From: Guo Ren <guoren@kernel.org> To: Peter Zijlstra <peterz@infradead.org> Cc: Palmer Dabbelt <palmer@rivosinc.com>, Arnd Bergmann <arnd@arndb.de>, Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>, Waiman Long <longman@redhat.com>, Boqun Feng <boqun.feng@gmail.com>, linux-riscv <linux-riscv@lists.infradead.org>, linux-arch <linux-arch@vger.kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Guo Ren <guoren@linux.alibaba.com> Subject: Re: [PATCH V7 1/5] asm-generic: ticket-lock: Remove unnecessary atomic_read Date: Mon, 4 Jul 2022 19:10:17 +0800 [thread overview] Message-ID: <CAJF2gTTJn7facrxSzU+_ZKhVdXxJEYfGWpP7QqArVUTazw_JHg@mail.gmail.com> (raw) In-Reply-To: <YsK4Z9w0tFtgkni8@hirez.programming.kicks-ass.net> On Mon, Jul 4, 2022 at 5:52 PM Peter Zijlstra <peterz@infradead.org> wrote: > > On Tue, Jun 28, 2022 at 04:17:03AM -0400, guoren@kernel.org wrote: > > From: Guo Ren <guoren@linux.alibaba.com> > > > > Remove unnecessary atomic_read in arch_spin_value_unlocked(lock), > > because the value has been in lock. This patch could prevent > > arch_spin_value_unlocked contend spin_lock data again. > > > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com> > > Signed-off-by: Guo Ren <guoren@kernel.org> > > Cc: Peter Zijlstra (Intel) <peterz@infradead.org> > > Cc: Arnd Bergmann <arnd@arndb.de> > > Cc: Palmer Dabbelt <palmer@rivosinc.com> > > --- > > include/asm-generic/spinlock.h | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/include/asm-generic/spinlock.h b/include/asm-generic/spinlock.h > > index fdfebcb050f4..f1e4fa100f5a 100644 > > --- a/include/asm-generic/spinlock.h > > +++ b/include/asm-generic/spinlock.h > > @@ -84,7 +84,9 @@ static __always_inline int arch_spin_is_contended(arch_spinlock_t *lock) > > > > static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock) > > { > > - return !arch_spin_is_locked(&lock); > > + u32 val = lock.counter; > > + > > + return ((val >> 16) == (val & 0xffff)); > > } > > Wouldn't the right thing be to flip arch_spin_is_locked() and > arch_spin_value_is_unlocked() ? Okay, I agree with your patch. Next version, I would take the below code. > > > diff --git a/include/asm-generic/spinlock.h b/include/asm-generic/spinlock.h > index fdfebcb050f4..63ab4da262f2 100644 > --- a/include/asm-generic/spinlock.h > +++ b/include/asm-generic/spinlock.h > @@ -68,23 +68,25 @@ static __always_inline void arch_spin_unlock(arch_spinlock_t *lock) > smp_store_release(ptr, (u16)val + 1); > } > > -static __always_inline int arch_spin_is_locked(arch_spinlock_t *lock) > +static __always_inline int arch_spin_is_contended(arch_spinlock_t *lock) > { > u32 val = atomic_read(lock); > > - return ((val >> 16) != (val & 0xffff)); > + return (s16)((val >> 16) - (val & 0xffff)) > 1; > } > > -static __always_inline int arch_spin_is_contended(arch_spinlock_t *lock) > +static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock) > { > - u32 val = atomic_read(lock); > + u32 val = lock.counter; > > - return (s16)((val >> 16) - (val & 0xffff)) > 1; > + return ((val >> 16) == (val & 0xffff)); > } > > -static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock) > +static __always_inline int arch_spin_is_locked(arch_spinlock_t *lock) > { > - return !arch_spin_is_locked(&lock); > + arch_spinlock_t val = READ_ONCE(*lock); > + > + return !arch_spin_value_unlocked(val); > } > > #include <asm/qrwlock.h> > -- Best Regards Guo Ren ML: https://lore.kernel.org/linux-csky/
WARNING: multiple messages have this Message-ID (diff)
From: Guo Ren <guoren@kernel.org> To: Peter Zijlstra <peterz@infradead.org> Cc: Palmer Dabbelt <palmer@rivosinc.com>, Arnd Bergmann <arnd@arndb.de>, Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>, Waiman Long <longman@redhat.com>, Boqun Feng <boqun.feng@gmail.com>, linux-riscv <linux-riscv@lists.infradead.org>, linux-arch <linux-arch@vger.kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Guo Ren <guoren@linux.alibaba.com> Subject: Re: [PATCH V7 1/5] asm-generic: ticket-lock: Remove unnecessary atomic_read Date: Mon, 4 Jul 2022 19:10:17 +0800 [thread overview] Message-ID: <CAJF2gTTJn7facrxSzU+_ZKhVdXxJEYfGWpP7QqArVUTazw_JHg@mail.gmail.com> (raw) In-Reply-To: <YsK4Z9w0tFtgkni8@hirez.programming.kicks-ass.net> On Mon, Jul 4, 2022 at 5:52 PM Peter Zijlstra <peterz@infradead.org> wrote: > > On Tue, Jun 28, 2022 at 04:17:03AM -0400, guoren@kernel.org wrote: > > From: Guo Ren <guoren@linux.alibaba.com> > > > > Remove unnecessary atomic_read in arch_spin_value_unlocked(lock), > > because the value has been in lock. This patch could prevent > > arch_spin_value_unlocked contend spin_lock data again. > > > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com> > > Signed-off-by: Guo Ren <guoren@kernel.org> > > Cc: Peter Zijlstra (Intel) <peterz@infradead.org> > > Cc: Arnd Bergmann <arnd@arndb.de> > > Cc: Palmer Dabbelt <palmer@rivosinc.com> > > --- > > include/asm-generic/spinlock.h | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/include/asm-generic/spinlock.h b/include/asm-generic/spinlock.h > > index fdfebcb050f4..f1e4fa100f5a 100644 > > --- a/include/asm-generic/spinlock.h > > +++ b/include/asm-generic/spinlock.h > > @@ -84,7 +84,9 @@ static __always_inline int arch_spin_is_contended(arch_spinlock_t *lock) > > > > static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock) > > { > > - return !arch_spin_is_locked(&lock); > > + u32 val = lock.counter; > > + > > + return ((val >> 16) == (val & 0xffff)); > > } > > Wouldn't the right thing be to flip arch_spin_is_locked() and > arch_spin_value_is_unlocked() ? Okay, I agree with your patch. Next version, I would take the below code. > > > diff --git a/include/asm-generic/spinlock.h b/include/asm-generic/spinlock.h > index fdfebcb050f4..63ab4da262f2 100644 > --- a/include/asm-generic/spinlock.h > +++ b/include/asm-generic/spinlock.h > @@ -68,23 +68,25 @@ static __always_inline void arch_spin_unlock(arch_spinlock_t *lock) > smp_store_release(ptr, (u16)val + 1); > } > > -static __always_inline int arch_spin_is_locked(arch_spinlock_t *lock) > +static __always_inline int arch_spin_is_contended(arch_spinlock_t *lock) > { > u32 val = atomic_read(lock); > > - return ((val >> 16) != (val & 0xffff)); > + return (s16)((val >> 16) - (val & 0xffff)) > 1; > } > > -static __always_inline int arch_spin_is_contended(arch_spinlock_t *lock) > +static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock) > { > - u32 val = atomic_read(lock); > + u32 val = lock.counter; > > - return (s16)((val >> 16) - (val & 0xffff)) > 1; > + return ((val >> 16) == (val & 0xffff)); > } > > -static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock) > +static __always_inline int arch_spin_is_locked(arch_spinlock_t *lock) > { > - return !arch_spin_is_locked(&lock); > + arch_spinlock_t val = READ_ONCE(*lock); > + > + return !arch_spin_value_unlocked(val); > } > > #include <asm/qrwlock.h> > -- Best Regards Guo Ren ML: https://lore.kernel.org/linux-csky/ _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv
next prev parent reply other threads:[~2022-07-04 11:10 UTC|newest] Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-06-28 8:17 [PATCH V7 0/5] riscv: Add qspinlock support with combo style guoren 2022-06-28 8:17 ` guoren 2022-06-28 8:17 ` [PATCH V7 1/5] asm-generic: ticket-lock: Remove unnecessary atomic_read guoren 2022-06-28 8:17 ` guoren 2022-06-28 18:05 ` Waiman Long 2022-06-28 18:05 ` Waiman Long 2022-06-29 2:12 ` Guo Ren 2022-06-29 2:12 ` Guo Ren 2022-06-29 8:27 ` David Laight 2022-06-29 8:27 ` David Laight 2022-07-01 15:18 ` Guo Ren 2022-07-01 15:18 ` Guo Ren 2022-07-04 9:52 ` Peter Zijlstra 2022-07-04 9:52 ` Peter Zijlstra 2022-07-04 11:10 ` Guo Ren [this message] 2022-07-04 11:10 ` Guo Ren 2022-06-28 8:17 ` [PATCH V7 2/5] asm-generic: ticket-lock: Use the same struct definitions with qspinlock guoren 2022-06-28 8:17 ` guoren 2022-06-28 8:17 ` [PATCH V7 3/5] asm-generic: ticket-lock: Move into ticket_spinlock.h guoren 2022-06-28 8:17 ` guoren 2022-06-28 8:17 ` [PATCH V7 4/5] asm-generic: spinlock: Add combo spinlock (ticket & queued) guoren 2022-06-28 8:17 ` guoren 2022-06-28 18:13 ` Waiman Long 2022-06-28 18:13 ` Waiman Long 2022-06-29 1:17 ` Guo Ren 2022-06-29 1:17 ` Guo Ren 2022-06-29 1:34 ` Waiman Long 2022-06-29 1:34 ` Waiman Long 2022-06-29 2:29 ` Guo Ren 2022-06-29 2:29 ` Guo Ren 2022-06-29 7:08 ` Arnd Bergmann 2022-06-29 7:08 ` Arnd Bergmann 2022-06-29 8:24 ` Guo Ren 2022-06-29 8:24 ` Guo Ren 2022-06-29 8:29 ` Arnd Bergmann 2022-06-29 8:29 ` Arnd Bergmann 2022-07-01 12:18 ` Guo Ren 2022-07-01 12:18 ` Guo Ren 2022-06-29 12:53 ` Waiman Long 2022-06-29 12:53 ` Waiman Long 2022-07-04 9:57 ` Peter Zijlstra 2022-07-04 9:57 ` Peter Zijlstra 2022-07-04 13:13 ` Guo Ren 2022-07-04 13:13 ` Guo Ren 2022-07-04 13:45 ` Peter Zijlstra 2022-07-04 13:45 ` Peter Zijlstra 2022-06-28 8:17 ` [PATCH V7 5/5] riscv: Add qspinlock support guoren 2022-06-28 8:17 ` guoren
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