linux-stable.git/kernel/rcu, branch linux-4.18.y Linux kernel stable tree rcutorture: Use monotonic timestamp for stall detection 2018-09-26T06:39:41+00:00 Arnd Bergmann arnd@arndb.de 2018-06-18T14:47:34+00:00 f40d90dd556713bc2247b1b4d8362c04cdf4428a [ Upstream commit 622be33fcbc93e9b672b99ed338369eb5e843ac3 ] The get_seconds() call is deprecated because it overflows on 32-bit architectures. The algorithm in rcu_torture_stall() can deal with the overflow, but another problem here is that using a CLOCK_REALTIME stamp can lead to a false-positive stall warning when a settimeofday() happens concurrently. Using ktime_get_seconds() instead avoids those issues and will never overflow. The added cast to 'unsigned long' however is necessary to make ULONG_CMP_LT() work correctly. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
[ Upstream commit 622be33fcbc93e9b672b99ed338369eb5e843ac3 ]

The get_seconds() call is deprecated because it overflows on 32-bit
architectures. The algorithm in rcu_torture_stall() can deal with
the overflow, but another problem here is that using a CLOCK_REALTIME
stamp can lead to a false-positive stall warning when a settimeofday()
happens concurrently.

Using ktime_get_seconds() instead avoids those issues and will never
overflow. The added cast to 'unsigned long' however is necessary to
make ULONG_CMP_LT() work correctly.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
rcu: Make expedited GPs handle CPU 0 being offline 2018-09-09T08:32:27+00:00 Boqun Feng boqun.feng@gmail.com 2018-06-15T19:06:31+00:00 832fa8183637a5a9e4f595a6eb0125220021fdf5 commit fcc63543650150629c8a873cbef3578770acecd9 upstream. Currently, the parallelized initialization of expedited grace periods uses the workqueue associated with each rcu_node structure's ->grplo field. This works fine unless that CPU is offline. This commit therefore uses the CPU corresponding to the lowest-numbered online CPU, or just queues the work on WORK_CPU_UNBOUND if there are no online CPUs corresponding to this rcu_node structure. Note that this patch uses cpu_is_offline() instead of the usual approach of checking bits in the rcu_node structure's ->qsmaskinitnext field. This is safe because preemption is disabled across both the cpu_is_offline() check and the call to queue_work_on(). Signed-off-by: Boqun Feng <boqun.feng@gmail.com> [ paulmck: Disable preemption to close offline race window. ] Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Apply Peter Zijlstra feedback on CPU selection. ] Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit fcc63543650150629c8a873cbef3578770acecd9 upstream.

Currently, the parallelized initialization of expedited grace periods uses
the workqueue associated with each rcu_node structure's ->grplo field.
This works fine unless that CPU is offline.  This commit therefore uses
the CPU corresponding to the lowest-numbered online CPU, or just queues
the work on WORK_CPU_UNBOUND if there are no online CPUs corresponding
to this rcu_node structure.

Note that this patch uses cpu_is_offline() instead of the usual approach
of checking bits in the rcu_node structure's ->qsmaskinitnext field.  This
is safe because preemption is disabled across both the cpu_is_offline()
check and the call to queue_work_on().

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
[ paulmck: Disable preemption to close offline race window. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Apply Peter Zijlstra feedback on CPU selection. ]
Tested-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
treewide: Use array_size() in vmalloc() 2018-06-12T23:19:22+00:00 Kees Cook keescook@chromium.org 2018-06-12T21:27:11+00:00 42bc47b35320e0e587a88e437e18f80f9c5bcbb2 The vmalloc() function has no 2-factor argument form, so multiplication factors need to be wrapped in array_size(). This patch replaces cases of: vmalloc(a * b) with: vmalloc(array_size(a, b)) as well as handling cases of: vmalloc(a * b * c) with: vmalloc(array3_size(a, b, c)) This does, however, attempt to ignore constant size factors like: vmalloc(4 * 1024) though any constants defined via macros get caught up in the conversion. Any factors with a sizeof() of "unsigned char", "char", and "u8" were dropped, since they're redundant. The Coccinelle script used for this was: // Fix redundant parens around sizeof(). @@ type TYPE; expression THING, E; @@ ( vmalloc( - (sizeof(TYPE)) * E + sizeof(TYPE) * E , ...) | vmalloc( - (sizeof(THING)) * E + sizeof(THING) * E , ...) ) // Drop single-byte sizes and redundant parens. @@ expression COUNT; typedef u8; typedef __u8; @@ ( vmalloc( - sizeof(u8) * (COUNT) + COUNT , ...) | vmalloc( - sizeof(__u8) * (COUNT) + COUNT , ...) | vmalloc( - sizeof(char) * (COUNT) + COUNT , ...) | vmalloc( - sizeof(unsigned char) * (COUNT) + COUNT , ...) | vmalloc( - sizeof(u8) * COUNT + COUNT , ...) | vmalloc( - sizeof(__u8) * COUNT + COUNT , ...) | vmalloc( - sizeof(char) * COUNT + COUNT , ...) | vmalloc( - sizeof(unsigned char) * COUNT + COUNT , ...) ) // 2-factor product with sizeof(type/expression) and identifier or constant. @@ type TYPE; expression THING; identifier COUNT_ID; constant COUNT_CONST; @@ ( vmalloc( - sizeof(TYPE) * (COUNT_ID) + array_size(COUNT_ID, sizeof(TYPE)) , ...) | vmalloc( - sizeof(TYPE) * COUNT_ID + array_size(COUNT_ID, sizeof(TYPE)) , ...) | vmalloc( - sizeof(TYPE) * (COUNT_CONST) + array_size(COUNT_CONST, sizeof(TYPE)) , ...) | vmalloc( - sizeof(TYPE) * COUNT_CONST + array_size(COUNT_CONST, sizeof(TYPE)) , ...) | vmalloc( - sizeof(THING) * (COUNT_ID) + array_size(COUNT_ID, sizeof(THING)) , ...) | vmalloc( - sizeof(THING) * COUNT_ID + array_size(COUNT_ID, sizeof(THING)) , ...) | vmalloc( - sizeof(THING) * (COUNT_CONST) + array_size(COUNT_CONST, sizeof(THING)) , ...) | vmalloc( - sizeof(THING) * COUNT_CONST + array_size(COUNT_CONST, sizeof(THING)) , ...) ) // 2-factor product, only identifiers. @@ identifier SIZE, COUNT; @@ vmalloc( - SIZE * COUNT + array_size(COUNT, SIZE) , ...) // 3-factor product with 1 sizeof(type) or sizeof(expression), with // redundant parens removed. @@ expression THING; identifier STRIDE, COUNT; type TYPE; @@ ( vmalloc( - sizeof(TYPE) * (COUNT) * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | vmalloc( - sizeof(TYPE) * (COUNT) * STRIDE + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | vmalloc( - sizeof(TYPE) * COUNT * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | vmalloc( - sizeof(TYPE) * COUNT * STRIDE + array3_size(COUNT, STRIDE, sizeof(TYPE)) , ...) | vmalloc( - sizeof(THING) * (COUNT) * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | vmalloc( - sizeof(THING) * (COUNT) * STRIDE + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | vmalloc( - sizeof(THING) * COUNT * (STRIDE) + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) | vmalloc( - sizeof(THING) * COUNT * STRIDE + array3_size(COUNT, STRIDE, sizeof(THING)) , ...) ) // 3-factor product with 2 sizeof(variable), with redundant parens removed. @@ expression THING1, THING2; identifier COUNT; type TYPE1, TYPE2; @@ ( vmalloc( - sizeof(TYPE1) * sizeof(TYPE2) * COUNT + array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2)) , ...) | vmalloc( - sizeof(TYPE1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2)) , ...) | vmalloc( - sizeof(THING1) * sizeof(THING2) * COUNT + array3_size(COUNT, sizeof(THING1), sizeof(THING2)) , ...) | vmalloc( - sizeof(THING1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(THING1), sizeof(THING2)) , ...) | vmalloc( - sizeof(TYPE1) * sizeof(THING2) * COUNT + array3_size(COUNT, sizeof(TYPE1), sizeof(THING2)) , ...) | vmalloc( - sizeof(TYPE1) * sizeof(THING2) * (COUNT) + array3_size(COUNT, sizeof(TYPE1), sizeof(THING2)) , ...) ) // 3-factor product, only identifiers, with redundant parens removed. @@ identifier STRIDE, SIZE, COUNT; @@ ( vmalloc( - (COUNT) * STRIDE * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | vmalloc( - COUNT * (STRIDE) * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | vmalloc( - COUNT * STRIDE * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | vmalloc( - (COUNT) * (STRIDE) * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) | vmalloc( - COUNT * (STRIDE) * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | vmalloc( - (COUNT) * STRIDE * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | vmalloc( - (COUNT) * (STRIDE) * (SIZE) + array3_size(COUNT, STRIDE, SIZE) , ...) | vmalloc( - COUNT * STRIDE * SIZE + array3_size(COUNT, STRIDE, SIZE) , ...) ) // Any remaining multi-factor products, first at least 3-factor products // when they're not all constants... @@ expression E1, E2, E3; constant C1, C2, C3; @@ ( vmalloc(C1 * C2 * C3, ...) | vmalloc( - E1 * E2 * E3 + array3_size(E1, E2, E3) , ...) ) // And then all remaining 2 factors products when they're not all constants. @@ expression E1, E2; constant C1, C2; @@ ( vmalloc(C1 * C2, ...) | vmalloc( - E1 * E2 + array_size(E1, E2) , ...) ) Signed-off-by: Kees Cook <keescook@chromium.org> 
The vmalloc() function has no 2-factor argument form, so multiplication
factors need to be wrapped in array_size(). This patch replaces cases of:

        vmalloc(a * b)

with:
        vmalloc(array_size(a, b))

as well as handling cases of:

        vmalloc(a * b * c)

with:

        vmalloc(array3_size(a, b, c))

This does, however, attempt to ignore constant size factors like:

        vmalloc(4 * 1024)

though any constants defined via macros get caught up in the conversion.

Any factors with a sizeof() of "unsigned char", "char", and "u8" were
dropped, since they're redundant.

The Coccinelle script used for this was:

// Fix redundant parens around sizeof().
@@
type TYPE;
expression THING, E;
@@

(
  vmalloc(
-	(sizeof(TYPE)) * E
+	sizeof(TYPE) * E
  , ...)
|
  vmalloc(
-	(sizeof(THING)) * E
+	sizeof(THING) * E
  , ...)
)

// Drop single-byte sizes and redundant parens.
@@
expression COUNT;
typedef u8;
typedef __u8;
@@

(
  vmalloc(
-	sizeof(u8) * (COUNT)
+	COUNT
  , ...)
|
  vmalloc(
-	sizeof(__u8) * (COUNT)
+	COUNT
  , ...)
|
  vmalloc(
-	sizeof(char) * (COUNT)
+	COUNT
  , ...)
|
  vmalloc(
-	sizeof(unsigned char) * (COUNT)
+	COUNT
  , ...)
|
  vmalloc(
-	sizeof(u8) * COUNT
+	COUNT
  , ...)
|
  vmalloc(
-	sizeof(__u8) * COUNT
+	COUNT
  , ...)
|
  vmalloc(
-	sizeof(char) * COUNT
+	COUNT
  , ...)
|
  vmalloc(
-	sizeof(unsigned char) * COUNT
+	COUNT
  , ...)
)

// 2-factor product with sizeof(type/expression) and identifier or constant.
@@
type TYPE;
expression THING;
identifier COUNT_ID;
constant COUNT_CONST;
@@

(
  vmalloc(
-	sizeof(TYPE) * (COUNT_ID)
+	array_size(COUNT_ID, sizeof(TYPE))
  , ...)
|
  vmalloc(
-	sizeof(TYPE) * COUNT_ID
+	array_size(COUNT_ID, sizeof(TYPE))
  , ...)
|
  vmalloc(
-	sizeof(TYPE) * (COUNT_CONST)
+	array_size(COUNT_CONST, sizeof(TYPE))
  , ...)
|
  vmalloc(
-	sizeof(TYPE) * COUNT_CONST
+	array_size(COUNT_CONST, sizeof(TYPE))
  , ...)
|
  vmalloc(
-	sizeof(THING) * (COUNT_ID)
+	array_size(COUNT_ID, sizeof(THING))
  , ...)
|
  vmalloc(
-	sizeof(THING) * COUNT_ID
+	array_size(COUNT_ID, sizeof(THING))
  , ...)
|
  vmalloc(
-	sizeof(THING) * (COUNT_CONST)
+	array_size(COUNT_CONST, sizeof(THING))
  , ...)
|
  vmalloc(
-	sizeof(THING) * COUNT_CONST
+	array_size(COUNT_CONST, sizeof(THING))
  , ...)
)

// 2-factor product, only identifiers.
@@
identifier SIZE, COUNT;
@@

  vmalloc(
-	SIZE * COUNT
+	array_size(COUNT, SIZE)
  , ...)

// 3-factor product with 1 sizeof(type) or sizeof(expression), with
// redundant parens removed.
@@
expression THING;
identifier STRIDE, COUNT;
type TYPE;
@@

(
  vmalloc(
-	sizeof(TYPE) * (COUNT) * (STRIDE)
+	array3_size(COUNT, STRIDE, sizeof(TYPE))
  , ...)
|
  vmalloc(
-	sizeof(TYPE) * (COUNT) * STRIDE
+	array3_size(COUNT, STRIDE, sizeof(TYPE))
  , ...)
|
  vmalloc(
-	sizeof(TYPE) * COUNT * (STRIDE)
+	array3_size(COUNT, STRIDE, sizeof(TYPE))
  , ...)
|
  vmalloc(
-	sizeof(TYPE) * COUNT * STRIDE
+	array3_size(COUNT, STRIDE, sizeof(TYPE))
  , ...)
|
  vmalloc(
-	sizeof(THING) * (COUNT) * (STRIDE)
+	array3_size(COUNT, STRIDE, sizeof(THING))
  , ...)
|
  vmalloc(
-	sizeof(THING) * (COUNT) * STRIDE
+	array3_size(COUNT, STRIDE, sizeof(THING))
  , ...)
|
  vmalloc(
-	sizeof(THING) * COUNT * (STRIDE)
+	array3_size(COUNT, STRIDE, sizeof(THING))
  , ...)
|
  vmalloc(
-	sizeof(THING) * COUNT * STRIDE
+	array3_size(COUNT, STRIDE, sizeof(THING))
  , ...)
)

// 3-factor product with 2 sizeof(variable), with redundant parens removed.
@@
expression THING1, THING2;
identifier COUNT;
type TYPE1, TYPE2;
@@

(
  vmalloc(
-	sizeof(TYPE1) * sizeof(TYPE2) * COUNT
+	array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2))
  , ...)
|
  vmalloc(
-	sizeof(TYPE1) * sizeof(THING2) * (COUNT)
+	array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2))
  , ...)
|
  vmalloc(
-	sizeof(THING1) * sizeof(THING2) * COUNT
+	array3_size(COUNT, sizeof(THING1), sizeof(THING2))
  , ...)
|
  vmalloc(
-	sizeof(THING1) * sizeof(THING2) * (COUNT)
+	array3_size(COUNT, sizeof(THING1), sizeof(THING2))
  , ...)
|
  vmalloc(
-	sizeof(TYPE1) * sizeof(THING2) * COUNT
+	array3_size(COUNT, sizeof(TYPE1), sizeof(THING2))
  , ...)
|
  vmalloc(
-	sizeof(TYPE1) * sizeof(THING2) * (COUNT)
+	array3_size(COUNT, sizeof(TYPE1), sizeof(THING2))
  , ...)
)

// 3-factor product, only identifiers, with redundant parens removed.
@@
identifier STRIDE, SIZE, COUNT;
@@

(
  vmalloc(
-	(COUNT) * STRIDE * SIZE
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
|
  vmalloc(
-	COUNT * (STRIDE) * SIZE
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
|
  vmalloc(
-	COUNT * STRIDE * (SIZE)
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
|
  vmalloc(
-	(COUNT) * (STRIDE) * SIZE
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
|
  vmalloc(
-	COUNT * (STRIDE) * (SIZE)
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
|
  vmalloc(
-	(COUNT) * STRIDE * (SIZE)
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
|
  vmalloc(
-	(COUNT) * (STRIDE) * (SIZE)
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
|
  vmalloc(
-	COUNT * STRIDE * SIZE
+	array3_size(COUNT, STRIDE, SIZE)
  , ...)
)

// Any remaining multi-factor products, first at least 3-factor products
// when they're not all constants...
@@
expression E1, E2, E3;
constant C1, C2, C3;
@@

(
  vmalloc(C1 * C2 * C3, ...)
|
  vmalloc(
-	E1 * E2 * E3
+	array3_size(E1, E2, E3)
  , ...)
)

// And then all remaining 2 factors products when they're not all constants.
@@
expression E1, E2;
constant C1, C2;
@@

(
  vmalloc(C1 * C2, ...)
|
  vmalloc(
-	E1 * E2
+	array_size(E1, E2)
  , ...)
)

Signed-off-by: Kees Cook <keescook@chromium.org>
rcu/x86: Provide early rcu_cpu_starting() callback 2018-05-22T23:12:26+00:00 Peter Zijlstra peterz@infradead.org 2018-05-22T16:50:53+00:00 f64c6013a2029316ea552f99823d116ee5f5f955 The x86/mtrr code does horrific things because hardware. It uses stop_machine_from_inactive_cpu(), which does a wakeup (of the stopper thread on another CPU), which uses RCU, all before the CPU is onlined. RCU complains about this, because wakeups use RCU and RCU does (rightfully) not consider offline CPUs for grace-periods. Fix this by initializing RCU way early in the MTRR case. Tested-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Add !SMP support, per 0day Test Robot report. ] 
The x86/mtrr code does horrific things because hardware. It uses
stop_machine_from_inactive_cpu(), which does a wakeup (of the stopper
thread on another CPU), which uses RCU, all before the CPU is onlined.

RCU complains about this, because wakeups use RCU and RCU does
(rightfully) not consider offline CPUs for grace-periods.

Fix this by initializing RCU way early in the MTRR case.

Tested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Add !SMP support, per 0day Test Robot report. ]
Merge branches 'exp.2018.05.15a', 'fixes.2018.05.15a', 'lock.2018.05.15a' and 'torture.2018.05.15a' into HEAD 2018-05-15T17:33:05+00:00 Paul E. McKenney paulmck@linux.vnet.ibm.com 2018-05-15T17:33:05+00:00 22df7316ac71dc1ac57415349938737d2a229c59 exp.2018.05.15a: Parallelize expedited grace-period initialization. fixes.2018.05.15a: Miscellaneous fixes. lock.2018.05.15a: Decrease lock contention on root rcu_node structure, which is a step towards merging RCU flavors. torture.2018.05.15a: Torture-test updates. 
exp.2018.05.15a: Parallelize expedited grace-period initialization.
fixes.2018.05.15a: Miscellaneous fixes.
lock.2018.05.15a: Decrease lock contention on root rcu_node structure,
	which is a step towards merging RCU flavors.
torture.2018.05.15a: Torture-test updates.
rcutorture: Print end-of-test state 2018-05-15T17:32:08+00:00 Paul E. McKenney paulmck@linux.vnet.ibm.com 2018-04-19T15:43:11+00:00 034777d7f5c6bc5326184ffa63b7a840ef0e9759 This commit adds end-of-test state printout to help check whether RCU shut down nicely. Note that this printout only helps for flavors of RCU that are not used much by the kernel. In particular, for normal RCU having a grace period in progress is expected behavior. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Nicholas Piggin <npiggin@gmail.com> 
This commit adds end-of-test state printout to help check whether RCU
shut down nicely.  Note that this printout only helps for flavors of
RCU that are not used much by the kernel.  In particular, for normal
RCU having a grace period in progress is expected behavior.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
rcu: Drop early GP request check from rcu_gp_kthread() 2018-05-15T17:31:04+00:00 Paul E. McKenney paulmck@linux.vnet.ibm.com 2018-04-19T22:59:55+00:00 a458360af63a36424c9f607015f0858aacb84a19 Now that grace-period requests use funnel locking and now that they set ->gp_flags to RCU_GP_FLAG_INIT even when the RCU grace-period kthread has not yet started, rcu_gp_kthread() no longer needs to check need_any_future_gp() at startup time. This commit therefore removes this check. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Nicholas Piggin <npiggin@gmail.com> 
Now that grace-period requests use funnel locking and now that they
set ->gp_flags to RCU_GP_FLAG_INIT even when the RCU grace-period
kthread has not yet started, rcu_gp_kthread() no longer needs to check
need_any_future_gp() at startup time.  This commit therefore removes
this check.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
rcu: Simplify and inline cpu_needs_another_gp() 2018-05-15T17:30:59+00:00 Paul E. McKenney paulmck@linux.vnet.ibm.com 2018-04-12T23:29:13+00:00 c1935209df8c903fc3a33143223338826fa54bd1 Now that RCU no longer relies on failsafe checks, cpu_needs_another_gp() can be greatly simplified. This simplification eliminates the last call to rcu_future_needs_gp() and to rcu_segcblist_future_gp_needed(), both of which which can then be eliminated. And then, because cpu_needs_another_gp() is called only from __rcu_pending(), it can be inlined and eliminated. This commit carries out the simplification, inlining, and elimination called out above. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Nicholas Piggin <npiggin@gmail.com> 
Now that RCU no longer relies on failsafe checks, cpu_needs_another_gp()
can be greatly simplified.  This simplification eliminates the last
call to rcu_future_needs_gp() and to rcu_segcblist_future_gp_needed(),
both of which which can then be eliminated.  And then, because
cpu_needs_another_gp() is called only from __rcu_pending(), it can be
inlined and eliminated.

This commit carries out the simplification, inlining, and elimination
called out above.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
rcu: The rcu_gp_cleanup() function does not need cpu_needs_another_gp() 2018-05-15T17:30:54+00:00 Paul E. McKenney paulmck@linux.vnet.ibm.com 2018-04-12T23:16:45+00:00 384f77f4cb765707216ea43f9122580d8a07be7d All of the cpu_needs_another_gp() function's checks (except for newly arrived callbacks) have been subsumed into the rcu_gp_cleanup() function's scan of the rcu_node tree. This commit therefore drops the call to cpu_needs_another_gp(). The check for newly arrived callbacks is supplied by rcu_accelerate_cbs(). Any needed advancing (as in the earlier rcu_advance_cbs() call) will be supplied when the corresponding CPU becomes aware of the end of the now-completed grace period. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Nicholas Piggin <npiggin@gmail.com> 
All of the cpu_needs_another_gp() function's checks (except for
newly arrived callbacks) have been subsumed into the rcu_gp_cleanup()
function's scan of the rcu_node tree.  This commit therefore drops the
call to cpu_needs_another_gp().  The check for newly arrived callbacks
is supplied by rcu_accelerate_cbs().  Any needed advancing (as in the
earlier rcu_advance_cbs() call) will be supplied when the corresponding
CPU becomes aware of the end of the now-completed grace period.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>
rcu: Make rcu_start_this_gp() check for out-of-range requests 2018-05-15T17:30:48+00:00 Paul E. McKenney paulmck@linux.vnet.ibm.com 2018-04-19T19:23:34+00:00 665f08f1ce9cf608a9435e11d66f55be4e72540a If rcu_start_this_gp() is invoked with a requested grace period more than three in the future, then either the ->need_future_gp[] array needs to be bigger or the caller needs to be repaired. This commit therefore adds a WARN_ON_ONCE() checking for this condition. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Nicholas Piggin <npiggin@gmail.com> 
If rcu_start_this_gp() is invoked with a requested grace period more
than three in the future, then either the ->need_future_gp[] array
needs to be bigger or the caller needs to be repaired.  This commit
therefore adds a WARN_ON_ONCE() checking for this condition.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Nicholas Piggin <npiggin@gmail.com>