2c28919d48
In some scenarios (e.g. apexd or userspace reboot), dm-devices are getting deleted and re-created. Since this operation can be racy (newly created device can get the same path as the previously deleted one, resulting in the unexpected ENOENT errors on a system call to the path), it will be nice to have an API that blocks until ueventd processes corresponding udev events. Test: libdm_test Bug: 143970043 Bug: 122059364 Change-Id: I31a19afd9e245bf5e3554011bdde1c3cc4878f1c
66 lines
2.2 KiB
C++
66 lines
2.2 KiB
C++
// Copyright (C) 2019 The Android Open Source Project
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "utility.h"
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#include <errno.h>
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#include <unistd.h>
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#include <thread>
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using namespace std::literals;
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namespace android {
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namespace dm {
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bool WaitForCondition(const std::function<WaitResult()>& condition,
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const std::chrono::milliseconds& timeout_ms) {
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auto start_time = std::chrono::steady_clock::now();
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while (true) {
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auto result = condition();
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if (result == WaitResult::Done) return true;
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if (result == WaitResult::Fail) return false;
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std::this_thread::sleep_for(20ms);
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auto now = std::chrono::steady_clock::now();
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auto time_elapsed = std::chrono::duration_cast<std::chrono::milliseconds>(now - start_time);
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if (time_elapsed > timeout_ms) return false;
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}
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}
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bool WaitForFile(const std::string& path, const std::chrono::milliseconds& timeout_ms) {
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auto condition = [&]() -> WaitResult {
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// If the file exists but returns EPERM or something, we consider the
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// condition met.
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if (access(path.c_str(), F_OK) != 0) {
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if (errno == ENOENT) return WaitResult::Wait;
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}
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return WaitResult::Done;
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};
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return WaitForCondition(condition, timeout_ms);
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}
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bool WaitForFileDeleted(const std::string& path, const std::chrono::milliseconds& timeout_ms) {
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auto condition = [&]() -> WaitResult {
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if (access(path.c_str(), F_OK) == 0 || errno != ENOENT) {
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return WaitResult::Wait;
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}
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return WaitResult::Done;
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};
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return WaitForCondition(condition, timeout_ms);
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}
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} // namespace dm
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} // namespace android
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