Rich Felker
6016457011
this implementation is rather heavy-weight, but it's the first solution i've found that's actually correct. all waiters actually wait twice at the barrier so that they can synchronize exit, and they hold a "vm lock" that prevents changes to virtual memory mappings (and blocks pthread_barrier_destroy) until all waiters are finished inspecting the barrier. thus, it is safe for any thread to destroy and/or unmap the barrier's memory as soon as pthread_barrier_wait returns, without further synchronization.
21 lines
374 B
C
21 lines
374 B
C
#include <unistd.h>
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#include <sys/mman.h>
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#include "syscall.h"
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#include "libc.h"
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static void dummy1(int x) { }
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static void dummy0(void) { }
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weak_alias(dummy1, __vm_lock);
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weak_alias(dummy0, __vm_unlock);
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int __munmap(void *start, size_t len)
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{
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int ret;
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__vm_lock(-1);
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ret = syscall(SYS_munmap, start, len);
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__vm_unlock();
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return ret;
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}
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weak_alias(__munmap, munmap);
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