From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Date: Tue, 22 Mar 2022 11:54:37 -0400 Subject: [OpenRISC] [PATCH V2 1/5] asm-generic: ticket-lock: New generic ticket-based spinlock In-Reply-To: References: <20220319035457.2214979-1-guoren@kernel.org> <20220319035457.2214979-2-guoren@kernel.org> Message-ID: <54d6221d-0c4f-9329-042d-4f74c4ea288f@redhat.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: openrisc@lists.librecores.org On 3/21/22 23:10, Stafford Horne wrote: > Hello, > > There is a problem with this patch on Big Endian machines, see below. > > On Sat, Mar 19, 2022 at 11:54:53AM +0800, guoren at kernel.org wrote: >> From: Peter Zijlstra >> >> This is a simple, fair spinlock. Specifically it doesn't have all the >> subtle memory model dependencies that qspinlock has, which makes it more >> suitable for simple systems as it is more likely to be correct. >> >> [Palmer: commit text] >> Signed-off-by: Palmer Dabbelt >> >> -- >> >> I have specifically not included Peter's SOB on this, as he sent his >> original patch >> >> without one. >> --- >> include/asm-generic/spinlock.h | 11 +++- >> include/asm-generic/spinlock_types.h | 15 +++++ >> include/asm-generic/ticket-lock-types.h | 11 ++++ >> include/asm-generic/ticket-lock.h | 86 +++++++++++++++++++++++++ >> 4 files changed, 120 insertions(+), 3 deletions(-) >> create mode 100644 include/asm-generic/spinlock_types.h >> create mode 100644 include/asm-generic/ticket-lock-types.h >> create mode 100644 include/asm-generic/ticket-lock.h >> >> diff --git a/include/asm-generic/ticket-lock.h b/include/asm-generic/ticket-lock.h >> new file mode 100644 >> index 000000000000..59373de3e32a >> --- /dev/null >> +++ b/include/asm-generic/ticket-lock.h > ... > >> +static __always_inline void ticket_unlock(arch_spinlock_t *lock) >> +{ >> + u16 *ptr = (u16 *)lock + __is_defined(__BIG_ENDIAN); > As mentioned, this patch series breaks SMP on OpenRISC. I traced it to this > line. The above `__is_defined(__BIG_ENDIAN)` does not return 1 as expected > even on BIG_ENDIAN machines. This works: > > > diff --git a/include/asm-generic/ticket-lock.h b/include/asm-generic/ticket-lock.h > index 59373de3e32a..52b5dc9ffdba 100644 > --- a/include/asm-generic/ticket-lock.h > +++ b/include/asm-generic/ticket-lock.h > @@ -26,6 +26,7 @@ > #define __ASM_GENERIC_TICKET_LOCK_H > > #include > +#include > #include > > static __always_inline void ticket_lock(arch_spinlock_t *lock) > @@ -51,7 +52,7 @@ static __always_inline bool ticket_trylock(arch_spinlock_t *lock) > > static __always_inline void ticket_unlock(arch_spinlock_t *lock) > { > - u16 *ptr = (u16 *)lock + __is_defined(__BIG_ENDIAN); > + u16 *ptr = (u16 *)lock + IS_ENABLED(CONFIG_CPU_BIG_ENDIAN); > u32 val = atomic_read(lock); > > smp_store_release(ptr, (u16)val + 1); > > >> + u32 val = atomic_read(lock); >> + >> + smp_store_release(ptr, (u16)val + 1); >> +} >> + __BIG_ENDIAN is defined in . I believe that if you include , the second hunk is not really needed and vice versa. Cheers, Longman