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ff4d082246
This is part of the userspace implementation of the kernel APIs for bcachefs-tools. The previous implementation just provided a barrier, but this isn't sufficient to make the associated percpu implementation safe. Signed-off-by: Justin Husted <sigstop@gmail.com>
29 lines
882 B
C
29 lines
882 B
C
#include <pthread.h>
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#include "linux/preempt.h"
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/*
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* In userspace, pthreads are preemptible and can migrate CPUs at any time.
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*
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* In the kernel, preempt_disable() logic essentially guarantees that a marked
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* critical section owns its CPU for the relevant block. This is necessary for
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* various code paths, critically including the percpu system as it allows for
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* non-atomic reads and writes to CPU-local data structures.
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*
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* The high performance userspace equivalent would be to use thread local
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* storage to replace percpu data, but that would be complicated. It should be
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* correct to instead guarantee mutual exclusion for the critical sections.
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*/
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static pthread_mutex_t preempt_lock = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
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void preempt_disable(void)
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{
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pthread_mutex_lock(&preempt_lock);
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}
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void preempt_enable(void)
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{
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pthread_mutex_unlock(&preempt_lock);
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}
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