[PATCH REBASED 4/6] x86: Add __down_read_killable()

Kirill Tkhai
2017-09-29T16:06:28Z

Similar to __down_write_killable(), add read killable primitive:
extract current __down_read() code to macros and teach it to get
different functions as slow_path argument:
store ax register to ret, and add sp register and preserve its value.

Add call_rwsem_down_read_failed_killable() assembly entry similar
to call_rwsem_down_read_failed():
push dx register to stack in additional to common registers,
as it's not declarated as modifiable in ____down_read().

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
arch/x86/include/asm/rwsem.h | 35 +++++++++++++++++++++++++----------
arch/x86/lib/rwsem.S | 12 ++++++++++++
2 files changed, 37 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
index a8f486e7a124..1e51195c0b63 100644
--- a/arch/x86/include/asm/rwsem.h
+++ b/arch/x86/include/asm/rwsem.h
@@ -60,18 +60,33 @@
/*
* lock for reading
*/
+#define ____down_read(sem, slow_path) \
+({ \
+ struct rw_semaphore* ret; \
+ asm volatile("# beginning down_read\n\t" \
+ LOCK_PREFIX _ASM_INC "(%[sem])\n\t" \
+ /* adds 0x00000001 */ \
+ " jns 1f\n" \
+ " call " slow_path "\n" \
+ "1:\n\t" \
+ "# ending down_read\n\t" \
+ : "+m" (sem->count), "=a" (ret), \
+ ASM_CALL_CONSTRAINT \
+ : [sem] "a" (sem) \
+ : "memory", "cc"); \
+ ret; \
+})
+
static inline void __down_read(struct rw_semaphore *sem)
{
- asm volatile("# beginning down_read\n\t"
- LOCK_PREFIX _ASM_INC "(%[sem])\n\t"
- /* adds 0x00000001 */
- " jns 1f\n"
- " call call_rwsem_down_read_failed\n"
- "1:\n\t"
- "# ending down_read\n\t"
- : "+m" (sem->count)
- : [sem] "a" (sem)
- : "memory", "cc");
+ ____down_read(sem, "call_rwsem_down_read_failed");
+}
+
+static inline int __down_read_killable(struct rw_semaphore *sem)
+{
+ if (IS_ERR(____down_read(sem, "call_rwsem_down_read_failed_killable")))
+ return -EINTR;
+ return 0;
}

/*
diff --git a/arch/x86/lib/rwsem.S b/arch/x86/lib/rwsem.S
index bf2c6074efd2..dc2ab6ea6768 100644
--- a/arch/x86/lib/rwsem.S
+++ b/arch/x86/lib/rwsem.S
@@ -98,6 +98,18 @@ ENTRY(call_rwsem_down_read_failed)
ret
ENDPROC(call_rwsem_down_read_failed)

+ENTRY(call_rwsem_down_read_failed_killable)
+ FRAME_BEGIN
+ save_common_regs
+ __ASM_SIZE(push,) %__ASM_REG(dx)
+ movq %rax,%rdi
+ call rwsem_down_read_failed_killable
+ __ASM_SIZE(pop,) %__ASM_REG(dx)
+ restore_common_regs
+ FRAME_END
+ ret
+ENDPROC(call_rwsem_down_read_failed_killable)
+
ENTRY(call_rwsem_down_write_failed)
FRAME_BEGIN
save_common_regs