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Add a new userland-visible ktrace flag KTR_DROP and an internal ktrace flag

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KTRFAC_DROP to track instances when ktrace events are dropped due to the
request pool being exhausted.  When a thread tries to post a ktrace event
and is unable to due to no available ktrace request objects, it sets
KTRFAC_DROP in its process' p_traceflag field.  The next trace event to
successfully post from that process will set the KTR_DROP flag in the
header of the request going out and clear KTRFAC_DROP.

The KTR_DROP flag is the high bit in the type field of the ktr_header
structure.  Older kdump binaries will simply complain about an unknown type
when seeing an entry with KTR_DROP set.  Note that KTR_DROP being set on a
record in a ktrace file does not tell you anything except that at least one
event from this process was dropped prior to this event.  The user has no
way of knowing what types of events were dropped nor how many were dropped.

Requested by:	phk
This commit is contained in:
John Baldwin 2003-03-13 18:31:15 +00:00
parent a5881ea55a
commit 75768576cc
2 changed files with 13 additions and 1 deletions
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7
sys/kern/kern_ktrace.c
View File

@ -226,6 +226,10 @@ ktr_getrequest(int type)
if (req != NULL) {
STAILQ_REMOVE_HEAD(&ktr_free, ktr_list);
req->ktr_header.ktr_type = type;
if (p->p_traceflag & KTRFAC_DROP) {
req->ktr_header.ktr_type |= KTR_DROP;
p->p_traceflag &= ~KTRFAC_DROP;
}
KASSERT(p->p_tracevp != NULL, ("ktrace: no trace vnode"));
KASSERT(p->p_tracecred != NULL, ("ktrace: no trace cred"));
req->ktr_vp = p->p_tracevp;
@ -238,6 +242,7 @@ ktr_getrequest(int type)
req->ktr_header.ktr_buffer = NULL;
req->ktr_header.ktr_len = 0;
} else {
p->p_traceflag |= KTRFAC_DROP;
pm = print_message;
print_message = 0;
mtx_unlock(&ktrace_mtx);
@ -762,7 +767,7 @@ ktr_writerequest(struct ktr_request *req)
if (vp == NULL)
return;
kth = &req->ktr_header;
datalen = data_lengths[kth->ktr_type];
datalen = data_lengths[(ushort)kth->ktr_type & ~KTR_DROP];
buflen = kth->ktr_len;
cred = req->ktr_cred;
td = curthread;

7
sys/sys/ktrace.h
View File

@ -144,6 +144,12 @@ struct ktr_csw {
#define KTR_USER_MAXLEN 2048 /* maximum length of passed data */
#define KTR_USER 7
/*
* KTR_DROP - If this bit is set in ktr_type, then at least one event
* between the previous record and this record was dropped.
*/
#define KTR_DROP 0x8000
/*
* kernel trace points (in p_traceflag)
*/
@ -160,6 +166,7 @@ struct ktr_csw {
*/
#define KTRFAC_ROOT 0x80000000 /* root set this trace */
#define KTRFAC_INHERIT 0x40000000 /* pass trace flags to children */
#define KTRFAC_DROP 0x20000000 /* last event was dropped */
#ifdef _KERNEL
extern struct mtx ktrace_mtx;