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/* probe locking header file
* Copyright (C) 2009 Red Hat Inc.
*
* This file is part of systemtap, and is free software. You can
* redistribute it and/or modify it under the terms of the GNU General
* Public License (GPL); either version 2, or (at your option) any
* later version.
*/
#ifndef _PROBE_LOCK_H
#define _PROBE_LOCK_H
#include <linux/spinlock.h>
// XXX: old 2.6 kernel hack
#ifndef read_trylock
#define read_trylock(x) ({ read_lock(x); 1; })
#endif
struct stp_probe_lock {
#ifdef STP_TIMING
atomic_t *skipped;
#endif
rwlock_t *lock;
unsigned write_p;
};
static void
stp_unlock_probe(const struct stp_probe_lock *locks, unsigned num_locks)
{
unsigned i;
for (i = num_locks; i-- > 0;) {
if (locks[i].write_p)
write_unlock(locks[i].lock);
else
read_unlock(locks[i].lock);
}
}
static unsigned
stp_lock_probe(const struct stp_probe_lock *locks, unsigned num_locks)
{
unsigned i, retries = 0;
for (i = 0; i < num_locks; ++i) {
if (locks[i].write_p)
while (!write_trylock(locks[i].lock)) {
if (++retries > MAXTRYLOCK)
goto skip;
ndelay (TRYLOCKDELAY);
}
else
while (!read_trylock(locks[i].lock)) {
if (++retries > MAXTRYLOCK)
goto skip;
ndelay (TRYLOCKDELAY);
}
}
return 1;
skip:
atomic_inc(&skipped_count);
#ifdef STP_TIMING
atomic_inc(locks[i].skipped);
#endif
stp_unlock_probe(locks, i);
return 0;
}
#endif /* _PROBE_LOCK_H */
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