Changeset 8937f12 in rtems

Timestamp:

May 31, 2020, 2:22:54 PM (11 months ago)

Author:

Jan Sommer <jan.sommer@…>

Branches:

5, master

Children:

5d4a1edc

Parents:

85d6a760

git-author:

Jan Sommer <jan.sommer@…> (05/31/20 14:22:54)

git-committer:

Chris Johns <chrisj@…> (06/11/20 03:29:03)

Message:

bsp/pc386: Update context switch and restore

Uses similar flow in cpu_asm.S for i386 as for arm.

Location:

cpukit/score/cpu/i386

Files:

• cpu_asm.S (modified) (3 diffs)
• include/rtems/score/cpu.h (modified) (2 diffs)

cpukit/score/cpu/i386/cpu_asm.S

@@ -52 +52 @@
 SYM (_CPU_Context_switch):
         movl      RUNCONTEXT_ARG(esp),eax  /* eax = running threads context */
+        GET_SELF_CPU_CONTROL edx           /* edx has address for per_CPU information */
+        movl      PER_CPU_ISR_DISPATCH_DISABLE(edx),ecx
         pushf                              /* push eflags */
         popl      REG_EFLAGS(eax)          /* save eflags */
@@ -59 +61 @@
         movl      esi,REG_ESI(eax)         /* save source register */
         movl      edi,REG_EDI(eax)         /* save destination register */
+        movl      ecx, I386_CONTEXT_CONTROL_ISR_DISPATCH_DISABLE(eax)
+
+        movl      eax,ecx                  /* ecx = running threads context */
+        movl      HEIRCONTEXT_ARG(esp),eax /* eax = heir threads context */
 
 #ifdef RTEMS_SMP
-        /* The executing context no longer executes on this processor */
-        movb      $0, I386_CONTEXT_CONTROL_IS_EXECUTING_OFFSET(eax)
-#endif
-
-        movl      HEIRCONTEXT_ARG(esp),eax /* eax = heir threads context */
-
-#ifdef RTEMS_SMP
-        /* Wait for heir context to stop execution */
-1:
-        movb      I386_CONTEXT_CONTROL_IS_EXECUTING_OFFSET(eax), bl
-        testb     bl, bl
-        jne       1b
-
-        /* The heir context executes now on this processor */
-        movb      $1, I386_CONTEXT_CONTROL_IS_EXECUTING_OFFSET(eax)
-#endif
-
-restore:
+      /*
+       * The executing thread no longer executes on this processor.  Switch
+       * the stack to the temporary interrupt stack of this processor.  Mark
+       * the context of the executing thread as not executing.
+       */
+        leal      PER_CPU_INTERRUPT_FRAME_AREA + CPU_INTERRUPT_FRAME_SIZE(edx),esp
+        movb      $0, I386_CONTEXT_CONTROL_IS_EXECUTING_OFFSET(ecx)
+
+.L_check_is_executing:
+        lock bts  $0,I386_CONTEXT_CONTROL_IS_EXECUTING_OFFSET(eax)  /* Indicator in carry flag */
+        jc        .L_get_potential_new_heir
+#endif
+
+/* Start restoring context */
+.L_restore:
+        movl      I386_CONTEXT_CONTROL_ISR_DISPATCH_DISABLE(eax),ecx
+        movl      ecx,PER_CPU_ISR_DISPATCH_DISABLE(edx)
         pushl     REG_EFLAGS(eax)          /* push eflags */
         popf                               /* restore eflags */
@@ -111 +116 @@
 SYM (_CPU_Context_restore):
         movl      NEWCONTEXT_ARG(esp),eax  /* eax = running threads context */
-        jmp       restore
+        GET_SELF_CPU_CONTROL edx           /* edx has address for per_CPU information */
+        jmp       .L_restore
+
+#ifdef RTEMS_SMP
+
+.L_get_potential_new_heir:
+
+        /* We may have a new heir */
+
+        /* Read the executing and heir */
+        movl    PER_CPU_OFFSET_EXECUTING(edx),ebx
+        movl    PER_CPU_OFFSET_HEIR(edx),esi
+
+        /*
+         * Update the executing only if necessary to avoid cache line
+         * monopolization.
+         */
+        cmp     esi,ebx
+        je      .L_check_is_executing
+
+        /* Calculate the heir context pointer */
+        addl    esi,eax
+        subl    ebx,eax
+
+        /* Update the executing */
+        movl    esi,PER_CPU_OFFSET_EXECUTING(edx)
+
+        jmp     .L_check_is_executing
+#endif
 
 /*void _CPU_Context_save_fp_context( &fp_context_ptr )

cpukit/score/cpu/i386/include/rtems/score/cpu.h

@@ -116 +116 @@
 #define I386_CONTEXT_CONTROL_GS_0_OFFSET 24
 #define I386_CONTEXT_CONTROL_GS_1_OFFSET 28
+#define I386_CONTEXT_CONTROL_ISR_DISPATCH_DISABLE 32
 
 #ifdef RTEMS_SMP
-  #define I386_CONTEXT_CONTROL_IS_EXECUTING_OFFSET 32
+  #define I386_CONTEXT_CONTROL_IS_EXECUTING_OFFSET 36
 #endif
 
@@ -137 +138 @@
   uint32_t    edi;        /* extended destination index flags register */
   segment_descriptors gs; /* gs segment descriptor                     */
+  uint32_t isr_dispatch_disable;
 #ifdef RTEMS_SMP
   volatile bool is_executing;