OS-7753 THREAD_KPRI_RELEASE does nothing of the sort
Reviewed by: Bryan Cantrill <bryan@joyent.com>
Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>

@@ -19,14 +19,13 @@
  * CDDL HEADER END
  */
 /*
  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
+ * Copyright 2019 Joyent, Inc.
  */
 
-#pragma ident   "%Z%%M% %I%     %E% SMI"
-
 #if defined(lint) || defined(__lint)
 #include <sys/types.h>
 #include <sys/thread.h>
 #include <sys/cpuvar.h>
 #include <vm/page.h>

@@ -916,14 +915,12 @@
 #else   /* __lint */
 
 #if defined(__amd64)
 
         ENTRY(rw_enter)
-        movq    %gs:CPU_THREAD, %rdx            /* rdx = thread ptr */
         cmpl    $RW_WRITER, %esi
         je      .rw_write_enter
-        incl    T_KPRI_REQ(%rdx)                /* THREAD_KPRI_REQUEST() */
         movq    (%rdi), %rax                    /* rax = old rw_wwwh value */
         testl   $RW_WRITE_LOCKED|RW_WRITE_WANTED, %eax
         jnz     rw_enter_sleep
         leaq    RW_READ_LOCK(%rax), %rdx        /* rdx = new rw_wwwh value */
         lock

@@ -935,10 +932,11 @@
         movq    %rdi, %rsi                      /* rsi = lock ptr */
         movl    $LS_RW_ENTER_ACQUIRE, %edi
         movl    $RW_READER, %edx
         jmp     lockstat_wrapper_arg
 .rw_write_enter:
+        movq    %gs:CPU_THREAD, %rdx
         orq     $RW_WRITE_LOCKED, %rdx          /* rdx = write-locked value */
         xorl    %eax, %eax                      /* rax = unheld value */
         lock
         cmpxchgq %rdx, (%rdi)                   /* try to grab write lock */
         jnz     rw_enter_sleep

@@ -970,14 +968,13 @@
         xorl    %edx, %edx                      /* rdx = new value (unheld) */
 .rw_read_exit:
         lock
         cmpxchgq %rdx, (%rdi)                   /* try to drop read lock */
         jnz     rw_exit_wakeup
-        movq    %gs:CPU_THREAD, %rcx            /* rcx = thread ptr */
-        decl    T_KPRI_REQ(%rcx)                /* THREAD_KPRI_RELEASE() */
 .rw_read_exit_lockstat_patch_point:
         ret
+        movq    %gs:CPU_THREAD, %rcx            /* rcx = thread ptr */
         movq    %rdi, %rsi                      /* rsi = lock ptr */
         movl    $LS_RW_EXIT_RELEASE, %edi
         movl    $RW_READER, %edx
         jmp     lockstat_wrapper_arg
 .rw_not_single_reader:

@@ -1004,15 +1001,13 @@
         SET_SIZE(rw_exit)
 
 #else
 
         ENTRY(rw_enter)
-        movl    %gs:CPU_THREAD, %edx            /* edx = thread ptr */
         movl    4(%esp), %ecx                   /* ecx = lock ptr */
         cmpl    $RW_WRITER, 8(%esp)
         je      .rw_write_enter
-        incl    T_KPRI_REQ(%edx)                /* THREAD_KPRI_REQUEST() */
         movl    (%ecx), %eax                    /* eax = old rw_wwwh value */
         testl   $RW_WRITE_LOCKED|RW_WRITE_WANTED, %eax
         jnz     rw_enter_sleep
         leal    RW_READ_LOCK(%eax), %edx        /* edx = new rw_wwwh value */
         lock

@@ -1023,10 +1018,11 @@
         movl    %gs:CPU_THREAD, %edx            /* edx = thread ptr */
         movl    $LS_RW_ENTER_ACQUIRE, %eax
         pushl   $RW_READER
         jmp     lockstat_wrapper_arg
 .rw_write_enter:
+        movl    %gs:CPU_THREAD, %edx
         orl     $RW_WRITE_LOCKED, %edx          /* edx = write-locked value */
         xorl    %eax, %eax                      /* eax = unheld value */
         lock
         cmpxchgl %edx, (%ecx)                   /* try to grab write lock */
         jnz     rw_enter_sleep

@@ -1058,12 +1054,10 @@
         xorl    %edx, %edx                      /* edx = new value (unheld) */
 .rw_read_exit:
         lock
         cmpxchgl %edx, (%ecx)                   /* try to drop read lock */
         jnz     rw_exit_wakeup
-        movl    %gs:CPU_THREAD, %edx            /* edx = thread ptr */
-        decl    T_KPRI_REQ(%edx)                /* THREAD_KPRI_RELEASE() */
 .rw_read_exit_lockstat_patch_point:
         ret
         movl    $LS_RW_EXIT_RELEASE, %eax
         pushl   $RW_READER
         jmp     lockstat_wrapper_arg