Re: [PATCH v2 06/28] locking/rwlocks: Add contention detection for rwlocks
From: Waiman Long
Date: Tue Feb 09 2021 - 21:03:29 EST
On 2/9/21 7:27 PM, Waiman Long wrote:
On 2/9/21 5:25 PM, Guenter Roeck wrote:
On Tue, Feb 09, 2021 at 04:46:02PM -0500, Waiman Long wrote:
On 2/9/21 3:39 PM, Guenter Roeck wrote:
On Tue, Feb 02, 2021 at 10:57:12AM -0800, Ben Gardon wrote:
rwlocks do not currently have any facility to detect contention
like spinlocks do. In order to allow users of rwlocks to better
manage
latency, add contention detection for queued rwlocks.
CC: Ingo Molnar <mingo@xxxxxxxxxx>
CC: Will Deacon <will@xxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Acked-by: Davidlohr Bueso <dbueso@xxxxxxx>
Acked-by: Waiman Long <longman@xxxxxxxxxx>
Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx>
When building mips:defconfig, this patch results in:
Error log:
In file included from include/linux/spinlock.h:90,
from include/linux/ipc.h:5,
from include/uapi/linux/sem.h:5,
from include/linux/sem.h:5,
from include/linux/compat.h:14,
from arch/mips/kernel/asm-offsets.c:12:
arch/mips/include/asm/spinlock.h:17:28: error: redefinition of
'queued_spin_unlock'
17 | #define queued_spin_unlock queued_spin_unlock
| ^~~~~~~~~~~~~~~~~~
arch/mips/include/asm/spinlock.h:22:20: note: in expansion of macro
'queued_spin_unlock'
22 | static inline void queued_spin_unlock(struct qspinlock
*lock)
| ^~~~~~~~~~~~~~~~~~
In file included from include/asm-generic/qrwlock.h:17,
from ./arch/mips/include/generated/asm/qrwlock.h:1,
from arch/mips/include/asm/spinlock.h:13,
from include/linux/spinlock.h:90,
from include/linux/ipc.h:5,
from include/uapi/linux/sem.h:5,
from include/linux/sem.h:5,
from include/linux/compat.h:14,
from arch/mips/kernel/asm-offsets.c:12:
include/asm-generic/qspinlock.h:94:29: note: previous definition of
'queued_spin_unlock' was here
94 | static __always_inline void queued_spin_unlock(struct
qspinlock *lock)
| ^~~~~~~~~~~~~~~~~~
I think the compile error is caused by the improper header file
inclusion
ordering. Can you try the following change to see if it can fix the
compile
error?
That results in:
In file included from ./arch/mips/include/generated/asm/qrwlock.h:1,
from ./arch/mips/include/asm/spinlock.h:13,
from ./include/linux/spinlock.h:90,
from ./include/linux/ipc.h:5,
from ./include/uapi/linux/sem.h:5,
from ./include/linux/sem.h:5,
from ./include/linux/compat.h:14,
from arch/mips/kernel/asm-offsets.c:12:
./include/asm-generic/qrwlock.h: In function
'queued_rwlock_is_contended':
./include/asm-generic/qrwlock.h:127:9: error: implicit declaration of
function 'arch_spin_is_locked'
Guenter
It is because in arch/mips/include/asm/spinlock.h, asm/qrwlock.h is
included before asm/qspinlock.h. The compilation error should be gone
if the asm/qrwlock.h is removed or moved after asm/qspinlock.h.
After thinking a bit more, I think we should remove asm/qrwlock.h in
arch/mips/include/asm/spinlock.h. qrwlock and qspinlocks are
independent. An architecture can include one but not the other. Also
there is no point in including qrwlock.h in a asm/spinlock.h.
Regards,
Longman