1// Copyright (c) 2009 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5#include <errno.h> 6#include <fcntl.h> 7#include <sys/file.h> 8 9#include "chrome/browser/process_singleton.h" 10 11#include "base/eintr_wrapper.h" 12#include "base/file_util.h" 13#include "base/metrics/histogram.h" 14#include "chrome/common/chrome_constants.h" 15 16namespace { 17 18// From "man 2 intro", the largest errno is |EOPNOTSUPP|, which is 19// |102|. Since the histogram memory usage is proportional to this 20// number, using the |102| directly rather than the macro. 21const int kMaxErrno = 102; 22 23} // namespace 24 25// This class is used to funnel messages to a single instance of the browser 26// process. This is needed for several reasons on other platforms. 27// 28// On Windows, when the user re-opens the application from the shell (e.g. an 29// explicit double-click, a shortcut that opens a webpage, etc.) we need to send 30// the message to the currently-existing copy of the browser. 31// 32// On Linux, opening a URL is done by creating an instance of the web browser 33// process and passing it the URL to go to on its commandline. 34// 35// Neither of those cases apply on the Mac. Launch Services ensures that there 36// is only one instance of the process, and we get URLs to open via AppleEvents 37// and, once again, the Launch Services system. We have no need to manage this 38// ourselves. An exclusive lock is used to flush out anyone making incorrect 39// assumptions. 40 41ProcessSingleton::ProcessSingleton(const FilePath& user_data_dir) 42 : locked_(false), 43 foreground_window_(NULL), 44 lock_path_(user_data_dir.Append(chrome::kSingletonLockFilename)), 45 lock_fd_(-1) { 46} 47 48ProcessSingleton::~ProcessSingleton() { 49 // Make sure the lock is released. Process death will also release 50 // it, even if this is not called. 51 Cleanup(); 52} 53 54ProcessSingleton::NotifyResult ProcessSingleton::NotifyOtherProcess() { 55 // This space intentionally left blank. 56 return PROCESS_NONE; 57} 58 59ProcessSingleton::NotifyResult ProcessSingleton::NotifyOtherProcessOrCreate() { 60 // Windows tries NotifyOtherProcess() first. 61 return Create() ? PROCESS_NONE : PROFILE_IN_USE; 62} 63 64// Attempt to acquire an exclusive lock on an empty file in the 65// profile directory. Returns |true| if it gets the lock. Returns 66// |false| if the lock is held, or if there is an error. 67// TODO(shess): Rather than logging failures, popup an alert. Punting 68// that for now because it would require confidence that this code is 69// never called in a situation where an alert wouldn't work. 70// http://crbug.com/59061 71bool ProcessSingleton::Create() { 72 DCHECK_EQ(-1, lock_fd_) << "lock_path_ is already open."; 73 74 lock_fd_ = HANDLE_EINTR(open(lock_path_.value().c_str(), 75 O_RDONLY | O_CREAT, 0644)); 76 if (lock_fd_ == -1) { 77 const int capture_errno = errno; 78 DPCHECK(lock_fd_ != -1) << "Unexpected failure opening profile lockfile"; 79 UMA_HISTOGRAM_ENUMERATION("ProcessSingleton.OpenError", 80 capture_errno, kMaxErrno); 81 return false; 82 } 83 84 // Acquire an exclusive lock in non-blocking fashion. If the lock 85 // is already held, this will return |EWOULDBLOCK|. 86 int rc = HANDLE_EINTR(flock(lock_fd_, LOCK_EX|LOCK_NB)); 87 if (rc == -1) { 88 const int capture_errno = errno; 89 DPCHECK(errno == EWOULDBLOCK) 90 << "Unexpected failure locking profile lockfile"; 91 92 Cleanup(); 93 94 // Other errors indicate something crazy is happening. 95 if (capture_errno != EWOULDBLOCK) { 96 UMA_HISTOGRAM_ENUMERATION("ProcessSingleton.LockError", 97 capture_errno, kMaxErrno); 98 return false; 99 } 100 101 // The file is open by another process and locked. 102 LOG(ERROR) << "Unable to obtain profile lock."; 103 return false; 104 } 105 106 return true; 107} 108 109void ProcessSingleton::Cleanup() { 110 // Closing the file also releases the lock. 111 if (lock_fd_ != -1) { 112 int rc = HANDLE_EINTR(close(lock_fd_)); 113 DPCHECK(!rc) << "Closing lock_fd_:"; 114 } 115 lock_fd_ = -1; 116} 117