rcu: Remove SPARSE_RCU_POINTER Kconfig option
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>hifive-unleashed-5.1
Paul E. McKenney
parent
c4a09ff752
commit
41a2901e7d
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@ -559,9 +559,7 @@ The <tt>rcu_access_pointer()</tt> on line 6 is similar to
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For <tt>remove_gp_synchronous()</tt>, as long as all modifications
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to <tt>gp</tt> are carried out while holding <tt>gp_lock</tt>,
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the above optimizations are harmless.
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However,
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with <tt>CONFIG_SPARSE_RCU_POINTER=y</tt>,
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<tt>sparse</tt> will complain if you
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However, <tt>sparse</tt> will complain if you
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define <tt>gp</tt> with <tt>__rcu</tt> and then
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access it without using
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either <tt>rcu_access_pointer()</tt> or <tt>rcu_dereference()</tt>.
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@ -1978,9 +1976,8 @@ guard against mishaps and misuse:
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and <tt>rcu_dereference()</tt>, perhaps (incorrectly)
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substituting a simple assignment.
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To catch this sort of error, a given RCU-protected pointer may be
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tagged with <tt>__rcu</tt>, after which running sparse
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with <tt>CONFIG_SPARSE_RCU_POINTER=y</tt> will complain
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about simple-assignment accesses to that pointer.
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tagged with <tt>__rcu</tt>, after which sparse
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will complain about simple-assignment accesses to that pointer.
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Arnd Bergmann made me aware of this requirement, and also
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supplied the needed
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<a href="https://lwn.net/Articles/376011/">patch series</a>.
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@ -413,11 +413,11 @@ over a rather long period of time, but improvements are always welcome!
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read-side critical sections. It is the responsibility of the
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RCU update-side primitives to deal with this.
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17. Use CONFIG_PROVE_RCU, CONFIG_DEBUG_OBJECTS_RCU_HEAD, and the
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__rcu sparse checks (enabled by CONFIG_SPARSE_RCU_POINTER) to
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validate your RCU code. These can help find problems as follows:
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17. Use CONFIG_PROVE_LOCKING, CONFIG_DEBUG_OBJECTS_RCU_HEAD, and the
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__rcu sparse checks to validate your RCU code. These can help
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find problems as follows:
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CONFIG_PROVE_RCU: check that accesses to RCU-protected data
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CONFIG_PROVE_LOCKING: check that accesses to RCU-protected data
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structures are carried out under the proper RCU
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read-side critical section, while holding the right
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combination of locks, or whatever other conditions
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@ -103,9 +103,3 @@ have already built it.
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The optional make variable CF can be used to pass arguments to sparse. The
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build system passes -Wbitwise to sparse automatically.
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Checking RCU annotations
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~~~~~~~~~~~~~~~~~~~~~~~~
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RCU annotations are not checked by default. To enable RCU annotation
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checks, include -DCONFIG_SPARSE_RCU_POINTER in your CF flags.
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@ -17,11 +17,7 @@
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# define __release(x) __context__(x,-1)
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# define __cond_lock(x,c) ((c) ? ({ __acquire(x); 1; }) : 0)
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# define __percpu __attribute__((noderef, address_space(3)))
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#ifdef CONFIG_SPARSE_RCU_POINTER
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# define __rcu __attribute__((noderef, address_space(4)))
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#else /* CONFIG_SPARSE_RCU_POINTER */
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# define __rcu
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#endif /* CONFIG_SPARSE_RCU_POINTER */
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# define __private __attribute__((noderef))
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extern void __chk_user_ptr(const volatile void __user *);
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extern void __chk_io_ptr(const volatile void __iomem *);
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@ -1306,21 +1306,6 @@ menu "RCU Debugging"
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config PROVE_RCU
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def_bool PROVE_LOCKING
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config SPARSE_RCU_POINTER
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bool "RCU debugging: sparse-based checks for pointer usage"
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default n
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help
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This feature enables the __rcu sparse annotation for
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RCU-protected pointers. This annotation will cause sparse
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to flag any non-RCU used of annotated pointers. This can be
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helpful when debugging RCU usage. Please note that this feature
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is not intended to enforce code cleanliness; it is instead merely
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a debugging aid.
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Say Y to make sparse flag questionable use of RCU-protected pointers
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Say N if you are unsure.
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config TORTURE_TEST
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tristate
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default n
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@ -25,9 +25,6 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
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earlycpio.o seq_buf.o siphash.o \
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nmi_backtrace.o nodemask.o win_minmax.o
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CFLAGS_radix-tree.o += -DCONFIG_SPARSE_RCU_POINTER
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CFLAGS_idr.o += -DCONFIG_SPARSE_RCU_POINTER
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lib-$(CONFIG_MMU) += ioremap.o
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lib-$(CONFIG_SMP) += cpumask.o
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lib-$(CONFIG_DMA_NOOP_OPS) += dma-noop.o
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@ -74,10 +74,6 @@ CONFIG_TINY_RCU
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These are controlled by CONFIG_PREEMPT and/or CONFIG_SMP.
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CONFIG_SPARSE_RCU_POINTER
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Makes sense only for sparse runs, not for kernel builds.
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CONFIG_SRCU
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CONFIG_TASKS_RCU
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