[rcu:from-joel.2019.08.16a 143/172] kernel/rcu/tree.c:2808:6: note: in expansion of macro 'xchg'

From: kbuild test robot
Date: Fri Aug 16 2019 - 17:11:13 EST

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tree: https://kernel.googlesource.com/pub/scm/linux/kernel/git/paulmck/linux-rcu.git from-joel.2019.08.16a
head: 01b0e4d3e0ac279b295bc06a3591f0b810b9908f
commit: bda80ba9decc7a32413e88d2f070de180c4b76ab [143/172] rcu/tree: Add basic support for kfree_rcu() batching
config: riscv-defconfig (attached as .config)
compiler: riscv64-linux-gcc (GCC) 7.4.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
git checkout bda80ba9decc7a32413e88d2f070de180c4b76ab
# save the attached .config to linux build tree
GCC_VERSION=7.4.0 make.cross ARCH=riscv

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@xxxxxxxxx>

All error/warnings (new ones prefixed by >>):

In file included from arch/riscv/include/asm/atomic.h:19:0,
from include/linux/atomic.h:7,
from include/linux/spinlock.h:445,
from kernel/rcu/tree.c:23:
kernel/rcu/tree.c: In function 'kfree_rcu_monitor':
>> arch/riscv/include/asm/cmpxchg.h:140:2: warning: '__ret' is used uninitialized in this function [-Wuninitialized]
__ret; \
^~~~~
arch/riscv/include/asm/cmpxchg.h:121:21: note: '__ret' was declared here
__typeof__(*(ptr)) __ret; \
^
>> arch/riscv/include/asm/cmpxchg.h:146:23: note: in expansion of macro '__xchg'
(__typeof__(*(ptr))) __xchg((ptr), _x_, sizeof(*(ptr))); \
^~~~~~
>> kernel/rcu/tree.c:2808:6: note: in expansion of macro 'xchg'
if (xchg(&krcp->monitor_todo, false))
^~~~
In file included from include/linux/kernel.h:11:0,
from kernel/rcu/tree.c:21:
>> include/linux/compiler.h:350:38: error: call to '__compiletime_assert_2808' declared with attribute error: BUILD_BUG failed
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^
include/linux/compiler.h:331:4: note: in definition of macro '__compiletime_assert'
prefix ## suffix(); \
^~~~~~
include/linux/compiler.h:350:2: note: in expansion of macro '_compiletime_assert'
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^~~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
^~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
^~~~~~~~~~~~~~~~
>> arch/riscv/include/asm/cmpxchg.h:138:3: note: in expansion of macro 'BUILD_BUG'
BUILD_BUG(); \
^~~~~~~~~
>> arch/riscv/include/asm/cmpxchg.h:146:23: note: in expansion of macro '__xchg'
(__typeof__(*(ptr))) __xchg((ptr), _x_, sizeof(*(ptr))); \
^~~~~~
>> kernel/rcu/tree.c:2808:6: note: in expansion of macro 'xchg'
if (xchg(&krcp->monitor_todo, false))
^~~~
In function 'kfree_rcu_drain_unlock',
inlined from 'kfree_rcu_monitor' at kernel/rcu/tree.c:2809:3:
include/linux/compiler.h:350:38: error: call to '__compiletime_assert_2792' declared with attribute error: BUILD_BUG failed
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^
include/linux/compiler.h:331:4: note: in definition of macro '__compiletime_assert'
prefix ## suffix(); \
^~~~~~
include/linux/compiler.h:350:2: note: in expansion of macro '_compiletime_assert'
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^~~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
^~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
^~~~~~~~~~~~~~~~
>> arch/riscv/include/asm/cmpxchg.h:138:3: note: in expansion of macro 'BUILD_BUG'
BUILD_BUG(); \
^~~~~~~~~
>> arch/riscv/include/asm/cmpxchg.h:146:23: note: in expansion of macro '__xchg'
(__typeof__(*(ptr))) __xchg((ptr), _x_, sizeof(*(ptr))); \
^~~~~~
kernel/rcu/tree.c:2792:7: note: in expansion of macro 'xchg'
if (!xchg(&krcp->monitor_todo, true))
^~~~
kernel/rcu/tree.c: In function 'kfree_call_rcu':
>> kernel/rcu/tree.c:2860:5: warning: '__ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
if (!xchg(&krcp->monitor_todo, true))
^
In file included from include/linux/kernel.h:11:0,
from kernel/rcu/tree.c:21:
include/linux/compiler.h:350:38: error: call to '__compiletime_assert_2860' declared with attribute error: BUILD_BUG failed
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^
include/linux/compiler.h:331:4: note: in definition of macro '__compiletime_assert'
prefix ## suffix(); \
^~~~~~
include/linux/compiler.h:350:2: note: in expansion of macro '_compiletime_assert'
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^~~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
^~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
^~~~~~~~~~~~~~~~
>> arch/riscv/include/asm/cmpxchg.h:138:3: note: in expansion of macro 'BUILD_BUG'
BUILD_BUG(); \
^~~~~~~~~
>> arch/riscv/include/asm/cmpxchg.h:146:23: note: in expansion of macro '__xchg'
(__typeof__(*(ptr))) __xchg((ptr), _x_, sizeof(*(ptr))); \
^~~~~~
kernel/rcu/tree.c:2860:7: note: in expansion of macro 'xchg'
if (!xchg(&krcp->monitor_todo, true))
^~~~
--
In file included from arch/riscv/include/asm/atomic.h:19:0,
from include/linux/atomic.h:7,
from include/linux/spinlock.h:445,
from kernel//rcu/tree.c:23:
kernel//rcu/tree.c: In function 'kfree_rcu_monitor':
>> arch/riscv/include/asm/cmpxchg.h:140:2: warning: '__ret' is used uninitialized in this function [-Wuninitialized]
__ret; \
^~~~~
arch/riscv/include/asm/cmpxchg.h:121:21: note: '__ret' was declared here
__typeof__(*(ptr)) __ret; \
^
>> arch/riscv/include/asm/cmpxchg.h:146:23: note: in expansion of macro '__xchg'
(__typeof__(*(ptr))) __xchg((ptr), _x_, sizeof(*(ptr))); \
^~~~~~
kernel//rcu/tree.c:2808:6: note: in expansion of macro 'xchg'
if (xchg(&krcp->monitor_todo, false))
^~~~
In file included from include/linux/kernel.h:11:0,
from kernel//rcu/tree.c:21:
>> include/linux/compiler.h:350:38: error: call to '__compiletime_assert_2808' declared with attribute error: BUILD_BUG failed
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^
include/linux/compiler.h:331:4: note: in definition of macro '__compiletime_assert'
prefix ## suffix(); \
^~~~~~
include/linux/compiler.h:350:2: note: in expansion of macro '_compiletime_assert'
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^~~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
^~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
^~~~~~~~~~~~~~~~
>> arch/riscv/include/asm/cmpxchg.h:138:3: note: in expansion of macro 'BUILD_BUG'
BUILD_BUG(); \
^~~~~~~~~
>> arch/riscv/include/asm/cmpxchg.h:146:23: note: in expansion of macro '__xchg'
(__typeof__(*(ptr))) __xchg((ptr), _x_, sizeof(*(ptr))); \
^~~~~~
kernel//rcu/tree.c:2808:6: note: in expansion of macro 'xchg'
if (xchg(&krcp->monitor_todo, false))
^~~~
In function 'kfree_rcu_drain_unlock',
inlined from 'kfree_rcu_monitor' at kernel//rcu/tree.c:2809:3:
include/linux/compiler.h:350:38: error: call to '__compiletime_assert_2792' declared with attribute error: BUILD_BUG failed
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^
include/linux/compiler.h:331:4: note: in definition of macro '__compiletime_assert'
prefix ## suffix(); \
^~~~~~
include/linux/compiler.h:350:2: note: in expansion of macro '_compiletime_assert'
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^~~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
^~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
^~~~~~~~~~~~~~~~
>> arch/riscv/include/asm/cmpxchg.h:138:3: note: in expansion of macro 'BUILD_BUG'
BUILD_BUG(); \
^~~~~~~~~
>> arch/riscv/include/asm/cmpxchg.h:146:23: note: in expansion of macro '__xchg'
(__typeof__(*(ptr))) __xchg((ptr), _x_, sizeof(*(ptr))); \
^~~~~~
kernel//rcu/tree.c:2792:7: note: in expansion of macro 'xchg'
if (!xchg(&krcp->monitor_todo, true))
^~~~
kernel//rcu/tree.c: In function 'kfree_call_rcu':
kernel//rcu/tree.c:2860:5: warning: '__ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
if (!xchg(&krcp->monitor_todo, true))
^
In file included from include/linux/kernel.h:11:0,
from kernel//rcu/tree.c:21:
include/linux/compiler.h:350:38: error: call to '__compiletime_assert_2860' declared with attribute error: BUILD_BUG failed
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^
include/linux/compiler.h:331:4: note: in definition of macro '__compiletime_assert'
prefix ## suffix(); \
^~~~~~
include/linux/compiler.h:350:2: note: in expansion of macro '_compiletime_assert'
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
^~~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
^~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
^~~~~~~~~~~~~~~~
>> arch/riscv/include/asm/cmpxchg.h:138:3: note: in expansion of macro 'BUILD_BUG'
BUILD_BUG(); \
^~~~~~~~~
>> arch/riscv/include/asm/cmpxchg.h:146:23: note: in expansion of macro '__xchg'
(__typeof__(*(ptr))) __xchg((ptr), _x_, sizeof(*(ptr))); \
^~~~~~
kernel//rcu/tree.c:2860:7: note: in expansion of macro 'xchg'
if (!xchg(&krcp->monitor_todo, true))
^~~~

vim +/xchg +2808 kernel/rcu/tree.c

2776
2777 static inline void kfree_rcu_drain_unlock(struct kfree_rcu_cpu *krcp,
2778 unsigned long flags)
2779 {
2780 /* Flush ->head to ->head_free, all objects on ->head_free will be
2781 * kfree'd after a grace period.
2782 */
2783 if (queue_kfree_rcu_work(krcp)) {
2784 /* Success! Our job is done here. */
2785 spin_unlock_irqrestore(&krcp->lock, flags);
2786 return;
2787 }
2788
2789 /* Previous batch that was queued to RCU did not get free yet, let us
2790 * try again soon.
2791 */
> 2792 if (!xchg(&krcp->monitor_todo, true))
2793 schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
2794 spin_unlock_irqrestore(&krcp->lock, flags);
2795 }
2796
2797 /*
2798 * This function is invoked after the KFREE_DRAIN_JIFFIES timeout has elapsed,
2799 * and it drains the specified kfree_rcu_cpu structure's ->head list.
2800 */
2801 static void kfree_rcu_monitor(struct work_struct *work)
2802 {
2803 unsigned long flags;
2804 struct kfree_rcu_cpu *krcp = container_of(work, struct kfree_rcu_cpu,
2805 monitor_work.work);
2806
2807 spin_lock_irqsave(&krcp->lock, flags);
> 2808 if (xchg(&krcp->monitor_todo, false))
2809 kfree_rcu_drain_unlock(krcp, flags);
2810 else
2811 spin_unlock_irqrestore(&krcp->lock, flags);
2812 }
2813
2814 /*
2815 * This version of kfree_call_rcu does not do batching of kfree_rcu() requests.
2816 * Used only by rcuperf torture test for comparison with kfree_rcu_batch().
2817 */
2818 void kfree_call_rcu_nobatch(struct rcu_head *head, rcu_callback_t func)
2819 {
2820 __call_rcu(head, func, 1);
2821 }
2822 EXPORT_SYMBOL_GPL(kfree_call_rcu_nobatch);
2823
2824 /*
2825 * Queue a request for lazy invocation of kfree() after a grace period.
2826 *
2827 * Each kfree_call_rcu() request is added to a batch. The batch will be drained
2828 * every KFREE_DRAIN_JIFFIES number of jiffies. All the objects in the batch
2829 * will be kfree'd in workqueue context. This allows us to:
2830 *
2831 * 1. Batch requests together to reduce the number of grace periods during
2832 * heavy kfree_rcu() load.
2833 *
2834 * 2. In the future, makes it possible to use kfree_bulk() on a large number of
2835 * kfree_rcu() requests thus reducing the per-object overhead of kfree() and
2836 * also reducing cache misses.
2837 */
2838 void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
2839 {
2840 unsigned long flags;
2841 struct kfree_rcu_cpu *krcp;
2842
2843 /* kfree_call_rcu() batching requires timers to be up. If the scheduler
2844 * is not yet up, just skip batching and do the non-batched version.
2845 */
2846 if (rcu_scheduler_active != RCU_SCHEDULER_RUNNING)
2847 return kfree_call_rcu_nobatch(head, func);
2848
2849 head->func = func;
2850
2851 local_irq_save(flags); /* For safely calling this_cpu_ptr(). */
2852 krcp = this_cpu_ptr(&krc);
2853 spin_lock(&krcp->lock);
2854
2855 /* Queue the kfree but don't yet schedule the batch. */
2856 head->next = krcp->head;
2857 krcp->head = head;
2858
2859 /* Schedule monitor for timely drain after KFREE_DRAIN_JIFFIES. */
> 2860 if (!xchg(&krcp->monitor_todo, true))
2861 schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
2862
2863 spin_unlock(&krcp->lock);
2864 local_irq_restore(flags);
2865 }
2866 EXPORT_SYMBOL_GPL(kfree_call_rcu);
2867

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