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Table of Minimum Spin Lock Requirements

The following table lists the minimum locking requirements between various contexts. In some cases, the same context can only be running on one CPU at a time, so no locking is required for that context (eg. a particular thread can only run on one CPU at a time, but if it needs shares data with another thread, locking is required).

Remember the advice above: you can always use spin_lock_irqsave(), which is a superset of all other spinlock primitives.

	IRQ Handler A	IRQ Handler B	Softirq A	Softirq B	Tasklet A	Tasklet B	Timer A	Timer B	User Context A	User Context B
IRQ Handler A	None
IRQ Handler B	spin_lock_irqsave	None
Softirq A	spin_lock_irq	spin_lock_irq	spin_lock
Softirq B	spin_lock_irq	spin_lock_irq	spin_lock	spin_lock
Tasklet A	spin_lock_irq	spin_lock_irq	spin_lock	spin_lock	None
Tasklet B	spin_lock_irq	spin_lock_irq	spin_lock	spin_lock	spin_lock	None
Timer A	spin_lock_irq	spin_lock_irq	spin_lock	spin_lock	spin_lock	spin_lock	None
Timer B	spin_lock_irq	spin_lock_irq	spin_lock	spin_lock	spin_lock	spin_lock	spin_lock	None
User Context A	spin_lock_irq	spin_lock_irq	spin_lock_bh	spin_lock_bh	spin_lock_bh	spin_lock_bh	spin_lock_bh	spin_lock_bh	None
User Context B	spin_lock_irq	spin_lock_irq	spin_lock_bh	spin_lock_bh	spin_lock_bh	spin_lock_bh	spin_lock_bh	spin_lock_bh	down_interruptible	None

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Table of Contents

Table of Minimum Spin Lock Requirements