System and method for reducing synchronization overhead in multithreaded code

A computer program product for use in conjunction with a computer system, the computer program product comprising a computer readable storage medium and a computer program mechanism embedded therein, the computer program mechanism comprising:

• a mutex control procedure for controlling a request from a requesting thread to acquire a target mutex, said target mutex capable of specifying a first synchronization mode, a second synchronization mode, and a thread that is associated with said target mutex even when the target mutex is not held by any thread, the mutex control procedure including instructions for:
• receiving a request to acquire said target mutex from a requesting thread;
• (a) when said target mutex is in said first synchronization mode, and wherein:
• (i) when said requesting thread is the thread associated with said target mutex, said request to acquire said target mutex is granted without using atomic instructions to assure that no thread is operating on said target mutex;
• and
• (ii) when said requesting thread is not the thread associated with said target mutex, verging that no thread is operating on said target mutex;
• (b) when said target mutex is in said second synchronization mode, assuring, with atomic machine instructions, that no thread is operating on said target mutex;
• and granting said request to acquire said target mutex.

A computer system for controlling acquisition of a target mutex that is capable of specifying a first synchronization mode, a second synchronization mode, and a thread associated with said target mutex, the computer system comprising:

• at least one central processing unit;
• a memory;
• at least one bus connecting the at least one central processing unit and the memory;
• and
• at least one thread, including a requesting thread;
• the memory including a mutex controller and said target mutex;
• wherein said mutex controller includes instructions for:
• determining, in response to a request to acquire said target mutex by said requesting thread, whether said target mutex is in said first synchronization modeor said second synchronization mode;
• and
• (a) when said target mutex is in said first synchronization mode, said mutex controller queries whether said requesting thread is the thread associated with said target mutex, and, in response to said query:
• (i) grants said request to acquire said target mutex when said requesting thread is the thread associated with said target mutex without using atomic instructions to ensure that no other thread is holding said mutex;
• and
• (ii) performs a verification procedure that ensures that no thread is operating on said target mutex when said requesting thread is not the thread associated with said target mutex;
• and
• (b) when said target mutex is in said second synchronization mode, said mutex controller ensures, with atomic machine instructions, that no thread is operating on said target mutex and grants said request to acquire said target mutex;
• wherein said thread associated with said target mutex is associated with said target mutex even when said target mutex is not held by any thread.

A computer program product for use in conjunction with a computer system, the computer program product comprising a computer readable storage medium and a computer program mechanism embedded therein, the computer program mechanism comprising a mutex control procedure for controlling a request from a requesting thread to acquire a target mutex capable of specifying a thread associated with said target mutex, the mutex control procedure including instructions for:

• querying, without use of atomic machine instructions, whether said requesting thread is the thread associated with said target mutex;
• verifying that no thread is operating on said target mutex;
• and
• granting said request to acquire said target mutex;
• wherein said associated thread being associated with said target mutex even when no thread holds the target mutex.

A computer system for controlling acquisition of a target mutex capable of specifying a thread associated with said target mutex, the computer system comprising:

• at least one central processing unit;
• a memory;
• at least one bus connecting the at least one central processing unit and the memory;
• and
• at least one thread, including a requesting thread;
• the memory including a mutex controller and said target mutex;
• wherein said mutex controller includes instructions for:
• determining, in response to a request to acquire said target mutex by said requesting thread, whether said requesting thread is the thread associated with said target mutex, and, in response to said request:
• (i) granting said request to acquire said target mutex when said requesting thread is the thread associated with said target mutex;
• and
• (ii) performing a verification procedure that ensures that no thread is operating on said target mutex when said requesting thread is not the thread associated with said target mutex;
• wherein said associated thread being associated with said target mutex even when no thread holds the target mutex.

A computer system, comprising:

• a CPU;
• and
• memory coupled to said CPU, said memory storing a mutex usable to provide controlled access to a resource, said mutex programmed to specify one of a plurality of synchronization techniques related to using said mutex among multiple threads;
• wherein said CPU is adapted to program said mutex from one synchronization technique to another synchronization technique;
• wherein a thread is associated with the mutex even if no thread owns the mutex and wherein one of the synchronization techniques uses atomic operations and, when the associated thread requests the mutex, another synchronization does not use atomic operation.