From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>, Will Deacon <will.deacon@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org, x86@kernel.org,
Davidlohr Bueso <dave@stgolabs.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
huang ying <huang.ying.caritas@gmail.com>
Subject: Re: [PATCH v4 04/16] locking/rwsem: Implement a new locking scheme
Date: Tue, 16 Apr 2019 16:42:31 +0200 [thread overview]
Message-ID: <20190416144231.GQ14281@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190416141820.GO4038@hirez.programming.kicks-ass.net>
On Tue, Apr 16, 2019 at 04:18:20PM +0200, Peter Zijlstra wrote:
> On Tue, Apr 16, 2019 at 09:32:38AM -0400, Waiman Long wrote:
> > On 04/16/2019 09:22 AM, Peter Zijlstra wrote:
> > > On Sat, Apr 13, 2019 at 01:22:47PM -0400, Waiman Long wrote:
> > >> +#define RWSEM_COUNT_LOCKED(c) ((c) & RWSEM_LOCK_MASK)
> > > The above doesn't seem to make it more readable or shorter.
> >
> > Fair enough. I can remove that macro.
>
> I did the same for the HANDOFF patch but seem to have misplaced the
> delta and have already refreshed the patch.
Had to redo it, so here goes:
---
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -102,9 +102,6 @@
#define RWSEM_READ_FAILED_MASK (RWSEM_WRITER_MASK|RWSEM_FLAG_WAITERS|\
RWSEM_FLAG_HANDOFF)
-#define RWSEM_COUNT_HANDOFF(c) ((c) & RWSEM_FLAG_HANDOFF)
-#define RWSEM_COUNT_LOCKED_OR_HANDOFF(c) \
- ((c) & (RWSEM_LOCK_MASK|RWSEM_FLAG_HANDOFF))
/*
* All writes to owner are protected by WRITE_ONCE() to make sure that
* store tearing can't happen as optimistic spinners may read and use
@@ -365,7 +362,7 @@ static void __rwsem_mark_wake(struct rw_
/*
* Clear the handoff flag
*/
- if (woken && RWSEM_COUNT_HANDOFF(atomic_long_read(&sem->count)))
+ if (woken && (atomic_long_read(&sem->count) & RWSEM_FLAG_HANDOFF))
adjustment -= RWSEM_FLAG_HANDOFF;
if (adjustment)
@@ -387,7 +384,7 @@ static inline bool rwsem_try_write_lock(
retry:
if (count & RWSEM_LOCK_MASM)) {
- if (RWSEM_COUNT_HANDOFF(count) || (wstate != WRITER_HANDOFF))
+ if ((count & RWSEM_FLAG_HANDOFF) || (wstate != WRITER_HANDOFF))
return false;
/*
* The lock may become free just before setting handoff bit.
@@ -398,7 +395,7 @@ static inline bool rwsem_try_write_lock(
goto retry;
}
- if ((wstate == WRITER_NOT_FIRST) && RWSEM_COUNT_HANDOFF(count))
+ if ((wstate == WRITER_NOT_FIRST) && (count & RWSEM_FLAG_HANDOFF))
return false;
new = (count & ~RWSEM_FLAG_HANDOFF) + RWSEM_WRITER_LOCKED -
@@ -409,7 +406,7 @@ static inline bool rwsem_try_write_lock(
return true;
}
- if (unlikely((wstate == WRITER_HANDOFF) && !RWSEM_COUNT_HANDOFF(count)))
+ if (unlikely((wstate == WRITER_HANDOFF) && !(count & RWSEM_FLAG_HANDOFF)))
goto retry;
return false;
@@ -704,7 +701,7 @@ __rwsem_down_write_failed_common(struct
rwsem_waiter_is_first(sem, &waiter))
wstate = WRITER_FIRST;
- if (!RWSEM_COUNT_LOCKED(count))
+ if (!(count & RWSEM_LOCK_MASK))
break;
/*
next prev parent reply other threads:[~2019-04-16 14:42 UTC|newest]
Thread overview: 112+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-13 17:22 [PATCH v4 00/16] locking/rwsem: Rwsem rearchitecture part 2 Waiman Long
2019-04-13 17:22 ` [PATCH v4 01/16] locking/rwsem: Prevent unneeded warning during locking selftest Waiman Long
2019-04-18 8:04 ` [tip:locking/core] " tip-bot for Waiman Long
2019-04-13 17:22 ` [PATCH v4 02/16] locking/rwsem: Make owner available even if !CONFIG_RWSEM_SPIN_ON_OWNER Waiman Long
2019-04-13 17:22 ` [PATCH v4 03/16] locking/rwsem: Remove rwsem_wake() wakeup optimization Waiman Long
2019-04-13 17:22 ` [PATCH v4 04/16] locking/rwsem: Implement a new locking scheme Waiman Long
2019-04-16 13:22 ` Peter Zijlstra
2019-04-16 13:32 ` Waiman Long
2019-04-16 14:18 ` Peter Zijlstra
2019-04-16 14:42 ` Peter Zijlstra [this message]
2019-04-13 17:22 ` [PATCH v4 05/16] locking/rwsem: Merge rwsem.h and rwsem-xadd.c into rwsem.c Waiman Long
2019-04-13 17:22 ` [PATCH v4 06/16] locking/rwsem: Code cleanup after files merging Waiman Long
2019-04-16 16:01 ` Peter Zijlstra
2019-04-16 16:17 ` Peter Zijlstra
2019-04-16 19:45 ` Waiman Long
2019-04-13 17:22 ` [PATCH v4 07/16] locking/rwsem: Implement lock handoff to prevent lock starvation Waiman Long
2019-04-16 14:12 ` Peter Zijlstra
2019-04-16 20:26 ` Waiman Long
2019-04-16 21:07 ` Waiman Long
2019-04-17 7:13 ` Peter Zijlstra
2019-04-17 16:22 ` Waiman Long
2019-04-16 15:49 ` Peter Zijlstra
2019-04-16 16:15 ` Peter Zijlstra
2019-04-16 18:41 ` Waiman Long
2019-04-16 18:16 ` Waiman Long
2019-04-16 18:32 ` Peter Zijlstra
2019-04-17 7:35 ` Peter Zijlstra
2019-04-17 16:35 ` Waiman Long
2019-04-17 8:05 ` Peter Zijlstra
2019-04-17 16:39 ` Waiman Long
2019-04-18 8:22 ` Peter Zijlstra
2019-04-17 8:17 ` Peter Zijlstra
2019-04-13 17:22 ` [PATCH v4 08/16] locking/rwsem: Make rwsem_spin_on_owner() return owner state Waiman Long
2019-04-17 9:00 ` Peter Zijlstra
2019-04-17 16:42 ` Waiman Long
2019-04-17 10:19 ` Peter Zijlstra
2019-04-17 16:53 ` Waiman Long
2019-04-17 12:41 ` Peter Zijlstra
2019-04-17 12:47 ` Peter Zijlstra
2019-04-17 18:29 ` Waiman Long
2019-04-18 8:39 ` Peter Zijlstra
2019-04-17 13:00 ` Peter Zijlstra
2019-04-17 18:50 ` Waiman Long
2019-04-13 17:22 ` [PATCH v4 09/16] locking/rwsem: Ensure an RT task will not spin on reader Waiman Long
2019-04-17 13:18 ` Peter Zijlstra
2019-04-17 18:47 ` Waiman Long
2019-04-18 8:52 ` Peter Zijlstra
2019-04-18 13:27 ` Waiman Long
2019-04-13 17:22 ` [PATCH v4 10/16] locking/rwsem: Wake up almost all readers in wait queue Waiman Long
2019-04-16 16:50 ` Davidlohr Bueso
2019-04-16 17:37 ` Waiman Long
2019-04-17 13:39 ` Peter Zijlstra
2019-04-17 17:16 ` Waiman Long
2019-04-13 17:22 ` [PATCH v4 11/16] locking/rwsem: Enable readers spinning on writer Waiman Long
2019-04-17 13:56 ` Peter Zijlstra
2019-04-17 17:34 ` Waiman Long
2019-04-18 8:57 ` Peter Zijlstra
2019-04-18 14:35 ` Waiman Long
2019-04-17 13:58 ` Peter Zijlstra
2019-04-17 17:45 ` Waiman Long
2019-04-18 9:00 ` Peter Zijlstra
2019-04-18 13:40 ` Waiman Long
2019-04-17 14:05 ` Peter Zijlstra
2019-04-17 17:51 ` Waiman Long
2019-04-18 9:11 ` Peter Zijlstra
2019-04-18 14:37 ` Waiman Long
2019-04-13 17:22 ` [PATCH v4 12/16] locking/rwsem: Enable time-based spinning on reader-owned rwsem Waiman Long
2019-04-18 13:06 ` Peter Zijlstra
2019-04-18 15:15 ` Waiman Long
2019-04-19 7:56 ` Peter Zijlstra
2019-04-19 14:33 ` Waiman Long
2019-04-19 15:36 ` Waiman Long
2019-04-13 17:22 ` [PATCH v4 13/16] locking/rwsem: Add more rwsem owner access helpers Waiman Long
2019-04-13 17:22 ` [PATCH v4 14/16] locking/rwsem: Guard against making count negative Waiman Long
2019-04-18 13:51 ` Peter Zijlstra
2019-04-18 14:08 ` Waiman Long
2019-04-18 14:30 ` Peter Zijlstra
2019-04-18 14:40 ` Peter Zijlstra
2019-04-18 14:54 ` Waiman Long
2019-04-19 10:26 ` Peter Zijlstra
2019-04-19 12:02 ` Peter Zijlstra
2019-04-19 13:03 ` Peter Zijlstra
2019-04-19 13:15 ` Peter Zijlstra
2019-04-19 19:39 ` Waiman Long
2019-04-21 21:07 ` Waiman Long
2019-04-23 14:17 ` Peter Zijlstra
2019-04-23 14:31 ` Waiman Long
2019-04-23 16:27 ` Linus Torvalds
2019-04-23 19:12 ` Waiman Long
2019-04-23 19:34 ` Peter Zijlstra
2019-04-23 19:41 ` Waiman Long
2019-04-23 19:55 ` [PATCH] bpf: Fix preempt_enable_no_resched() abuse Peter Zijlstra
2019-04-23 20:03 ` [PATCH] trace: " Peter Zijlstra
2019-04-23 23:58 ` Steven Rostedt
2019-04-29 6:39 ` [tip:sched/core] " tip-bot for Peter Zijlstra
2019-04-29 13:31 ` Steven Rostedt
2019-04-29 14:08 ` Ingo Molnar
2019-04-23 20:27 ` [PATCH] bpf: " Linus Torvalds
2019-04-23 20:35 ` Peter Zijlstra
2019-04-23 20:45 ` Linus Torvalds
2019-04-24 13:19 ` Peter Zijlstra
2019-04-25 21:23 ` Alexei Starovoitov
2019-04-26 7:14 ` Peter Zijlstra
2019-04-24 7:09 ` [PATCH v4 14/16] locking/rwsem: Guard against making count negative Peter Zijlstra
2019-04-24 16:49 ` Waiman Long
2019-04-24 17:01 ` Peter Zijlstra
2019-04-24 17:10 ` Waiman Long
2019-04-24 17:56 ` Linus Torvalds
2019-04-13 17:22 ` [PATCH v4 15/16] locking/rwsem: Merge owner into count on x86-64 Waiman Long
2019-04-18 14:28 ` Peter Zijlstra
2019-04-18 14:40 ` Waiman Long
2019-04-13 17:22 ` [PATCH v4 16/16] locking/rwsem: Remove redundant computation of writer lock word Waiman Long
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