runtime/dyninst/probe_lock.h - systemtap

Data types defined

Functions defined

Macros defined

Source code

/* dyninst probe locking header file
* Copyright (C) 2012 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 _STAPDYN_PROBE_LOCK_H
‌#define _STAPDYN_PROBE_LOCK_H

#include <pthread.h>

‌struct stp_probe_lock {
    #ifdef STP_TIMING
    atomic_t *skipped;
    #endif
    pthread_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;) {
        pthread_rwlock_unlock(locks[i].lock);
    }
}

static unsigned
‌stp_lock_probe(const struct stp_probe_lock *locks, unsigned num_locks)
{
#if 0 // XXX: should we bother with trylocks in pure userspace?
    unsigned i, retries = 0;
    for (i = 0; i < num_locks; ++i) {
        if (locks[i].write_p)
            while (!pthread_rwlock_trywrlock(locks[i].lock)) {
#if !define(STAP_SUPRESS_TIME_LIMITS_ENABLE)
                if (++retries > MAXTRYLOCK)
                    goto skip;
#endif
                udelay (TRYLOCKDELAY);
            }
        else
            while (!pthread_rwlock_tryrdlock(locks[i].lock)) {
#if !define(STAP_SUPPRESS_TIME_LIMITS_ENABLE)
                if (++retries > MAXTRYLOCK)
                    goto skip;
#endif
                udelay (TRYLOCKDELAY);
            }
    }
    return 1;

skip:
    atomic_inc(skipped_count());
#ifdef STP_TIMING
    atomic_inc(locks[i].skipped);
#endif
    stp_unlock_probe(locks, i);
    return 0;
#else
    unsigned i;
    for (i = 0; i < num_locks; ++i) {
        if (locks[i].write_p)
            pthread_rwlock_wrlock(locks[i].lock);
        else
            pthread_rwlock_rdlock(locks[i].lock);
    }
    return 1;
#endif
}

#endif /* _STAPDYN_PROBE_LOCK_H */