sched: tasks: Use sequence counter with associated spinlock (b7505861) · Commits · 戴 / test

A sequence counter write side critical section must be protected by some form of locking to serialize writers. A plain seqcount_t does not contain the information of which lock must be held when entering a write side critical section. Use the new seqcount_spinlock_t data type, which allows to associate a spinlock with the sequence counter. This enables lockdep to verify that the spinlock used for writer serialization is held when the write side critical section is entered. If lockdep is disabled this lock association is compiled out and has neither storage size nor runtime overhead. Signed-off-by:

Ahmed S. Darwish <a.darwish@linutronix.de> Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200720155530.1173732-14-a.darwish@linutronix.de

include/linux/sched.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -1050,7 +1050,7 @@ struct task_struct {
		/* Protected by ->alloc_lock: */
		nodemask_t mems_allowed;
		/* Seqence number to catch updates: */
		seqcount_t mems_allowed_seq;
		seqcount_spinlock_t mems_allowed_seq;
		int cpuset_mem_spread_rotor;
		int cpuset_slab_spread_rotor;
		#endif

init/init_task.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -154,7 +154,8 @@ struct task_struct init_task
		.trc_holdout_list = LIST_HEAD_INIT(init_task.trc_holdout_list),
		#endif
		#ifdef CONFIG_CPUSETS
		.mems_allowed_seq = SEQCNT_ZERO(init_task.mems_allowed_seq),
		.mems_allowed_seq = SEQCNT_SPINLOCK_ZERO(init_task.mems_allowed_seq,
		&init_task.alloc_lock),
		#endif
		#ifdef CONFIG_RT_MUTEXES
		.pi_waiters = RB_ROOT_CACHED,

kernel/fork.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -2032,7 +2032,7 @@ static __latent_entropy struct task_struct *copy_process(
		#ifdef CONFIG_CPUSETS
		p->cpuset_mem_spread_rotor = NUMA_NO_NODE;
		p->cpuset_slab_spread_rotor = NUMA_NO_NODE;
		seqcount_init(&p->mems_allowed_seq);
		seqcount_spinlock_init(&p->mems_allowed_seq, &p->alloc_lock);
		#endif
		#ifdef CONFIG_TRACE_IRQFLAGS
		p->irq_events = 0;

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