OK, so I have dropped patch 10 and reworked the x86 part to use the same asm as __down_write uses. Does this look any better?
I am not an expert in inline asm so the way I am doing it might be not optimal but at least the gerenated code looks sane (no changes for the regular __down_write). --- >From d9a24cd6d6eb48602b11df56ecc3ea4e223ac18d Mon Sep 17 00:00:00 2001 From: Michal Hocko <[email protected]> Date: Mon, 1 Feb 2016 18:21:51 +0100 Subject: [PATCH] x86, rwsem: provide __down_write_killable which uses the same fast path as __down_write except it falls back to call_rwsem_down_write_failed_killable slow path and return -EINTR if killed. To prevent from code duplication extract the skeleton of __down_write into a helper macro which just takes the semaphore and the slow path function to be called. Signed-off-by: Michal Hocko <[email protected]> --- arch/x86/include/asm/rwsem.h | 41 ++++++++++++++++++++++++++++------------- arch/x86/lib/rwsem.S | 8 ++++++++ 2 files changed, 36 insertions(+), 13 deletions(-) diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h index d79a218675bc..4c3d90dbe89a 100644 --- a/arch/x86/include/asm/rwsem.h +++ b/arch/x86/include/asm/rwsem.h @@ -99,21 +99,36 @@ static inline int __down_read_trylock(struct rw_semaphore *sem) /* * lock for writing */ +#define ____down_write(sem, slow_path) \ +({ \ + long tmp; \ + struct rw_semaphore* ret = sem; \ + asm volatile("# beginning down_write\n\t" \ + LOCK_PREFIX " xadd %1,(%2)\n\t" \ + /* adds 0xffff0001, returns the old value */ \ + " test " __ASM_SEL(%w1,%k1) "," __ASM_SEL(%w1,%k1) "\n\t" \ + /* was the active mask 0 before? */\ + " jz 1f\n" \ + " call " slow_path "\n" \ + "1:\n" \ + "# ending down_write" \ + : "+m" (sem->count), "=d" (tmp), "+a" (ret) \ + : "a" (sem), "1" (RWSEM_ACTIVE_WRITE_BIAS) \ + : "memory", "cc"); \ + ret; \ +}) + static inline void __down_write(struct rw_semaphore *sem) { - long tmp; - asm volatile("# beginning down_write\n\t" - LOCK_PREFIX " xadd %1,(%2)\n\t" - /* adds 0xffff0001, returns the old value */ - " test " __ASM_SEL(%w1,%k1) "," __ASM_SEL(%w1,%k1) "\n\t" - /* was the active mask 0 before? */ - " jz 1f\n" - " call call_rwsem_down_write_failed\n" - "1:\n" - "# ending down_write" - : "+m" (sem->count), "=d" (tmp) - : "a" (sem), "1" (RWSEM_ACTIVE_WRITE_BIAS) - : "memory", "cc"); + ____down_write(sem, "call_rwsem_down_write_failed"); +} + +static inline int __down_write_killable(struct rw_semaphore *sem) +{ + if (IS_ERR(____down_write(sem, "call_rwsem_down_write_failed_killable"))) + return -EINTR; + + return 0; } /* diff --git a/arch/x86/lib/rwsem.S b/arch/x86/lib/rwsem.S index 40027db99140..d1a1397e1fb3 100644 --- a/arch/x86/lib/rwsem.S +++ b/arch/x86/lib/rwsem.S @@ -101,6 +101,14 @@ ENTRY(call_rwsem_down_write_failed) ret ENDPROC(call_rwsem_down_write_failed) +ENTRY(call_rwsem_down_write_failed_killable) + save_common_regs + movq %rax,%rdi + call rwsem_down_write_failed_killable + restore_common_regs + ret +ENDPROC(call_rwsem_down_write_failed_killable) + ENTRY(call_rwsem_wake) /* do nothing if still outstanding active readers */ __ASM_HALF_SIZE(dec) %__ASM_HALF_REG(dx) -- 2.7.0 -- Michal Hocko SUSE Labs
