A mapping of places manipulating the mp_lock in the SMP kernel

===============================================================================
This mapping is relative to the 3.0-current srs/sys tree as of 970430.  It
is meant to give an idea of where we currently use the "giant lock"
to enforce kernel integrity.  It is from this point that we will start to
"push down" the lock into the various sub-systems within the kernel.
It is anticipated that this will be done to the syscall, trap and interrupt
handler entry points.

===============================================================================
get_mplock occurs in:

/usr/SMP/src/sys/i386/i386/exception.s
/usr/SMP/src/sys/i386/i386/mplock.s
/usr/SMP/src/sys/i386/include/smp.h
/usr/SMP/src/sys/i386/isa/vector.s
/usr/SMP/src/sys/kern/init_smp.c


===============================================================================
rel_mplock occurs in:

/usr/SMP/src/sys/i386/i386/mplock.s
/usr/SMP/src/sys/i386/include/smp.h
/usr/SMP/src/sys/i386/isa/icu.s
/usr/SMP/src/sys/i386/isa/vector.s
/usr/SMP/src/sys/kern/init_smp.c


===============================================================================
_MPgetlock and _MPrellock occur in:

/usr/SMP/src/sys/i386/i386/mplock.s


===============================================================================
mp_lock occurs in:

/usr/SMP/src/sys/i386/i386/mp_machdep.c
/usr/SMP/src/sys/i386/i386/mplock.s
/usr/SMP/src/sys/i386/i386/swtch.s
/usr/SMP/src/sys/i386/include/smp.h
/usr/SMP/src/sys/kern/init_smp.c


===============================================================================
merged list of occurrances:

/usr/SMP/src/sys/i386/include/smp.h

/usr/SMP/src/sys/kern/init_smp.c

/usr/SMP/src/sys/i386/isa/icu.s
/usr/SMP/src/sys/i386/isa/vector.s

/usr/SMP/src/sys/i386/i386/exception.s
/usr/SMP/src/sys/i386/i386/mp_machdep.c
/usr/SMP/src/sys/i386/i386/mplock.s
/usr/SMP/src/sys/i386/i386/swtch.s


===============================================================================
/usr/SMP/src/sys/i386/include/smp.h

extern u_int			mp_lock;
void	get_mplock		__P((void));
void	rel_mplock		__P((void));
void	try_mplock		__P((void));


===============================================================================
/usr/SMP/src/sys/kern/init_smp.c

----------------
secondary_main()
{
	get_mplock();
 ...
	curproc = NULL;			/* ensure no context to save */
	cpu_switch(curproc);		/* start first process */
	panic("switch returned!");
}

---
smp_idleloop()
{
 ...
	spl0();
	rel_mplock();

	while (1) {
		if (smp_cpus == 0 && smp_active != 0) {
			get_mplock();
 ...
			rel_mplock();
		}

		if (smp_active && smp_active <= cpunumber()) {
			get_mplock();
 ... [ FREEZE ]
			rel_mplock();
 ... [ cpu spins ]
			get_mplock();
 ... [ UNFREEZE ]
			rel_mplock();
		}
			
		if (whichqs || whichrtqs || (!ignore_idleprocs && whichidqs)) {
			get_mplock();
			if (whichqs || whichrtqs ||
					(!ignore_idleprocs && whichidqs)) {
				splhigh();
				if (curproc)
					setrunqueue(curproc);
				cnt.v_swtch++;
				cpu_switch(curproc);
				microtime(&runtime);
				(void)spl0();
			}
			rel_mplock();
		} else {
			dcnt++;
			if (idle_debug && (dcnt % idle_debug) == 0) {
				get_mplock();
				printf( ... );
				rel_mplock();
			}
		}
	}
}

===============================================================================
/usr/SMP/src/sys/i386/isa/icu.s

--------
_doreti:
 ...
doreti_next:
 ...
	cli
	andl	_ipending,%ecx
	jne	doreti_unpend
doreti_exit:
	movl	%eax,_cpl
	decb	_intr_nesting_level
	MEXITCOUNT
#ifdef SMP 
	call	_rel_mplock
#endif	/* SMP */
 ...
doreti_iret:
	iret
 ...
doreti_unpend:
	sti
	bsfl	%ecx,%ecx		/* slow, but not worth optimizing */
#ifdef SMP
	lock
#endif
	btrl	%ecx,_ipending
	jnc	doreti_next		/* some intr cleared memory copy */
	movl	ihandlers(,%ecx,4),%edx
	testl	%edx,%edx
	je	doreti_next		/* "can't happen" */
	cmpl	$NHWI,%ecx
	jae	doreti_swi
	cli
	movl	%eax,_cpl
	MEXITCOUNT
	jmp	%edx

doreti_swi:
 ...
	jmp	doreti_next

swi_ast:
	addl	$8,%esp			/* discard raddr & cpl to get trap frame */
	testb	$SEL_RPL_MASK,TRAPF_CS_OFF(%esp)
	je	swi_ast_phantom
 ...
	jmp	doreti_next

swi_ast_phantom:
 ...
	cli
#ifdef SMP
	lock
#endif
 ...
	jmp	doreti_exit	/* SWI_AST is highest so we must be done */


===============================================================================
/usr/SMP/src/sys/i386/isa/vector.s

---
#define GET_MPLOCK	call _get_mplock
#define REL_MPLOCK	call _rel_mplock

---
#define MAYBE_MASK_IRQ(irq_num,icu)					\
	testl	$IRQ_BIT(irq_num),iactive ;	/* lazy masking */	\
	je	1f ;			/* NOT currently active */	\
 ...
	REL_MPLOCK ;			/* SMP release global lock */	\
 ...
	iret ;								\
1: ;									\
	orl	$IRQ_BIT(irq_num),iactive

---
#define	FAST_INTR(irq_num, vec_name, enable_icus) \
IDTVEC(vec_name) ; \
 ...
	GET_MPLOCK ;		/* SMP Spin lock */ \
	pushl	_intr_unit + (irq_num) * 4 ; \
	call	*_intr_handler + (irq_num) * 4 ; /* do the work ASAP */ \
 ...
	andl	_ipending,%eax ; \
	jne	2f ; 		/* yes, maybe handle them */ \
1: ; \
	REL_MPLOCK ;		/* SMP release global lock */ \
 ...
	iret ; \
2: ; \
 ...
	jmp	_doreti

---
#define	INTR(irq_num, vec_name, icu, enable_icus, reg) \
IDTVEC(vec_name) ; \
 ...
	GET_MPLOCK ;		/* SMP Spin lock */ \
	MAYBE_MASK_IRQ(irq_num,icu) ; \
	enable_icus ; \
	movl	_cpl,%eax ; \
	TEST_IRQ(irq_num,reg) ; \
	jne	2f ; \
	incb	_intr_nesting_level ; \
__CONCAT(Xresume,irq_num): ; \
 ...
	movl	%eax,_cpl ; \
	sti ; \
	call	*_intr_handler + (irq_num) * 4 ; \
	cli ;			/* must unmask _imen and icu atomically */ \
	MAYBE_UNMASK_IRQ(irq_num,icu) ; \
	sti ;			/* XXX _doreti repeats the cli/sti */ \
 ...
	jmp	_doreti ; \
2: ; \
 ...
	REL_MPLOCK ;		/* SMP release global lock */  \
 ...
	iret

===============================================================================
/usr/SMP/src/sys/i386/i386/exception.s

-----------
IDTVEC(fpu)
 ...
	pushl	$0		/* dummy unit to finish building intr frame */
#ifdef SMP
	call	_get_mplock
#endif /* SMP */
	incl	_cnt+V_TRAP
	orl	$SWI_AST_MASK,%eax
	movl	%eax,_cpl
	call	_npxintr
	incb	_intr_nesting_level
	MEXITCOUNT
	jmp	_doreti

-------------
IDTVEC(align)
 ...
calltrap:
#ifdef SMP
	call	_get_mplock
#endif /* SMP */
	FAKE_MCOUNT(_btrap)			/* init "from" _btrap -> calltrap */
	incl	_cnt+V_TRAP
	orl	$SWI_AST_MASK,_cpl
	call	_trap
 ...
	pushl	%eax
	subl	$4,%esp
	incb	_intr_nesting_level
	MEXITCOUNT
	jmp	_doreti

---------------
IDTVEC(syscall)
 ...
#ifdef SMP
	call	_get_mplock
#endif /* SMP */
	incl	_cnt+V_SYSCALL
	movl	$SWI_AST_MASK,_cpl
	call	_syscall
	/*
	 * Return via _doreti to handle ASTs.
	 */
	pushl	$0				/* cpl to restore */
	subl	$4,%esp
	movb	$1,_intr_nesting_level
	MEXITCOUNT
	jmp	_doreti

-----------------------
IDTVEC(int0x80_syscall)
 ...
#ifdef SMP
	call	_get_mplock
#endif /* SMP */
	incl	_cnt+V_SYSCALL
	movl	$SWI_AST_MASK,_cpl
	call	_syscall
	/*
	 * Return via _doreti to handle ASTs.
	 */
	pushl	$0				/* cpl to restore */
	subl	$4,%esp
	movb	$1,_intr_nesting_level
	MEXITCOUNT
	jmp	_doreti


===============================================================================
/usr/SMP/src/sys/i386/i386/machdep.c

init386(first)
	int first;
{
 ...
	/* setup proc 0's pcb */
 ...
	proc0.p_addr->u_pcb.pcb_mpnest = 1;
}


===============================================================================
/usr/SMP/src/sys/i386/i386/mp_machdep.c

startAllAPs( u_int bootAddr )
{
 ...
     * get the initial mp_lock with a count of 1 for the BSP
     */
    mp_lock = (apic_base[ APIC_ID ] & APIC_ID_MASK) + 1;
 ...
}


===============================================================================
/usr/SMP/src/sys/i386/i386/mplock.s

NON_GPROF_ENTRY(MPgetlock)
 ...

NON_GPROF_ENTRY(MPrellock)
 ...

NON_GPROF_ENTRY(get_mplock)
 ...

NON_GPROF_ENTRY(rel_mplock)
 ...


===============================================================================
/usr/SMP/src/sys/i386/i386/swtch.s

ENTRY(cpu_switch)
 ...
	testl	%ecx,%ecx
	je	sw1

#ifdef SMP
	movb	P_ONCPU(%ecx), %al		/* save "last" cpu */
	movb	%al, P_LASTCPU(%ecx)
	movb	$0xff, P_ONCPU(%ecx)		/* "leave" the cpu */
#endif
 ...
#ifdef SMP
	movl	_mp_lock, %eax
	cmpl	$0xffffffff, %eax		/* is it free? */
	je	badsw				/* yes, bad medicine! */
	andl	$0x00ffffff, %eax		/* clear CPU portion */
	movl	%eax,PCB_MPNEST(%ecx)		/* store it */
#endif /* SMP */
 ...
	movb	$1,_intr_nesting_level		/* charge Intr, not Sys/Idle */
	SETCURPROC($0, %edi)
sw1:
	cli

 ......

	movb	$0,_intr_nesting_level
#ifdef SMP
	movl	_apic_base, %eax		/* base addr of LOCAL APIC */
 ...
	movl	APIC_ID(%eax), %eax		/* APIC ID register */
	andl	$APIC_ID_MASK, %eax		/* extract ID portion */
	orl	PCB_MPNEST(%edx), %eax		/* add count from PROC */
	movl	%eax, _mp_lock			/* load the mp_lock */
#endif /* SMP */
 ...
	sti
	ret


===============================================================================