blob: 72eceed32bcefa187e931c371c888dfb91fd9b7a (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
|
#include <pthread.h>
#include "linux/preempt.h"
/*
* In userspace, pthreads are preemptible and can migrate CPUs at any time.
*
* In the kernel, preempt_disable() logic essentially guarantees that a marked
* critical section owns its CPU for the relevant block. This is necessary for
* various code paths, critically including the percpu system as it allows for
* non-atomic reads and writes to CPU-local data structures.
*
* The high performance userspace equivalent would be to use thread local
* storage to replace percpu data, but that would be complicated. It should be
* correct to instead guarantee mutual exclusion for the critical sections.
*/
static pthread_mutex_t preempt_lock;
__attribute__((constructor))
static void preempt_init(void) {
pthread_mutexattr_t attr;
pthread_mutexattr_init(&attr);
pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
pthread_mutex_init(&preempt_lock, &attr);
pthread_mutexattr_destroy(&attr);
}
void preempt_disable(void)
{
pthread_mutex_lock(&preempt_lock);
}
void preempt_enable(void)
{
pthread_mutex_unlock(&preempt_lock);
}
|