Doug / smarc-fsl-linux-kernel

25 Feb, 2010

1 commit

  • 632ee2001   rcu: Introduce lockdep-based checking to RCU read-side primitives ... Browse Code »

    Inspection is proving insufficient to catch all RCU misuses,
    which is understandable given that rcu_dereference() might be
    protected by any of four different flavors of RCU (RCU, RCU-bh,
    RCU-sched, and SRCU), and might also/instead be protected by any
    of a number of locking primitives. It is therefore time to
    enlist the aid of lockdep.

    This set of patches is inspired by earlier work by Peter
    Zijlstra and Thomas Gleixner, and takes the following approach:

    o Set up separate lockdep classes for RCU, RCU-bh, and RCU-sched.

    o Set up separate lockdep classes for each instance of SRCU.

    o Create primitives that check for being in an RCU read-side
    critical section. These return exact answers if lockdep is
    fully enabled, but if unsure, report being in an RCU read-side
    critical section. (We want to avoid false positives!)
    The primitives are:

    For RCU: rcu_read_lock_held(void)

    For RCU-bh: rcu_read_lock_bh_held(void)

    For RCU-sched: rcu_read_lock_sched_held(void)

    For SRCU: srcu_read_lock_held(struct srcu_struct *sp)

    o Add rcu_dereference_check(), which takes a second argument
    in which one places a boolean expression based on the above
    primitives and/or lockdep_is_held().

    o A new kernel configuration parameter, CONFIG_PROVE_RCU, enables
    rcu_dereference_check(). This depends on CONFIG_PROVE_LOCKING,
    and should be quite helpful during the transition period while
    CONFIG_PROVE_RCU-unaware patches are in flight.

    The existing rcu_dereference() primitive does no checking, but
    upcoming patches will change that.

    Signed-off-by: Paul E. McKenney
    Cc: laijs@cn.fujitsu.com
    Cc: dipankar@in.ibm.com
    Cc: mathieu.desnoyers@polymtl.ca
    Cc: josh@joshtriplett.org
    Cc: dvhltc@us.ibm.com
    Cc: niv@us.ibm.com
    Cc: peterz@infradead.org
    Cc: rostedt@goodmis.org
    Cc: Valdis.Kletnieks@vt.edu
    Cc: dhowells@redhat.com
    LKML-Reference:
    Signed-off-by: Ingo Molnar

    Paul E. McKenney
     

12 Apr, 2009

1 commit

  • 9eeba6138   lockdep: warn about lockdep disabling after kernel taint ... Browse Code »

    Impact: provide useful missing info for developers

    Kernel taint can occur in several situations such as warnings,
    load of prorietary or staging modules, bad page, etc...

    But when such taint happens, a developer might still be working on
    the kernel, expecting that lockdep is still enabled. But a taint
    disables lockdep without ever warning about it.
    Such a kernel behaviour doesn't really help for kernel development.

    This patch adds this missing warning.

    Since the taint is done most of the time after the main message that
    explain the real source issue, it seems safe to warn about it inside
    add_taint() so that it appears at last, without hurting the main
    information.

    v2: Use a generic helper to disable lockdep instead of an
    open coded xchg().

    Signed-off-by: Frederic Weisbecker
    Cc: Peter Zijlstra
    LKML-Reference:
    Signed-off-by: Ingo Molnar

    Frederic Weisbecker
     

01 Aug, 2008

1 commit

04 Jul, 2006

1 commit

  • 9a11b49a8   [PATCH] lockdep: better lock debugging ... Browse Code »

    Generic lock debugging:

    - generalized lock debugging framework. For example, a bug in one lock
    subsystem turns off debugging in all lock subsystems.

    - got rid of the caller address passing (__IP__/__IP_DECL__/etc.) from
    the mutex/rtmutex debugging code: it caused way too much prototype
    hackery, and lockdep will give the same information anyway.

    - ability to do silent tests

    - check lock freeing in vfree too.

    - more finegrained debugging options, to allow distributions to
    turn off more expensive debugging features.

    There's no separate 'held mutexes' list anymore - but there's a 'held locks'
    stack within lockdep, which unifies deadlock detection across all lock
    classes. (this is independent of the lockdep validation stuff - lockdep first
    checks whether we are holding a lock already)

    Here are the current debugging options:

    CONFIG_DEBUG_MUTEXES=y
    CONFIG_DEBUG_LOCK_ALLOC=y

    which do:

    config DEBUG_MUTEXES
    bool "Mutex debugging, basic checks"

    config DEBUG_LOCK_ALLOC
    bool "Detect incorrect freeing of live mutexes"

    Signed-off-by: Ingo Molnar
    Signed-off-by: Arjan van de Ven
    Signed-off-by: Andrew Morton
    Signed-off-by: Linus Torvalds

    Ingo Molnar