These changes are the raw update to linux-4.4.6-rt14. Kernel sources

[kvmfornfv.git] / kernel / Documentation / RCU / whatisRCU.txt

diff --git a/kernel/Documentation/RCU/whatisRCU.txt b/kernel/Documentation/RCU/whatisRCU.txt
index 88dfce1..dc49c67 100644 (file)
--- a/kernel/Documentation/RCU/whatisRCU.txt
+++ b/kernel/Documentation/RCU/whatisRCU.txt
@@ -256,7 +256,9 @@ rcu_dereference()
        If you are going to be fetching multiple fields from the
        RCU-protected structure, using the local variable is of
        course preferred.  Repeated rcu_dereference() calls look
-       ugly and incur unnecessary overhead on Alpha CPUs.
+       ugly, do not guarantee that the same pointer will be returned
+       if an update happened while in the critical section, and incur
+       unnecessary overhead on Alpha CPUs.
 
        Note that the value returned by rcu_dereference() is valid
        only within the enclosing RCU read-side critical section.
@@ -362,7 +364,7 @@ uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
        };
        DEFINE_SPINLOCK(foo_mutex);
 
-       struct foo *gbl_foo;
+       struct foo __rcu *gbl_foo;
 
        /*
         * Create a new struct foo that is the same as the one currently
@@ -384,7 +386,7 @@ uses of RCU may be found in listRCU.txt, arrayRCU.txt, and NMI-RCU.txt.
 
                new_fp = kmalloc(sizeof(*new_fp), GFP_KERNEL);
                spin_lock(&foo_mutex);
-               old_fp = gbl_foo;
+               old_fp = rcu_dereference_protected(gbl_foo, lockdep_is_held(&foo_mutex));
                *new_fp = *old_fp;
                new_fp->a = new_a;
                rcu_assign_pointer(gbl_foo, new_fp);
@@ -485,7 +487,7 @@ The foo_update_a() function might then be written as follows:
 
                new_fp = kmalloc(sizeof(*new_fp), GFP_KERNEL);
                spin_lock(&foo_mutex);
-               old_fp = gbl_foo;
+               old_fp = rcu_dereference_protected(gbl_foo, lockdep_is_held(&foo_mutex));
                *new_fp = *old_fp;
                new_fp->a = new_a;
                rcu_assign_pointer(gbl_foo, new_fp);
@@ -879,11 +881,9 @@ SRCU:      Initialization/cleanup
 
 All:  lockdep-checked RCU-protected pointer access
 
-       rcu_access_index
        rcu_access_pointer
-       rcu_dereference_index_check
        rcu_dereference_raw
-       rcu_lockdep_assert
+       RCU_LOCKDEP_WARN
        rcu_sleep_check
        RCU_NONIDLE