Day59 Lab — pthread Condition Variable

Objective

Understand synchronization based on condition variables.

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Architecture

Producer

↓

Queue

↓

Consumer

Synchronization:

• mutex
• not_empty
• not_full

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Experiment 1

Minimal wait/signal.

Verify:

• cond_wait
• predicate loop

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Experiment 2

Spurious wakeup.

Send signal without changing predicate.

Observe:

worker wakeup

↓

worker returns to wait

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Experiment 3

Single item producer consumer.

Shared state:

bool has_item;
int item;

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Experiment 4

Bounded queue.

Shared state:

count
head
tail

Conditions:

not_empty
not_full

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Experiment 5

Timed wait.

Use:

pthread_cond_timedwait()

Observe:

timeout returns ETIMEDOUT.

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Experiment 6

Multi consumer.

Compare:

signal
vs
broadcast

Observe:

broadcast wakes all waiters.

Only one may proceed.

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Result

Condition variable is suitable for:

• state machine
• daemon
• worker pool
• event-driven systems