Linux synchronization Review

Up and SMP

Linux Kernel control path

Up vs SMP

API

Common control path:

ISR

Softirq/tasklet: BH

The preceding two cannot be context switches.

Exception/System Call: from user to Kernel

Setup Cr to solve

R/W lock?

Sequence_lock?

Big Table?

CPU need hw support for Cr

For x86, cmpxchg, compare, exchange

For arm test_set instruction

The smaller the CR, the better.

For Singel core, yield CPU is supported. Therefore, the control path must be a normal path and can be preempt

When entering from the spin_lock, The kpath must be unique so that it is not easy to deadlock and should not be interrupted. SMP must be the same as up.

Almost all sync API combine with disable_irq/softirq/preempt_ex

Spin_lock call arch_spin_lock?

For multicore exclusive instruction, ensure atomic

Read-check-Cr (test)

For SMP, lock_break is used