runtime/linux/probe_lock.h - systemtap

Data types defined

Functions defined

Macros defined

Source code

/* probe locking header file
 * Copyright (C) 2009-2010 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 _STAPLINUX_PROBE_LOCK_H
‌#define _STAPLINUX_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 !defined(STAP_SUPPRESS_TIME_LIMITS_ENABLE)
                if (++retries > MAXTRYLOCK)
                    goto skip;
#endif
                udelay (TRYLOCKDELAY);
            }
        else
            while (!read_trylock(locks[i].lock)) {
#if !defined(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;
}


#endif /* _STAPLINUX_PROBE_LOCK_H */