Commit 431625da authored by Jason Baron's avatar Jason Baron Committed by Greg Kroah-Hartman
Browse files

dynamic_debug: use a single printk() to emit messages 



We were using KERN_CONT to combine messages with their prefix.  However,
KERN_CONT is not smp safe, in the sense that it can interleave messages.
This interleaving can result in printks coming out at the wrong loglevel.
With the high frequency of printks that dynamic debug can produce this is
not desirable.

So make dynamic_emit_prefix() fill a char buf[64] instead of doing a
printk directly.  If we enable printing out of function, module, line, or
pid info, they are placed in this 64 byte buffer.  In my testing 64 bytes
was enough size to fulfill all requests.  Even if it's not, we can match
up the printk itself to see where it's from, so to me this is no big deal.

[akpm@linux-foundation.org: convert dangerous macro to C]
Signed-off-by: default avatarJason Baron <jbaron@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarAndrew Morton <akpm@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent bd22c01e

lib/dynamic_debug.c

+41 −39
Original line number Diff line number Diff line
@@ -422,52 +422,60 @@ static int ddebug_exec_query(char *query_string) 
	return 0;

}



static int dynamic_emit_prefix(const struct _ddebug *descriptor)

#define PREFIX_SIZE 64



static int remaining(int wrote)

{

	if (PREFIX_SIZE - wrote > 0)

		return PREFIX_SIZE - wrote;

	return 0;

}



static char *dynamic_emit_prefix(const struct _ddebug *desc, char *buf)

{

	char tid[sizeof(int) + sizeof(int)/2 + 4];

	char lineno[sizeof(int) + sizeof(int)/2];

	int pos_after_tid;

	int pos = 0;



	if (descriptor->flags & _DPRINTK_FLAGS_INCL_TID) {

	pos += snprintf(buf + pos, remaining(pos), "%s", KERN_DEBUG);

	if (desc->flags & _DPRINTK_FLAGS_INCL_TID) {

		if (in_interrupt())

			snprintf(tid, sizeof(tid), "%s", "<intr> ");

			pos += snprintf(buf + pos, remaining(pos), "%s ",

						"<intr>");

		else

			snprintf(tid, sizeof(tid), "[%d] ",

			pos += snprintf(buf + pos, remaining(pos), "[%d] ",

						task_pid_vnr(current));

	} else {

		tid[0] = 0;

	}

	pos_after_tid = pos;

	if (desc->flags & _DPRINTK_FLAGS_INCL_MODNAME)

		pos += snprintf(buf + pos, remaining(pos), "%s:",

					desc->modname);

	if (desc->flags & _DPRINTK_FLAGS_INCL_FUNCNAME)

		pos += snprintf(buf + pos, remaining(pos), "%s:",

					desc->function);

	if (desc->flags & _DPRINTK_FLAGS_INCL_LINENO)

		pos += snprintf(buf + pos, remaining(pos), "%d:", desc->lineno);

	if (pos - pos_after_tid)

		pos += snprintf(buf + pos, remaining(pos), " ");

	if (pos >= PREFIX_SIZE)

		buf[PREFIX_SIZE - 1] = '\0';



	if (descriptor->flags & _DPRINTK_FLAGS_INCL_LINENO)

		snprintf(lineno, sizeof(lineno), "%d", descriptor->lineno);

	else

		lineno[0] = 0;



	return printk(KERN_DEBUG "%s%s%s%s%s%s",

		      tid,

		      (descriptor->flags & _DPRINTK_FLAGS_INCL_MODNAME) ?

		      descriptor->modname : "",

		      (descriptor->flags & _DPRINTK_FLAGS_INCL_MODNAME) ?

		      ":" : "",

		      (descriptor->flags & _DPRINTK_FLAGS_INCL_FUNCNAME) ?

		      descriptor->function : "",

		      (descriptor->flags & _DPRINTK_FLAGS_INCL_FUNCNAME) ?

		      ":" : "",

		      lineno);

	return buf;

}



int __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...)

{

	va_list args;

	int res;

	struct va_format vaf;

	char buf[PREFIX_SIZE];



	BUG_ON(!descriptor);

	BUG_ON(!fmt);



	va_start(args, fmt);



	res = dynamic_emit_prefix(descriptor);

	res += vprintk(fmt, args);



	vaf.fmt = fmt;

	vaf.va = &args;

	res = printk("%s%pV", dynamic_emit_prefix(descriptor, buf), &vaf);

	va_end(args);



	return res;
@@ -480,18 +488,15 @@ int __dynamic_dev_dbg(struct _ddebug *descriptor, 
	struct va_format vaf;

	va_list args;

	int res;

	char buf[PREFIX_SIZE];



	BUG_ON(!descriptor);

	BUG_ON(!fmt);



	va_start(args, fmt);



	vaf.fmt = fmt;

	vaf.va = &args;



	res = dynamic_emit_prefix(descriptor);

	res += __dev_printk(KERN_CONT, dev, &vaf);



	res = __dev_printk(dynamic_emit_prefix(descriptor, buf), dev, &vaf);

	va_end(args);



	return res;
@@ -504,18 +509,15 @@ int __dynamic_netdev_dbg(struct _ddebug *descriptor, 
	struct va_format vaf;

	va_list args;

	int res;

	char buf[PREFIX_SIZE];



	BUG_ON(!descriptor);

	BUG_ON(!fmt);



	va_start(args, fmt);



	vaf.fmt = fmt;

	vaf.va = &args;



	res = dynamic_emit_prefix(descriptor);

	res += __netdev_printk(KERN_CONT, dev, &vaf);



	res = __netdev_printk(dynamic_emit_prefix(descriptor, buf), dev, &vaf);

	va_end(args);



	return res;

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