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dynamic_debug: use a single printk() to emit messages

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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: Jason Baron <jbaron@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Jason Baron 2011-10-04 14:13:19 -07:00 committed by Greg Kroah-Hartman
parent bd22c01e84
commit 431625dac1
1 changed files with 41 additions and 39 deletions
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80
lib/dynamic_debug.c
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@ -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)
{
char tid[sizeof(int) + sizeof(int)/2 + 4];
char lineno[sizeof(int) + sizeof(int)/2];
if (PREFIX_SIZE - wrote > 0)
return PREFIX_SIZE - wrote;
return 0;
}
if (descriptor->flags & _DPRINTK_FLAGS_INCL_TID) {
static char *dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
{
int pos_after_tid;
int pos = 0;
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] ",
task_pid_vnr(current));
} else {
tid[0] = 0;
pos += snprintf(buf + pos, remaining(pos), "[%d] ",
task_pid_vnr(current));
}
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;