[Devel] [PATCH RHEL7 COMMIT] locking/arch, x86: Add __down_read_killable()

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-1127.8.2.vz7.161.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1127.8.2.vz7.161.1
------>
commit db16e9c0f570a642cbbb259beaa269f66f6e8558
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Mon May 25 17:55:58 2020 +0300

    locking/arch, x86: Add __down_read_killable()
    
    ms commit 19c60923010b
    
    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 at virtuozzo.com>
    
    Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
    Cc: Linus Torvalds <torvalds at linux-foundation.org>
    Cc: Peter Zijlstra <peterz at infradead.org>
    Cc: Thomas Gleixner <tglx at linutronix.de>
    Cc: arnd at arndb.de
    Cc: avagin at virtuozzo.com
    Cc: davem at davemloft.net
    Cc: fenghua.yu at intel.com
    Cc: gorcunov at virtuozzo.com
    Cc: heiko.carstens at de.ibm.com
    Cc: hpa at zytor.com
    Cc: ink at jurassic.park.msu.ru
    Cc: mattst88 at gmail.com
    Cc: rientjes at google.com
    Cc: rth at twiddle.net
    Cc: schwidefsky at de.ibm.com
    Cc: tony.luck at intel.com
    Cc: viro at zeniv.linux.org.uk
    Link: http://lkml.kernel.org/r/150670118802.23930.1316107715255410256.stgit@localhost.localdomain
    Signed-off-by: Ingo Molnar <mingo at kernel.org>
    
    =====================
    Patchset description:
    
    This ports support for down_read_killable(),
    which is a prerequisite for pernet_ops_rwsem.
    
    https://jira.sw.ru/browse/PSBM-104158
---
 arch/x86/include/asm/rwsem.h | 35 +++++++++++++++++++++++++----------
 arch/x86/lib/rwsem.S         | 15 +++++++++++++++
 2 files changed, 40 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
index ce4cc45576492..26cdc9b147d5c 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 880fcda587bf4..39736f7a82842 100644
--- a/arch/x86/lib/rwsem.S
+++ b/arch/x86/lib/rwsem.S
@@ -101,6 +101,21 @@ ENTRY(call_rwsem_down_read_failed)
 	CFI_ENDPROC
 ENDPROC(call_rwsem_down_read_failed)
 
+ENTRY(call_rwsem_down_read_failed_killable)
+	CFI_STARTPROC
+	FRAME_BEGIN
+	save_common_regs
+	__ASM_SIZE(push,_cfi) %__ASM_REG(dx)
+	movq %rax,%rdi
+	call rwsem_down_read_failed_killable
+	__ASM_SIZE(pop,_cfi) %__ASM_REG(dx)
+	CFI_RESTORE __ASM_REG(dx)
+	restore_common_regs
+	FRAME_END
+	ret
+	CFI_ENDPROC
+ENDPROC(call_rwsem_down_read_failed_killable)
+
 ENTRY(call_rwsem_down_write_failed)
 	CFI_STARTPROC
 	FRAME_BEGIN