US 5,845,130 A · Mailbox traffic controller

Abstract

A system and method for preventing contention in a shared memory environment. In one embodiment, a first processor reads a traffic controller which is coupled to a shared memory and to a second processor. The first processor writes its identifier into the traffic controller provided that the traffic controller does not already have an identifier corresponding to the second processor stored therein. If the traffic controller does have an identifier corresponding to the second processor stored therein, the first processor periodically reads the traffic controller until the traffic controller does not have an identifier corresponding to the second processor stored therein. Once the traffic controller has the identifier corresponding to the first processor stored therein, the traffic controller allows the first processor to control access to the shared memory. Once the first processor controls access to the shared memory, the second processor knows that it must wait before attempting to control access to the shared memory. In so doing, the present invention eliminates contention between the first and second processors for control of the shared memory.

Claims15

Dependent claims

An apparatus for efficiently sharing memory between two processors in a peripheral component interconnect (PCI) environment comprising:

a first processor coupled to a PCI bus,
a shared memory coupled to said PCI bus,
a second processor coupled to said shared memory,
a traffic controller coupled to said first processor and said second processor, said traffic controller adapted to indicate to said first and second processors when one of said first and second processors is controlling access to said shared memory such that the other of said first and second processors waits to attempt to control access to said shared memory thereby preventing contention between said first and second processors for control of said shared memory, said traffic controller configured such that when one of said first and second processors is controlling access to said shared memory, the other of said first and second processors can still access said shared memory if permitted by said one of said first and second processors controlling access to said shared memory.

1 more element

A method for preventing contention in a shared memory environment comprising the steps of:

a) having a first processor read a traffic controller coupled to a shared memory to determine whether said shared memory is available to be controlled by said first processor,
b) writing an identifier corresponding to said first processor into said traffic controller provided said traffic controller does not have an identifier corresponding to said second processor stored therein,
c) preventing said second processor from controlling said shared memory once said identifier corresponding to said first identifier is stored therein,
d) allowing said second processor to access said shared memory even when access to said shared memory is controlled by said first processor if said first processor permits said second processor to access said shared memory;
and
e) removing said identifier corresponding to said first processor from said traffic controller when said first processor no longer desires control of said shared memory such that said shared memory is accessible and controlled by said second processor if desired.

3 more elements

Dependencies are inferred from the claim text.

Mailbox traffic controller

Life of this patent

Mailbox traffic controller

Life of this patent

Abstract

Claims15