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rcu: Remove SPARSE_RCU_POINTER Kconfig option

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The sparse-based checking for non-RCU accesses to RCU-protected pointers
has been around for a very long time, and it is now the only type of
sparse-based checking that is optional.  This commit therefore makes
it unconditional.

Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
This commit is contained in:
Paul E. McKenney
2017-05-12 15:56:35 -07:00
parent c4a09ff752
commit 41a2901e7d
7 changed files with 7 additions and 42 deletions
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9
Documentation/RCU/Design/Requirements/Requirements.html
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@@ -559,9 +559,7 @@ The <tt>rcu_access_pointer()</tt> on line&nbsp;6 is similar to
For <tt>remove_gp_synchronous()</tt>, as long as all modifications
to <tt>gp</tt> are carried out while holding <tt>gp_lock</tt>,
the above optimizations are harmless.
However,
with <tt>CONFIG_SPARSE_RCU_POINTER=y</tt>,
<tt>sparse</tt> will complain if you
However, <tt>sparse</tt> will complain if you
define <tt>gp</tt> with <tt>__rcu</tt> and then
access it without using
either <tt>rcu_access_pointer()</tt> or <tt>rcu_dereference()</tt>.
@@ -1978,9 +1976,8 @@ guard against mishaps and misuse:
and <tt>rcu_dereference()</tt>, perhaps (incorrectly)
substituting a simple assignment.
To catch this sort of error, a given RCU-protected pointer may be
tagged with <tt>__rcu</tt>, after which running sparse
with <tt>CONFIG_SPARSE_RCU_POINTER=y</tt> will complain
about simple-assignment accesses to that pointer.
tagged with <tt>__rcu</tt>, after which sparse
will complain about simple-assignment accesses to that pointer.
Arnd Bergmann made me aware of this requirement, and also
supplied the needed
<a href="https://lwn.net/Articles/376011/">patch series</a>.