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Add kernel option KSTACK_USAGE_PROF to sample the stack depth on

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interrupts and report the largest value seen as sysctl
debug.max_kstack_used.  Useful to estimate how close the kernel stack
size is to overflow.

In collaboration with:	Larry Baird <lab@gta.com>
Sponsored by:	The FreeBSD Foundation (kib)
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2014-10-04 18:38:14 +00:00
parent 539c9eef12
commit b76278407d
5 changed files with 58 additions and 0 deletions
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1
sys/conf/NOTES
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@ -2958,6 +2958,7 @@ options SC_RENDER_DEBUG # syscons rendering debugging
options VFS_BIO_DEBUG # VFS buffer I/O debugging
options KSTACK_MAX_PAGES=32 # Maximum pages to give the kernel stack
options KSTACK_USAGE_PROF
# Adaptec Array Controller driver options
options AAC_DEBUG # Debugging levels:

1
sys/conf/options
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@ -136,6 +136,7 @@ KDTRACE_FRAME opt_kdtrace.h
KN_HASHSIZE opt_kqueue.h
KSTACK_MAX_PAGES
KSTACK_PAGES
KSTACK_USAGE_PROF
KTRACE
KTRACE_REQUEST_POOL opt_ktrace.h
LIBICONV

5
sys/kern/kern_intr.c
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@ -28,6 +28,7 @@
__FBSDID("$FreeBSD$");
#include "opt_ddb.h"
#include "opt_kstack_usage_prof.h"
#include <sys/param.h>
#include <sys/bus.h>
@ -1396,6 +1397,10 @@ intr_event_handle(struct intr_event *ie, struct trapframe *frame)
td = curthread;
#ifdef KSTACK_USAGE_PROF
intr_prof_stack_use(td, frame);
#endif
/* An interrupt with no event or handlers is a stray interrupt. */
if (ie == NULL || TAILQ_EMPTY(&ie->ie_handlers))
return (EINVAL);

2
sys/sys/systm.h
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@ -443,4 +443,6 @@ bitcount16(uint32_t x)
return (x);
}
void intr_prof_stack_use(struct thread *td, struct trapframe *frame);
#endif /* !_SYS_SYSTM_H_ */

49
sys/vm/vm_glue.c
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@ -62,6 +62,7 @@ __FBSDID("$FreeBSD$");
#include "opt_vm.h"
#include "opt_kstack_pages.h"
#include "opt_kstack_max_pages.h"
#include "opt_kstack_usage_prof.h"
#include <sys/param.h>
#include <sys/systm.h>
@ -98,6 +99,8 @@ __FBSDID("$FreeBSD$");
#include <vm/vm_pager.h>
#include <vm/swap_pager.h>
#include <machine/cpu.h>
#ifndef NO_SWAPPING
static int swapout(struct proc *);
static void swapclear(struct proc *);
@ -486,6 +489,52 @@ kstack_cache_init(void *nulll)
SYSINIT(vm_kstacks, SI_SUB_KTHREAD_INIT, SI_ORDER_ANY, kstack_cache_init, NULL);
#ifdef KSTACK_USAGE_PROF
/*
* Track maximum stack used by a thread in kernel.
*/
static int max_kstack_used;
SYSCTL_INT(_debug, OID_AUTO, max_kstack_used, CTLFLAG_RD,
&max_kstack_used, 0,
"Maxiumum stack depth used by a thread in kernel");
void
intr_prof_stack_use(struct thread *td, struct trapframe *frame)
{
vm_offset_t stack_top;
vm_offset_t current;
int used, prev_used;
/*
* Testing for interrupted kernel mode isn't strictly
* needed. It optimizes the execution, since interrupts from
* usermode will have only the trap frame on the stack.
*/
if (TRAPF_USERMODE(frame))
return;
stack_top = td->td_kstack + td->td_kstack_pages * PAGE_SIZE;
current = (vm_offset_t)(uintptr_t)&stack_top;
/*
* Try to detect if interrupt is using kernel thread stack.
* Hardware could use a dedicated stack for interrupt handling.
*/
if (stack_top <= current || current < td->td_kstack)
return;
used = stack_top - current;
for (;;) {
prev_used = max_kstack_used;
if (prev_used >= used)
break;
if (atomic_cmpset_int(&max_kstack_used, prev_used, used))
break;
}
}
#endif /* KSTACK_USAGE_PROF */
#ifndef NO_SWAPPING
/*
* Allow a thread's kernel stack to be paged out.