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Date:      Fri, 8 Feb 2008 09:17:15 GMT
From:      Warner Losh <imp@FreeBSD.org>
To:        Perforce Change Reviews <perforce@freebsd.org>
Subject:   PERFORCE change 135027 for review
Message-ID:  <200802080917.m189HF0o016528@repoman.freebsd.org>
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http://perforce.freebsd.org/chv.cgi?CH=135027

Change 135027 by imp@imp_lighthouse on 2008/02/08 09:16:43

	First cut at implementing gonzo's suggestions for AST handling.

Affected files ...

.. //depot/projects/mips2-jnpr/src/sys/mips/include/asm.h#10 edit
.. //depot/projects/mips2-jnpr/src/sys/mips/mips/exception.S#12 edit
.. //depot/projects/mips2-jnpr/src/sys/mips/mips/genassym.c#6 edit
.. //depot/projects/mips2-jnpr/src/sys/mips/mips/swtch.S#13 edit
.. //depot/projects/mips2-jnpr/src/sys/mips/mips/trap.c#10 edit

Differences ...

==== //depot/projects/mips2-jnpr/src/sys/mips/include/asm.h#10 (text+ko) ====

@@ -304,6 +304,26 @@
 	.align	3
 
 /*
+ * Call ast if required
+ */
+#define DO_AST							\
+	GET_CPU_PCPU(k1)					\
+	lw	k1, PC_CURTHREAD(k1);				\
+	lw	t0, TD_FLAGS(k1);				\
+	and	t0, t0, (TDF_ASTPENDING|TDF_NEEDRESCHED);	\
+	beq	t0, zero, 27f;					\
+	nop;							\
+	lw	k1, TD_FRAME(k1);				\
+	lw	t0, TF_REG_SR(k1);				\
+	and	t0, t0, SR_KSU_USER;				\
+	beq	t0, zero, 27f;					\
+	nop;							\
+	move	a0, k1;						\
+	jal	ast;						\
+	nop;							\
+27:					
+
+/*
  * XXX retain dialects XXX
  */
 #define	ALEAF(x)			XLEAF(x)

==== //depot/projects/mips2-jnpr/src/sys/mips/mips/exception.S#12 (text+ko) ====

@@ -382,10 +382,14 @@
 	jalr	k0
 	sw	a3, STAND_RA_OFFSET + KERN_REG_SIZE(sp)		# for debugging
 
+	.set	at
+	/* A call to AST would step on v0, I think, do we need to save it? */
+	DO_AST
+	.set	noat
+
 	RESTORE_CPU			# v0 contains the return address.
 	sync
 	eret
-
 	.set	at
 END(MipsKernGenException)
 
@@ -581,6 +585,7 @@
 	la	k0, _C_LABEL(cpu_intr)
 	jalr	k0
 	sw	a3, STAND_RA_OFFSET + KERN_REG_SIZE(sp)
+	/* Why no AST processing here? */
 /*
  * Restore registers and return from the interrupt.
  */
@@ -666,6 +671,7 @@
 	jalr	k0
 	sw	a3, STAND_RA_OFFSET(sp)	# for debugging
 
+	DO_AST
 /*
  * Since interrupts are enabled at this point, we use a1 instead of
  * k0 or k1 to store the PCB pointer.  This is because k0 and k1

==== //depot/projects/mips2-jnpr/src/sys/mips/mips/genassym.c#6 (text+ko) ====

@@ -68,6 +68,9 @@
 ASSYM(TD_REALKSTACK, offsetof(struct thread, td_md.md_realstack));
 ASSYM(TD_FLAGS, offsetof(struct thread, td_flags));
 ASSYM(TD_LOCK, offsetof(struct thread, td_lock));
+ASSYM(TD_FRAME, offsetof(struct thread, td_frame));
+
+ASSYM(TF_REG_SR, offsetof(struct trapframe, sr));
 
 ASSYM(U_PCB_REGS, offsetof(struct pcb, pcb_regs.zero));
 ASSYM(U_PCB_CONTEXT, offsetof(struct pcb, pcb_context));

==== //depot/projects/mips2-jnpr/src/sys/mips/mips/swtch.S#13 (text+ko) ====

@@ -161,6 +161,8 @@
 	jal	_C_LABEL(fork_exit)
 	move	a2,s2			  #BDSlot
 
+	DO_AST
+
 /*
  * Since interrupts are enabled at this point, we use a1 instead of
  * k0 or k1 to store the PCB pointer.  This is because k0 and k1

==== //depot/projects/mips2-jnpr/src/sys/mips/mips/trap.c#10 (text+ko) ====

@@ -828,49 +828,6 @@
 
 		PTRACESTOP_SC(p, td, S_PT_SCX);
 
-		/*
-		 * XXX ast still need to happen
-		 *
-		 * Mail from jhb@:
-		 *
-		 * ast() is also still relevant in 7 as well.  What
-		 * normally happens is that you have the following in
-		 * assembly:
-		 * 
-		 * trap_entry:
-		 *	setup regs
-		 *	call trap
-		 *	jmp  exittrap
-		 *
-		 * syscall_entry:
-		 *	setup regs
-		 *	call syscall
-		 *	jmp  exittrap
-		 *
-		 * exittrap:
-		 *	get ready to return from trap
-		 *	disable interrupts
-		 *	if returning to kernel jmp kernel
-		 * asts:
-		 *	if no ASTs are pending jmp kernel
-		 *	enable interrupts
-		 *	call ast
-		 *	disable interrupts
-		 *	jmp asts
-		 * kernel:
-		 *	restore registers
-		 *	reti
-		 *
-		 * or some such.  You could do it in C if you wanted,
-		 * but the idea is you want to only return to userland
-		 * once you've verified you have no ASTs with
-		 * interrupts disabled.  If you get any AST's while
-		 * returning to userland it's due to SMP and you will
-		 * get an IPI that will post with 'reti' finishes.
-		 */
-		if (curthread->td_flags & (TDF_ASTPENDING|TDF_NEEDRESCHED)) {
-			ast(trapframe);
-		}
 		return (trapframe->pc);
 	    }

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