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cpthreads
Mati Ur Rahman
Mati Ur Rahman

Reputation: 11

Pthread Synchronization Issue

What if all threads read a global variable which was assigned a value by the main() prior to the creation of the threads. Do we need any Mutex for synchronization?

Upvotes: 1

Views: 67

Answers (3)

Nanc
Nanc

Reputation: 464

If any of the threads wants to change the value of your global variable then yes, you need a new mutex. Otherwise no synchronization is needed.

Upvotes: 0

Kerrek SB
Kerrek SB

Reputation: 477040

No.

A data race happens when multiple threads access a memory location (through a non-atomic value) and at least one of the accesses is a write and the operations are not ordered.

Since thread creation is a synchronization point, all the accesses after thread creation are ordered after the initial write access, and the later accesses are only reads. So there is no race.

Upvotes: 1

kwierman
kwierman

Reputation: 461

For reading the variable: no

For writing to and reading the variable: yes

Upvotes: 1

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