fc2e3a7421
This patch implements the new update mutex using nsProfileLock for all platforms. The logic is implemented in the new nsIUpdateMutex XPCOM component. Compability with the legacy update mutex is not preserved. Depends on D222156 Differential Revision: https://phabricator.services.mozilla.com/D222157
77 lines
2.6 KiB
C++
77 lines
2.6 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim:set ts=2 sw=2 sts=2 et cindent: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef nsUpdateMutex_h__
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#define nsUpdateMutex_h__
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#include "nsIUpdateService.h"
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#include "nsProfileLock.h"
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#include "mozilla/StaticMutex.h"
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/**
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* A primitive object type suitable for acquiring the update mutex. It is
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* composed of two parts:
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* - a nsProfileLock taken on the update directory, to ensure that if two
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* instances running from the same application path try to acquire the
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* update mutex simultaneously, only one of them succeeds;
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* - a StaticMutex, to ensure that even within the same instance of the
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* application, it is never possible to successfully acquire two
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* UpdateMutexImpl objects simultaneously.
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*
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* While the second part is not strictly required, it makes reasoning about
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* these objects easier, and it helps us simulate an acquisition coming from
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* another instance in tests.
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*
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* Contrary to a nsIUpdateMutex object, an UpdateMutexImpl object does not
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* keep track of whether it is currently locked or unlocked. Therefore, it is
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* the responsibility of the caller to guarantee the following:
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* - a call to Unlock() must only occur after a matching successful call to
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* TryLock();
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* - no second call to TryLock() should ever occur after a successful first
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* call to TryLock(), unless a call to Unlock() occured in the middle.
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*/
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class MOZ_CAPABILITY("mutex") UpdateMutexImpl {
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public:
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[[nodiscard]] bool TryLock() MOZ_TRY_ACQUIRE(true);
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void Unlock() MOZ_CAPABILITY_RELEASE();
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private:
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static mozilla::StaticMutex sInProcessMutex;
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nsProfileLock mCrossProcessLock;
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};
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/**
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* An XPCOM wrapper for the UpdateMutexImpl primitive type, achieving the same
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* goals but through a safe XPCOM-compatible nsIUpdateMutex interface.
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*
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* Contrary to UpdateMutexImpl objects, nsUpdateMutex objects track whether
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* they are currently locked or unlocked. It is therefore always safe to call
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* TryLock() or Unlock() on a nsUpdateMutex object.
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*
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* See nsIUpdateMutex in nsUpdateService.idl for more details.
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*/
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class nsUpdateMutex final : public nsIUpdateMutex {
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public:
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explicit nsUpdateMutex() = default;
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NS_DECL_THREADSAFE_ISUPPORTS
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NS_DECL_NSIUPDATEMUTEX
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private:
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UpdateMutexImpl mUpdateMutexImpl;
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bool mIsLocked{};
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virtual ~nsUpdateMutex() {
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if (mIsLocked) {
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Unlock();
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}
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}
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};
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#endif // nsUpdateMutex_h__
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