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d010b02e86
Summary: In follow-up to https://github.com/facebook/rocksdb/issues/11922, fix a race in functions like CreateColumnFamily and SetDBOptions where the DB reports one option setting but a different one is left in effect. To fix, we can add an extra mutex around these rare operations. We don't want to hold the DB mutex during I/O or other slow things because of the many purposes it serves, but a mutex more limited to these cases should be fine. I believe this would fix a write-write race in https://github.com/facebook/rocksdb/issues/10079 but not the read-write race. Intended follow-up to this: * Should be able to remove write thread synchronization from DBImpl::WriteOptionsFile Pull Request resolved: https://github.com/facebook/rocksdb/pull/11929 Test Plan: Added two mini-stress style regression tests that fail with >1% probability before this change: DBOptionsTest::SetStatsDumpPeriodSecRace ColumnFamilyTest::CreateAndDropPeriodicRace I haven't reproduced such an inconsistency between in-memory options and on disk latest options, but this change at least improves safety and adds a test anyway: DBOptionsTest::SetStatsDumpPeriodSecRace Reviewed By: ajkr Differential Revision: D50024506 Pulled By: pdillinger fbshipit-source-id: 1e99a9ed4d96fdcf3ac5061ec6b3cee78aecdda4
102 lines
3.5 KiB
C++
102 lines
3.5 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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//
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// This file contains the specification, but not the implementations,
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// of the types/operations/etc. that should be defined by a platform
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// specific port_<platform>.h file. Use this file as a reference for
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// how to port this package to a new platform.
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#pragma once
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namespace ROCKSDB_NAMESPACE {
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namespace port {
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// TODO(jorlow): Many of these belong more in the environment class rather than
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// here. We should try moving them and see if it affects perf.
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// The following boolean constant must be true on a little-endian machine
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// and false otherwise.
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static const bool kLittleEndian = true /* or some other expression */;
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// ------------------ Threading -------------------
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// A Mutex represents an exclusive lock.
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class Mutex {
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public:
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Mutex();
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~Mutex();
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// Lock the mutex. Waits until other lockers have exited.
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// Will deadlock if the mutex is already locked by this thread.
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void Lock();
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// Unlock the mutex.
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// REQUIRES: This mutex was locked by this thread.
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void Unlock();
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// Optionally crash if this thread does not hold this mutex.
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// The implementation must be fast, especially if NDEBUG is
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// defined. The implementation is allowed to skip all checks.
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void AssertHeld() const;
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};
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class CondVar {
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public:
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explicit CondVar(Mutex* mu);
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~CondVar();
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// Atomically release *mu and block on this condition variable until
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// either a call to SignalAll(), or a call to Signal() that picks
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// this thread to wakeup.
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// REQUIRES: this thread holds *mu
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void Wait();
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// If there are some threads waiting, wake up at least one of them.
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void Signal();
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// Wake up all waiting threads.
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void SignallAll();
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};
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// Thread-safe initialization.
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// Used as follows:
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// static port::OnceType init_control = LEVELDB_ONCE_INIT;
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// static void Initializer() { ... do something ...; }
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// ...
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// port::InitOnce(&init_control, &Initializer);
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using OnceType = intptr_t;
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#define LEVELDB_ONCE_INIT 0
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extern void InitOnce(port::OnceType*, void (*initializer)());
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// ------------------ Compression -------------------
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// Store the snappy compression of "input[0,input_length-1]" in *output.
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// Returns false if snappy is not supported by this port.
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extern bool Snappy_Compress(const char* input, size_t input_length,
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std::string* output);
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// If input[0,input_length-1] looks like a valid snappy compressed
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// buffer, store the size of the uncompressed data in *result and
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// return true. Else return false.
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extern bool Snappy_GetUncompressedLength(const char* input, size_t length,
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size_t* result);
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// Attempt to snappy uncompress input[0,input_length-1] into *output.
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// Returns true if successful, false if the input is invalid lightweight
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// compressed data.
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//
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// REQUIRES: at least the first "n" bytes of output[] must be writable
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// where "n" is the result of a successful call to
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// Snappy_GetUncompressedLength.
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extern bool Snappy_Uncompress(const char* input_data, size_t input_length,
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char* output);
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} // namespace port
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} // namespace ROCKSDB_NAMESPACE
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