Linux Kernel Memory Barriers & RCU

When to use

• Writing or reviewing kernel code that shares memory between CPUs, interrupts, or workqueue/process contexts (sysfs attributes, seqlocks, RCU data structures, flag+payload protocols).
• Deciding between spinlock, RCU, and atomic/RMW for a given data structure.
• Debugging "works on my machine but corrupts under SMP" symptoms or lockdep / KCSAN / "sleeping function called from invalid context" splats.
• Explaining why a patch needs READ_ONCE/WRITE_ONCE, a barrier, or rcu_dereference where a plain access was used.

When not to use