MECHANISM FOR IRREVOCABLE TRANSACTIONS

• US 20110320776A1
• Filed: 09/13/2011
• Published: 12/29/2011
• Est. Priority Date: 12/28/2006
• Status: Active Grant

• Current Assignee: Adam Welc, Ali-Reza Adl-Tabatabai, Bratin Saha
• Original Assignee: Adam Welc, Ali-Reza Adl-Tabatabai, Bratin Saha
• Inventors: Welc, Adam, Saha, Bratin, Adl-Tabatabai, Ali-Reza
• Granted Patent: US 8,627,048 B2
• Time in Patent Office: Days
• US Class Current: 712/218
• CPC Class Codes: G06F 9/3004 to perform operations on memory
• CPC Class Codes: G06F 9/30087 Synchronisation or serialisation instructions
• CPC Class Codes: G06F 9/3858 Result writeback, i.e. updating the architectural state or memory
• CPC Class Codes: G06F 9/3863 using multiple copies of the architectural state, e.g. shadow registers
• CPC Class Codes: G06F 9/526 Mutual exclusion algorithms

Abstract

A method and apparatus for designating and handling irrevocable transactions is herein described. In response to detecting an irrevocable event, such as an I/O operation, a user-defined irrevocable designation, and a dynamic failure profile, a transaction is designated as irrevocable. In response to designating a transaction as irrevocable, Single Owner Read Locks (SORLs) are acquired for previous and subsequent reads in the irrevocably designated transaction to ensure the transaction is able to complete without modification to locations read from, while permitting remote resources to load from those locations to continue execution.

Claims

1. A machine readable medium including program code which, when executed by a machine, causes the machine to perform the operations of:

in response to encountering an irrevocable event associated with a transaction to be executed on a processor within the machine,

designating the transaction as irrevocable in a transaction descriptor software data structure; and

acquiring a read lock for a data object associated with a transactional read of the transaction when the transaction is designated as irrevocable, wherein the read lock, when acquired, is to allow a remote transaction to read the data object and only the transaction designated as irrevocable to write to the data object.

2. The machine readable medium of claim 1, wherein the transaction descriptor software data structure is to be held in a system memory coupled to the processor, and wherein the transaction descriptor software data structure is to include an irrevocable transaction field, when set, to designate the transaction as irrevocable.

3. The machine readable medium of claim 2, wherein the system memory is also to hold:

the data object; and

wherein a meta-data location to be associated with the data object is to hold;

an unlocked value to represent the data object is unlocked in response to no transaction owning a lock on the data object,

a read and write locked value, which comprises a reference to the transaction descriptor software data structure, to represent the data object is read and write locked by the transaction in response to a transactional write to the data object from the transaction, and

a read lock value to represent the read lock for the data object is acquired in response to the transactional read reading from the data object, when the irrevocable transaction field is set to designate the first transaction as irrevocable.

4. The machine readable medium of claim 3, wherein the irrevocable event is selected from a group consisting of an I/O operation of the first number of operations, a system call operation of the first number of operations, a user-defined irrevocable transaction identifier operation of the first number of operations, and a dynamic failure profile of the first transaction to request the first transaction is to be designated as an irrevocable transaction.

5. The machine readable medium of claim 3, wherein, when the irrevocable transaction field is set to designate the transaction is irrevocable, a transactional read of the data object from the transaction is to be performed, and a remote transaction has already updated the meta-data location to a read and write lock value, which comprises a reference to a remote transaction descriptor software data structure associated with the remote transaction, the program code is further to cause the machine to perform conflict resolution between a first resource associated with the transaction and a remote resource associated with the remote transaction.

6. The machine readable medium of claim 5, wherein the machine to perform conflict resolution comprises:

the machine to execute conflict resolution code to implement a conflict resolution policy, the confliction resolution policy to be selected from a group consisting of waiting for the remote resource to update the meta-data location to the unlocked value to represent the data object is unlocked, aborting the execution of the remote transaction on the remote resource and allowing the first resource to set the meta-data location to the read lock value to represent the data object is read locked by the transaction in response to the transactional read of the data object from the transaction, and waiting for an amount of time for the remote resource to update the meta-data location to the unlocked value to represent the data object is unlocked and, responsive to the remote resource not setting the meta-data location to the unlocked value in the amount of time, aborting execution of the remote transaction on the remote resource and allowing the first resource to set the meta-data location to the read lock value to represent the data object is read locked by the transaction in response to the transactional read of the data object from the transaction.

7. A non-transitory machine readable medium including program code which, when executed by a machine, causes the machine to perform the operations of:

associating a meta-data location with an address for a data object through a software algorithm;

responsive to the meta-data location holding an unlocked value;

updating the meta-data location to a read and write locked value associated with a transaction before a transactional write from the transaction;

updating the meta-data location to a read locked value to allow other transactions to read the data-object and only the transaction to write to the data object before a transactional read from the transaction in response to the transaction being designated as an irrevocable transaction; and

not updating the meta-data location before the transactional read from the transaction in response to the transaction not being designated as an irrevocable transaction.

8. The machine readable medium of claim 7, wherein a transaction descriptor is to be associated with the transaction, and wherein at least a portion of the read and write locked value associated with the transaction includes a reference to the first transaction descriptor, and at least a portion of the read value includes a reference to a version number.

9. The machine readable medium of claim 7, wherein the program code which when executed by the machine, is further to cause the machine to perform the operations of:

updating the meta-data location to the unlocked value from the read and write locked value or the read locked value in response to a commit or an abort of the transaction.

10. The machine readable medium of claim 7, wherein the program code which when executed by the machine, is further to cause the machine to perform the operations of:

performing a conflict resolution between the transaction and the remote transaction upon an attempt to update the meta-data location before performing a transactional access to the data object from the transaction when the meta-data value includes a read and write locked value associated with a remote transaction, wherein the transaction is given priority over the remote transaction in response to the transaction being designated an irrevocable transaction.

11. The machine readable medium of claim 10, wherein the program code which when executed by the machine, is further to cause the machine to perform the operations of:

selecting one of the transaction and the remote transaction to continue as an irrevocable transaction in response to the transaction being designated as an irrevocable transaction and the remote transaction encountering an irrevocable event.