std::string platform_bus = fake_sys_root.path + "/bus/platform"s;
+ mkdir_recursive(platform_bus, 0777, nullptr);
+ symlink(platform_bus.c_str(), (platform_device_dir + "/subsystem").c_str());
+
+ mkdir_recursive(android::base::Dirname(fake_sys_root.path + uevent.path), 0777, nullptr);
std::vector<std::string> result;
if (block) {
@@ -65,30 +61,6 @@
DeviceHandler device_handler_;
};
-TEST(device_handler, PlatformDeviceList) {
- PlatformDeviceList platform_device_list;
-
- platform_device_list.Add("/devices/platform/some_device_name");
- platform_device_list.Add("/devices/platform/some_device_name/longer");
- platform_device_list.Add("/devices/platform/other_device_name");
- EXPECT_EQ(3U, platform_device_list.size());
-
- std::string out_path;
- EXPECT_FALSE(platform_device_list.Find("/devices/platform/not_found", &out_path));
- EXPECT_EQ("", out_path);
-
- EXPECT_FALSE(platform_device_list.Find("/devices/platform/some_device_name_with_same_prefix",
- &out_path));
-
- EXPECT_TRUE(platform_device_list.Find("/devices/platform/some_device_name/longer/longer_child",
- &out_path));
- EXPECT_EQ("/devices/platform/some_device_name/longer", out_path);
-
- EXPECT_TRUE(
- platform_device_list.Find("/devices/platform/some_device_name/other_child", &out_path));
- EXPECT_EQ("/devices/platform/some_device_name", out_path);
-}
-
TEST(device_handler, get_character_device_symlinks_success) {
const char* platform_device = "/devices/platform/some_device_name";
Uevent uevent = {