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Implement an alternate method to stop CPUs when entering DDB. Normally we use

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a regular IPI vector, but this vector is blocked when interrupts are disabled.
With "options KDB_STOP_NMI" and debug.kdb.stop_cpus_with_nmi set, KDB will
send an NMI to each CPU instead. The code also has a context-stuffing
feature which helps ddb extract the state of processes running on the
stopped CPUs.

KDB_STOP_NMI is only useful with SMP and complains if SMP is not defined.
This feature only applies to i386 and amd64 at the moment, but could be
used on other architectures with the appropriate MD bits.

Submitted by:	ups
This commit is contained in:
Doug White 2005-04-30 20:01:00 +00:00
parent 6964622dd0
commit fdc9713bf7
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=145727
13 changed files with 274 additions and 0 deletions
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74
sys/amd64/amd64/mp_machdep.c
View file

@ -192,6 +192,10 @@ mp_topology(void)
}
#ifdef KDB_STOP_NMI
volatile cpumask_t ipi_nmi_pending;
#endif
/*
* Calculate usable address in base memory for AP trampoline code.
*/
@ -972,6 +976,76 @@ ipi_self(u_int ipi)
lapic_ipi_vectored(ipi, APIC_IPI_DEST_SELF);
}
#ifdef KDB_STOP_NMI
/*
* send NMI IPI to selected CPUs
*/
#define BEFORE_SPIN 1000000
void
ipi_nmi_selected(u_int32_t cpus)
{
int cpu;
register_t icrlo;
icrlo = APIC_DELMODE_NMI | APIC_DESTMODE_PHY | APIC_LEVEL_ASSERT
| APIC_TRIGMOD_EDGE;
CTR2(KTR_SMP, "%s: cpus: %x nmi", __func__, cpus);
atomic_set_int(&ipi_nmi_pending, cpus);
while ((cpu = ffs(cpus)) != 0) {
cpu--;
cpus &= ~(1 << cpu);
KASSERT(cpu_apic_ids[cpu] != -1,
("IPI NMI to non-existent CPU %d", cpu));
/* Wait for an earlier IPI to finish. */
if (!lapic_ipi_wait(BEFORE_SPIN))
panic("ipi_nmi_selected: previous IPI has not cleared");
lapic_ipi_raw(icrlo,cpu_apic_ids[cpu]);
}
}
int
ipi_nmi_handler()
{
int cpu = PCPU_GET(cpuid);
if(!(atomic_load_acq_int(&ipi_nmi_pending) & (1 << cpu)))
return 1;
atomic_clear_int(&ipi_nmi_pending,1 << cpu);
savectx(&stoppcbs[cpu]);
/* Indicate that we are stopped */
atomic_set_int(&stopped_cpus,1 << cpu);
/* Wait for restart */
while(!(atomic_load_acq_int(&started_cpus) & (1 << cpu)))
ia32_pause();
atomic_clear_int(&started_cpus,1 << cpu);
atomic_clear_int(&stopped_cpus,1 << cpu);
if(cpu == 0 && cpustop_restartfunc != NULL)
cpustop_restartfunc();
return 0;
}
#endif /* KDB_STOP_NMI */
/*
* This is called once the rest of the system is up and running and we're
* ready to let the AP's out of the pen.

8
sys/amd64/amd64/trap.c
View file

@ -165,6 +165,14 @@ trap(frame)
PCPU_LAZY_INC(cnt.v_trap);
type = frame.tf_trapno;
#ifdef KDB_STOP_NMI
/* Handler for NMI IPIs used for debugging */
if (type == T_NMI) {
if (ipi_nmi_handler() == 0)
goto out;
}
#endif /* KDB_STOP_NMI */
#ifdef KDB
if (kdb_active) {
kdb_reenter();

6
sys/amd64/conf/NOTES
View file

@ -33,6 +33,12 @@ device mptable # Optional MPSPEC mptable support
#
options MP_WATCHDOG
#
# Debugging options.
#
options KDB_STOP_NMI # Stop CPUS using NMI instead of IPI
#####################################################################
# CPU OPTIONS

5
sys/amd64/include/smp.h
View file

@ -63,6 +63,11 @@ void smp_masked_invlpg_range(u_int mask, vm_offset_t startva,
void smp_invltlb(void);
void smp_masked_invltlb(u_int mask);
#ifdef KDB_STOP_NMI
int ipi_nmi_handler(void);
void ipi_nmi_selected(u_int32_t cpus);
#endif
#endif /* !LOCORE */
#endif /* SMP */

3
sys/conf/options.amd64
View file

@ -55,3 +55,6 @@ PSM_HOOKRESUME opt_psm.h
PSM_RESETAFTERSUSPEND opt_psm.h
PSM_DEBUG opt_psm.h
DEV_ATPIC opt_atpic.h
# Debugging
KDB_STOP_NMI opt_global.h

3
sys/conf/options.i386
View file

@ -160,3 +160,6 @@ IPR_LOG opt_i4b.h
DEV_APIC opt_apic.h
DEV_NPX opt_npx.h
ASR_COMPAT opt_asr.h
# Debugging
KDB_STOP_NMI opt_global.h

5
sys/i386/conf/NOTES
View file

@ -51,6 +51,11 @@ options MPTABLE_FORCE_HTT # Enable HTT CPUs with the MP Table
#
options MP_WATCHDOG
# Debugging options.
#
options KDB_STOP_NMI # Stop CPUS using NMI instead of IPI
#####################################################################
# CPU OPTIONS

74
sys/i386/i386/mp_machdep.c
View file

@ -175,6 +175,10 @@ vm_offset_t smp_tlb_addr1;
vm_offset_t smp_tlb_addr2;
volatile int smp_tlb_wait;
#ifdef KDB_STOP_NMI
volatile cpumask_t ipi_nmi_pending;
#endif
/*
* Local data and functions.
*/
@ -1191,6 +1195,76 @@ ipi_self(u_int ipi)
lapic_ipi_vectored(ipi, APIC_IPI_DEST_SELF);
}
#ifdef KDB_STOP_NMI
/*
* send NMI IPI to selected CPUs
*/
#define BEFORE_SPIN 1000000
void
ipi_nmi_selected(u_int32_t cpus)
{
int cpu;
register_t icrlo;
icrlo = APIC_DELMODE_NMI | APIC_DESTMODE_PHY | APIC_LEVEL_ASSERT
| APIC_TRIGMOD_EDGE;
CTR2(KTR_SMP, "%s: cpus: %x nmi", __func__, cpus);
atomic_set_int(&ipi_nmi_pending, cpus);
while ((cpu = ffs(cpus)) != 0) {
cpu--;
cpus &= ~(1 << cpu);
KASSERT(cpu_apic_ids[cpu] != -1,
("IPI NMI to non-existent CPU %d", cpu));
/* Wait for an earlier IPI to finish. */
if (!lapic_ipi_wait(BEFORE_SPIN))
panic("ipi_nmi_selected: previous IPI has not cleared");
lapic_ipi_raw(icrlo,cpu_apic_ids[cpu]);
}
}
int
ipi_nmi_handler()
{
int cpu = PCPU_GET(cpuid);
if(!(atomic_load_acq_int(&ipi_nmi_pending) & (1 << cpu)))
return 1;
atomic_clear_int(&ipi_nmi_pending,1 << cpu);
savectx(&stoppcbs[cpu]);
/* Indicate that we are stopped */
atomic_set_int(&stopped_cpus,1 << cpu);
/* Wait for restart */
while(!(atomic_load_acq_int(&started_cpus) & (1 << cpu)))
ia32_pause();
atomic_clear_int(&started_cpus,1 << cpu);
atomic_clear_int(&stopped_cpus,1 << cpu);
if(cpu == 0 && cpustop_restartfunc != NULL)
cpustop_restartfunc();
return 0;
}
#endif /* KDB_STOP_NMI */
/*
* This is called once the rest of the system is up and running and we're
* ready to let the AP's out of the pen.

8
sys/i386/i386/trap.c
View file

@ -183,6 +183,14 @@ trap(frame)
PCPU_LAZY_INC(cnt.v_trap);
type = frame.tf_trapno;
#ifdef KDB_STOP_NMI
/* Handler for NMI IPIs used for debugging */
if (type == T_NMI) {
if (ipi_nmi_handler() == 0)
goto out;
}
#endif /* KDB_STOP_NMI */
#ifdef KDB
if (kdb_active) {
kdb_reenter();

5
sys/i386/include/smp.h
View file

@ -79,6 +79,11 @@ void smp_masked_invlpg_range(u_int mask, vm_offset_t startva,
void smp_invltlb(void);
void smp_masked_invltlb(u_int mask);
#ifdef KDB_STOP_NMI
int ipi_nmi_handler(void);
void ipi_nmi_selected(u_int32_t cpus);
#endif
#endif /* !LOCORE */
#endif /* SMP */

50
sys/kern/subr_kdb.c
View file

@ -40,6 +40,18 @@ __FBSDID("$FreeBSD$");
#include <machine/kdb.h>
#include <machine/pcb.h>
#ifdef KDB_STOP_NMI
#include <machine/smp.h>
#endif
/*
* KDB_STOP_NMI requires SMP to pick up the right dependencies
* (And isn't useful on UP anyway)
*/
#if defined(KDB_STOP_NMI) && !defined(SMP)
#error "options KDB_STOP_NMI" requires "options SMP"
#endif
int kdb_active = 0;
void *kdb_jmpbufp = NULL;
struct kdb_dbbe *kdb_dbbe = NULL;
@ -77,6 +89,19 @@ static int kdb_stop_cpus = 1;
SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLTYPE_INT | CTLFLAG_RW,
&kdb_stop_cpus, 0, "");
TUNABLE_INT("debug.kdb.stop_cpus", &kdb_stop_cpus);
#ifdef KDB_STOP_NMI
/*
* Provide an alternate method of stopping other CPUs. If another CPU has
* disabled interrupts the conventional STOP IPI will be blocked. This
* NMI-based stop should get through in that case.
*/
static int kdb_stop_cpus_with_nmi = 0;
SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus_with_nmi, CTLTYPE_INT | CTLFLAG_RW,
&kdb_stop_cpus_with_nmi, 0, "");
TUNABLE_INT("debug.kdb.stop_cpus_with_nmi", &kdb_stop_cpus_with_nmi);
#endif /* KDB_STOP_NMI */
#endif
static int
@ -308,9 +333,27 @@ kdb_reenter(void)
struct pcb *
kdb_thr_ctx(struct thread *thr)
#ifdef KDB_STOP_NMI
{
u_int cpuid;
struct pcpu *pc;
if (thr == curthread)
return &kdb_pcb;
SLIST_FOREACH(pc, &cpuhead, pc_allcpu) {
cpuid = pc->pc_cpuid;
if (pc->pc_curthread == thr && (atomic_load_acq_int(&stopped_cpus) & (1 << cpuid)))
return &stoppcbs[cpuid];
}
return thr->td_pcb;
}
#else
{
return ((thr == curthread) ? &kdb_pcb : thr->td_pcb);
}
#endif /* KDB_STOP_NMI */
struct thread *
kdb_thr_first(void)
@ -407,7 +450,14 @@ kdb_trap(int type, int code, struct trapframe *tf)
#ifdef SMP
if ((did_stop_cpus = kdb_stop_cpus) != 0)
{
#ifdef KDB_STOP_NMI
if(kdb_stop_cpus_with_nmi)
stop_cpus_nmi(PCPU_GET(other_cpus));
else
#endif /* KDB_STOP_NMI */
stop_cpus(PCPU_GET(other_cpus));
}
#endif
kdb_frame = tf;

29
sys/kern/subr_smp.c
View file

@ -254,6 +254,35 @@ stop_cpus(cpumask_t map)
return 1;
}
#ifdef KDB_STOP_NMI
int
stop_cpus_nmi(cpumask_t map)
{
int i;
if (!smp_started)
return 0;
CTR1(KTR_SMP, "stop_cpus(%x)", map);
/* send the stop IPI to all CPUs in map */
ipi_nmi_selected(map);
i = 0;
while ((atomic_load_acq_int(&stopped_cpus) & map) != map) {
/* spin */
i++;
#ifdef DIAGNOSTIC
if (i == 100000) {
printf("timeout stopping cpus\n");
break;
}
#endif
}
return 1;
}
#endif /* KDB_STOP_NMI */
/*
* Called by a CPU to restart stopped CPUs.

4
sys/sys/smp.h
View file

@ -101,6 +101,10 @@ int restart_cpus(cpumask_t);
int stop_cpus(cpumask_t);
void smp_rendezvous_action(void);
extern struct mtx smp_ipi_mtx;
#ifdef KDB_STOP_NMI
int stop_cpus_nmi(cpumask_t);
#endif
#endif /* SMP */
void smp_rendezvous(void (*)(void *),
void (*)(void *),