Messages in this thread Patch in this message | | | Date | Tue, 4 Oct 2011 23:03:29 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH tip/core/rcu 53/55] rcu: Warn when srcu_read_lock() is used in an extended quiescent state |
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On Tue, Sep 06, 2011 at 11:00:47AM -0700, Paul E. McKenney wrote: > Catch SRCU up to the other variants of RCU by making PROVE_RCU > complain if either srcu_read_lock() or srcu_read_lock_held() are > used from within dyntick-idle mode. > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > --- > include/linux/srcu.h | 25 +++++++++++++++---------- > 1 files changed, 15 insertions(+), 10 deletions(-) > > diff --git a/include/linux/srcu.h b/include/linux/srcu.h > index 58971e8..fcbaee7 100644 > --- a/include/linux/srcu.h > +++ b/include/linux/srcu.h > @@ -28,6 +28,7 @@ > #define _LINUX_SRCU_H > > #include <linux/mutex.h> > +#include <linux/rcupdate.h> > > struct srcu_struct_array { > int c[2]; > @@ -60,18 +61,10 @@ int __init_srcu_struct(struct srcu_struct *sp, const char *name, > __init_srcu_struct((sp), #sp, &__srcu_key); \ > }) > > -# define srcu_read_acquire(sp) \ > - lock_acquire(&(sp)->dep_map, 0, 0, 2, 1, NULL, _THIS_IP_) > -# define srcu_read_release(sp) \ > - lock_release(&(sp)->dep_map, 1, _THIS_IP_) > - > #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ > > int init_srcu_struct(struct srcu_struct *sp); > > -# define srcu_read_acquire(sp) do { } while (0) > -# define srcu_read_release(sp) do { } while (0) > - > #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ > > void cleanup_srcu_struct(struct srcu_struct *sp); > @@ -90,11 +83,23 @@ long srcu_batches_completed(struct srcu_struct *sp); > * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, > * this assumes we are in an SRCU read-side critical section unless it can > * prove otherwise. > + * > + * Note that if the CPU is in an extended quiescent state, for example, > + * if the CPU is in dyntick-idle mode, then rcu_read_lock_held() returns > + * false even if the CPU did an rcu_read_lock(). The reason for this is > + * that RCU ignores CPUs that are in extended quiescent states, so such > + * a CPU is effectively never in an RCU read-side critical section > + * regardless of what RCU primitives it invokes. This state of affairs > + * is required -- RCU would otherwise need to periodically wake up > + * dyntick-idle CPUs, which would defeat the whole purpose of dyntick-idle > + * mode. > */ > static inline int srcu_read_lock_held(struct srcu_struct *sp) > { > if (debug_locks) > return lock_is_held(&sp->dep_map); > + if (rcu_check_extended_qs()) > + return 0;
Just to warn you, While rebasing this, I'm also moving things around:
if (!debug_lock) return 1;
if (rcu_is_cpu_idle()) return 0;
return lock_is_held(&sp->dep_map);
Otherwise we only do the check if lock debugging is disabled, which is not what we want I think.
> return 1; > } > > @@ -150,7 +155,7 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) > { > int retval = __srcu_read_lock(sp); > > - srcu_read_acquire(sp); > + rcu_lock_acquire(&(sp)->dep_map); > return retval; > } > > @@ -164,7 +169,7 @@ static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) > static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) > __releases(sp) > { > - srcu_read_release(sp); > + rcu_lock_release(&(sp)->dep_map); > __srcu_read_unlock(sp, idx); > } > > -- > 1.7.3.2 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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