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Add a new sysctl, debug.kdb.stop_cpus, which controls whether or not we

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attempt to IPI other cpus when entering the debugger in order to stop
them while in the debugger.  The default remains to issue the stop;
however, that can result in a hang if another cpu has interrupts disabled
and is spinning, since the IPI won't be received and the KDB will wait
indefinitely.  We probably need to add a timeout, but this is a useful
stopgap in the mean time.

Reviewed by:	marcel
This commit is contained in:
Robert Watson 2004-08-15 02:06:27 +00:00
parent adb03c6788
commit d8939d82cb
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=133737
1 changed files with 19 additions and 2 deletions
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21
sys/kern/subr_kdb.c
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@ -66,6 +66,18 @@ SYSCTL_PROC(_debug_kdb, OID_AUTO, current, CTLTYPE_STRING | CTLFLAG_RW, 0, 0,
SYSCTL_PROC(_debug_kdb, OID_AUTO, enter, CTLTYPE_INT | CTLFLAG_RW, 0, 0,
kdb_sysctl_enter, "I", "set to enter the debugger");
/*
* Flag indicating whether or not to IPI the other CPUs to stop them on
* entering the debugger. Sometimes, this will result in a deadlock as
* stop_cpus() waits for the other cpus to stop, so we allow it to be
* disabled.
*/
#ifdef SMP
static int kdb_stop_cpus = 1;
SYSCTL_INT(_debug_kdb, OID_AUTO, stop_cpus, CTLTYPE_INT | CTLFLAG_RW,
&kdb_stop_cpus, 0, "");
#endif
static int
kdb_sysctl_available(SYSCTL_HANDLER_ARGS)
{
@ -374,6 +386,9 @@ kdb_thr_select(struct thread *thr)
int
kdb_trap(int type, int code, struct trapframe *tf)
{
#ifdef SMP
int did_stop_cpus;
#endif
int handled;
if (kdb_dbbe == NULL || kdb_dbbe->dbbe_trap == NULL)
@ -392,7 +407,8 @@ kdb_trap(int type, int code, struct trapframe *tf)
kdb_thr_select(curthread);
#ifdef SMP
stop_cpus(PCPU_GET(other_cpus));
if ((did_stop_cpus = kdb_stop_cpus) != 0)
stop_cpus(PCPU_GET(other_cpus));
#endif
/* Let MD code do its thing first... */
@ -401,7 +417,8 @@ kdb_trap(int type, int code, struct trapframe *tf)
handled = kdb_dbbe->dbbe_trap(type, code);
#ifdef SMP
restart_cpus(stopped_cpus);
if (did_stop_cpus)
restart_cpus(stopped_cpus);
#endif
kdb_active--;