Hi,
When doing usb debugging with a lot of kernel printfs, the dmesg
buffer can overflow easily. It is annoying that you don't notice
this. Then it is hard to correlate the messages.
So to make clear what happens, I would like to write such a message
to syslogd:
Jun 22 21:58:16 t430s /bsd: usbd_start_next: pipe=0xffff8000003cf
Jun 22 21:58:16 t430s /bsd: klog: dropped 75602 bytes, message buffer full
Jun 22 21:58:16 t430s /bsd: b_transfer_complete: repeat=0 new head=0x0
This also gets me closer to my goal of reliable logging.
Do we want this feature?
bluhm
Index: kern/subr_log.c
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/kern/subr_log.c,v
retrieving revision 1.46
diff -u -p -r1.46 subr_log.c
--- kern/subr_log.c 8 Jun 2016 11:11:47 -0000 1.46
+++ kern/subr_log.c 22 Jun 2016 20:09:08 -0000
@@ -155,6 +155,7 @@ msgbuf_putchar(struct msgbuf *mbp, const
if (mbp->msg_bufr == mbp->msg_bufx) {
if (++mbp->msg_bufr >= mbp->msg_bufs)
mbp->msg_bufr = 0;
+ mbp->msg_bufd++;
}
splx(s);
}
@@ -200,6 +201,21 @@ logread(dev_t dev, struct uio *uio, int
goto out;
}
logsoftc.sc_state &= ~LOG_RDWAIT;
+
+#ifndef SMALL_KERNEL
+ if (mbp->msg_bufd > 0) {
+ char buf[64];
+
+ l = snprintf(buf, sizeof(buf),
+ "<%d>klog: dropped %ld byte%s, message buffer full\n",
+ LOG_KERN|LOG_WARNING, mbp->msg_bufd,
+ mbp->msg_bufd == 1 ? "" : "s");
+ error = uiomove(buf, ulmin(l, sizeof(buf) - 1), uio);
+ if (error)
+ goto out;
+ mbp->msg_bufd = 0;
+ }
+#endif
while (uio->uio_resid > 0) {
if (mbp->msg_bufx >= mbp->msg_bufr)
Index: sys/msgbuf.h
===================================================================
RCS file: /data/mirror/openbsd/cvs/src/sys/sys/msgbuf.h,v
retrieving revision 1.10
diff -u -p -r1.10 msgbuf.h
--- sys/msgbuf.h 13 Jan 2015 18:51:27 -0000 1.10
+++ sys/msgbuf.h 22 Jun 2016 19:45:10 -0000
@@ -39,6 +39,7 @@ struct msgbuf {
long msg_bufr; /* read pointer */
long msg_bufs; /* real msg_bufc size (bytes) */
long msg_bufl; /* # chars, <= msg_bufs */
+ long msg_bufd; /* number of dropped bytes */
char msg_bufc[1]; /* buffer */
};
#ifdef _KERNEL
