ReaderWriterLock.UpgradeToWriterLock Método
Definição
Faz o upgrade de um bloqueio de leitor para o bloqueio de gravador.Upgrades a reader lock to the writer lock.
Sobrecargas
| UpgradeToWriterLock(Int32) |
Atualiza um bloqueio de leitor para o bloqueio de gravador, usando um valor Int32 para o tempo limite.Upgrades a reader lock to the writer lock, using an Int32 value for the time-out. |
| UpgradeToWriterLock(TimeSpan) |
Faz o upgrade de um bloqueio de leitor para o bloqueio de gravador usando um valor |
UpgradeToWriterLock(Int32)
public:
System::Threading::LockCookie UpgradeToWriterLock(int millisecondsTimeout);
public System.Threading.LockCookie UpgradeToWriterLock (int millisecondsTimeout);
member this.UpgradeToWriterLock : int -> System.Threading.LockCookie
Public Function UpgradeToWriterLock (millisecondsTimeout As Integer) As LockCookie
Parâmetros
- millisecondsTimeout
- Int32
O tempo limite em milissegundos.The time-out in milliseconds.
Retornos
Um valor LockCookie.A LockCookie value.
Exceções
O millisecondsTimeout expira antes que a solicitação de bloqueio seja concedida.millisecondsTimeout expires before the lock request is granted.
Exemplos
O exemplo de código a seguir mostra como solicitar um bloqueio de leitor, atualizar o bloqueio de leitor para um bloqueio de gravador e fazer o downgrade para um bloqueio de leitor novamente.The following code example shows how to request a reader lock, upgrade the reader lock to a writer lock, and downgrade to a reader lock again.
Esse código é parte de um exemplo maior fornecido para a ReaderWriterLock classe.This code is part of a larger example provided for the ReaderWriterLock class.
// The complete code is located in the ReaderWriterLock
// class topic.
using namespace System;
using namespace System::Threading;
public ref class Test
{
public:
// Declaring the ReaderWriterLock at the class level
// makes it visible to all threads.
static ReaderWriterLock^ rwl = gcnew ReaderWriterLock;
// For this example, the shared resource protected by the
// ReaderWriterLock is just an integer.
static int resource = 0;
// The complete code is located in the ReaderWriterLock class topic.
using System;
using System.Threading;
public class Example
{
static ReaderWriterLock rwl = new ReaderWriterLock();
// Define the shared resource protected by the ReaderWriterLock.
static int resource = 0;
' The complete code is located in the ReaderWriterLock class topic.
Imports System.Threading
Public Module Example
Private rwl As New ReaderWriterLock()
' Define the shared resource protected by the ReaderWriterLock.
Private resource As Integer = 0
// Shows how to request a reader lock, upgrade the
// reader lock to the writer lock, and downgrade to a
// reader lock again.
static void UpgradeDowngrade( Random^ rnd, int timeOut )
{
try
{
rwl->AcquireReaderLock( timeOut );
try
{
// It is safe for this thread to read from
// the shared resource.
Display( String::Format( "reads resource value {0}", resource ) );
Interlocked::Increment( reads );
// If it is necessary to write to the resource,
// you must either release the reader lock and
// then request the writer lock, or upgrade the
// reader lock. Note that upgrading the reader lock
// puts the thread in the write queue, behind any
// other threads that might be waiting for the
// writer lock.
try
{
LockCookie lc = rwl->UpgradeToWriterLock( timeOut );
try
{
// It is safe for this thread to read or write
// from the shared resource.
resource = rnd->Next( 500 );
Display( String::Format( "writes resource value {0}", resource ) );
Interlocked::Increment( writes );
}
finally
{
// Ensure that the lock is released.
rwl->DowngradeFromWriterLock( lc );
}
}
catch ( ApplicationException^ )
{
// The upgrade request timed out.
Interlocked::Increment( writerTimeouts );
}
// When the lock has been downgraded, it is
// still safe to read from the resource.
Display( String::Format( "reads resource value {0}", resource ) );
Interlocked::Increment( reads );
}
finally
{
// Ensure that the lock is released.
rwl->ReleaseReaderLock();
}
}
catch ( ApplicationException^ )
{
// The reader lock request timed out.
Interlocked::Increment( readerTimeouts );
}
}
// Requests a reader lock, upgrades the reader lock to the writer
// lock, and downgrades it to a reader lock again.
static void UpgradeDowngrade(Random rnd, int timeOut)
{
try {
rwl.AcquireReaderLock(timeOut);
try {
// It's safe for this thread to read from the shared resource.
Display("reads resource value " + resource);
Interlocked.Increment(ref reads);
// To write to the resource, either release the reader lock and
// request the writer lock, or upgrade the reader lock. Upgrading
// the reader lock puts the thread in the write queue, behind any
// other threads that might be waiting for the writer lock.
try {
LockCookie lc = rwl.UpgradeToWriterLock(timeOut);
try {
// It's safe for this thread to read or write from the shared resource.
resource = rnd.Next(500);
Display("writes resource value " + resource);
Interlocked.Increment(ref writes);
}
finally {
// Ensure that the lock is released.
rwl.DowngradeFromWriterLock(ref lc);
}
}
catch (ApplicationException) {
// The upgrade request timed out.
Interlocked.Increment(ref writerTimeouts);
}
// If the lock was downgraded, it's still safe to read from the resource.
Display("reads resource value " + resource);
Interlocked.Increment(ref reads);
}
finally {
// Ensure that the lock is released.
rwl.ReleaseReaderLock();
}
}
catch (ApplicationException) {
// The reader lock request timed out.
Interlocked.Increment(ref readerTimeouts);
}
}
' Requests a reader lock, upgrades the reader lock to the writer
' lock, and downgrades it to a reader lock again.
Sub UpgradeDowngrade(rnd As Random, timeOut As Integer)
Try
rwl.AcquireReaderLock(timeOut)
Try
' It's safe for this thread to read from the shared resource.
Display("reads resource value " & resource)
Interlocked.Increment(reads)
' To write to the resource, either release the reader lock and
' request the writer lock, or upgrade the reader lock. Upgrading
' the reader lock puts the thread in the write queue, behind any
' other threads that might be waiting for the writer lock.
Try
Dim lc As LockCookie = rwl.UpgradeToWriterLock(timeOut)
Try
' It's safe for this thread to read or write from the shared resource.
resource = rnd.Next(500)
Display("writes resource value " & resource)
Interlocked.Increment(writes)
Finally
' Ensure that the lock is released.
rwl.DowngradeFromWriterLock(lc)
End Try
Catch ex As ApplicationException
' The upgrade request timed out.
Interlocked.Increment(writerTimeouts)
End Try
' If the lock was downgraded, it's still safe to read from the resource.
Display("reads resource value " & resource)
Interlocked.Increment(reads)
Finally
' Ensure that the lock is released.
rwl.ReleaseReaderLock()
End Try
Catch ex As ApplicationException
' The reader lock request timed out.
Interlocked.Increment(readerTimeouts)
End Try
End Sub
};
}
End Module
Comentários
Quando um thread chama UpgradeToWriterLock o bloqueio de leitor é liberado, independentemente da contagem de bloqueios, e o thread vai até o final da fila para o bloqueio do gravador.When a thread calls UpgradeToWriterLock the reader lock is released, regardless of the lock count, and the thread goes to the end of the queue for the writer lock. Assim, outros threads podem gravar no recurso antes que o thread que solicitou a atualização receba o bloqueio do gravador.Thus, other threads might write to the resource before the thread that requested the upgrade is granted the writer lock.
Importante
A exceção de tempo limite não é lançada até que o thread que chamou o UpgradeToWriterLock método possa readquirir o bloqueio do leitor.The time-out exception is not thrown until the thread that called the UpgradeToWriterLock method can reacquire the reader lock. Se não houver nenhum outro thread Aguardando o bloqueio do gravador, isso ocorrerá imediatamente.If there are no other threads waiting for the writer lock, this happens immediately. No entanto, se outro thread for enfileirado para o bloqueio do gravador, o thread que chamou o UpgradeToWriterLock método não poderá readquirir o bloqueio do leitor até que todos os leitores atuais tenham liberado seus bloqueios e um thread tenha adquirido e liberado o bloqueio do gravador.However, if another thread is queued for the writer lock, the thread that called the UpgradeToWriterLock method cannot reacquire the reader lock until all current readers have released their locks, and one thread has acquired and released the writer lock. Isso é verdadeiro mesmo que o outro thread que solicitou o bloqueio do gravador o solicitou após o thread atual chamar o UpgradeToWriterLock método.This is true even if the other thread that requested the writer lock requested it after the current thread called the UpgradeToWriterLock method.
Para restaurar o estado do bloqueio, chame DowngradeFromWriterLock usando o LockCookie retornado por UpgradeToWriterLock .To restore the lock state, call DowngradeFromWriterLock using the LockCookie returned by UpgradeToWriterLock. Não use isso LockCookie com RestoreLock .Do not use this LockCookie with RestoreLock.
Quando um thread não tem nenhum bloqueio de leitor, não use UpgradeToWriterLock .When a thread has no reader lock, do not use UpgradeToWriterLock. Use AcquireWriterLock em seu lugar.Use AcquireWriterLock instead.
Para obter valores de tempo limite válidos, consulte ReaderWriterLock .For valid time-out values, see ReaderWriterLock.
Aplica-se a
UpgradeToWriterLock(TimeSpan)
Faz o upgrade de um bloqueio de leitor para o bloqueio de gravador usando um valor TimeSpan para o tempo limite.Upgrades a reader lock to the writer lock, using a TimeSpan value for the time-out.
public:
System::Threading::LockCookie UpgradeToWriterLock(TimeSpan timeout);
public System.Threading.LockCookie UpgradeToWriterLock (TimeSpan timeout);
member this.UpgradeToWriterLock : TimeSpan -> System.Threading.LockCookie
Public Function UpgradeToWriterLock (timeout As TimeSpan) As LockCookie
Parâmetros
- timeout
- TimeSpan
O TimeSpan que especifica o período de tempo limite.The TimeSpan specifying the time-out period.
Retornos
Um valor LockCookie.A LockCookie value.
Exceções
O timeout expira antes que a solicitação de bloqueio seja concedida.timeout expires before the lock request is granted.
timeout especifica um valor negativo diferente de -1 milissegundo.timeout specifies a negative value other than -1 milliseconds.
Comentários
Quando um thread chama UpgradeToWriterLock o bloqueio de leitor é liberado, independentemente da contagem de bloqueios, e o thread vai até o final da fila para o bloqueio do gravador.When a thread calls UpgradeToWriterLock the reader lock is released, regardless of the lock count, and the thread goes to the end of the queue for the writer lock. Assim, outros threads podem gravar no recurso antes que o thread que solicitou a atualização receba o bloqueio do gravador.Thus, other threads might write to the resource before the thread that requested the upgrade is granted the writer lock.
Importante
A exceção de tempo limite não é lançada até que o thread que chamou o UpgradeToWriterLock método possa readquirir o bloqueio do leitor.The time-out exception is not thrown until the thread that called the UpgradeToWriterLock method can reacquire the reader lock. Se não houver nenhum outro thread Aguardando o bloqueio do gravador, isso ocorrerá imediatamente.If there are no other threads waiting for the writer lock, this happens immediately. No entanto, se outro thread for enfileirado para o bloqueio do gravador, o thread que chamou o UpgradeToWriterLock método não poderá readquirir o bloqueio do leitor até que todos os leitores atuais tenham liberado seus bloqueios e um thread tenha adquirido e liberado o bloqueio do gravador.However, if another thread is queued for the writer lock, the thread that called the UpgradeToWriterLock method cannot reacquire the reader lock until all current readers have released their locks, and one thread has acquired and released the writer lock. Isso é verdadeiro mesmo que o outro thread que solicitou o bloqueio do gravador o solicitou após o thread atual chamar o UpgradeToWriterLock método.This is true even if the other thread that requested the writer lock requested it after the current thread called the UpgradeToWriterLock method.
Para restaurar o estado do bloqueio, chame DowngradeFromWriterLock usando o LockCookie retornado por UpgradeToWriterLock .To restore the lock state, call DowngradeFromWriterLock using the LockCookie returned by UpgradeToWriterLock. Não use isso LockCookie com RestoreLock .Do not use this LockCookie with RestoreLock.
Quando um thread não tem nenhum bloqueio de leitor, não use UpgradeToWriterLock .When a thread has no reader lock, do not use UpgradeToWriterLock. Use AcquireWriterLock em seu lugar.Use AcquireWriterLock instead.
Para obter valores de tempo limite válidos, consulte ReaderWriterLock .For valid time-out values, see ReaderWriterLock.