The patch titled
dynamic_debug: use a single printk() to emit messages
has been added to the -mm tree. Its filename is
dynamic_debug-use-a-single-printk-to-emit-messages.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: dynamic_debug: use a single printk() to emit messages
From: Jason Baron <jbaron@xxxxxxxxxx>
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.
Signed-off-by: Jason Baron <jbaron@xxxxxxxxxx>
Cc: Greg KH <greg@xxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/dynamic_debug.c | 72 +++++++++++++++++++-----------------------
1 file changed, 33 insertions(+), 39 deletions(-)
diff -puN lib/dynamic_debug.c~dynamic_debug-use-a-single-printk-to-emit-messages lib/dynamic_debug.c
--- a/lib/dynamic_debug.c~dynamic_debug-use-a-single-printk-to-emit-messages
+++ a/lib/dynamic_debug.c
@@ -422,52 +422,52 @@ static int ddebug_exec_query(char *query
return 0;
}
-static int dynamic_emit_prefix(const struct _ddebug *descriptor)
+#define PREFIX_SIZE 64
+#define LEFT(wrote) ((PREFIX_SIZE - wrote) > 0) ? (PREFIX_SIZE - wrote) : 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, LEFT(pos), "%s", KERN_DEBUG);
+ if (desc->flags & _DPRINTK_FLAGS_INCL_TID) {
if (in_interrupt())
- snprintf(tid, sizeof(tid), "%s", "<intr> ");
+ pos += snprintf(buf + pos, LEFT(pos), "%s ",
+ "<intr>");
else
- snprintf(tid, sizeof(tid), "[%d] ",
- task_pid_vnr(current));
- } else {
- tid[0] = 0;
+ pos += snprintf(buf + pos, LEFT(pos), "[%d] ",
+ task_pid_vnr(current));
}
+ pos_after_tid = pos;
+ if (desc->flags & _DPRINTK_FLAGS_INCL_MODNAME)
+ pos += snprintf(buf + pos, LEFT(pos), "%s:", desc->modname);
+ if (desc->flags & _DPRINTK_FLAGS_INCL_FUNCNAME)
+ pos += snprintf(buf + pos, LEFT(pos), "%s:", desc->function);
+ if (desc->flags & _DPRINTK_FLAGS_INCL_LINENO)
+ pos += snprintf(buf + pos, LEFT(pos), "%d:", desc->lineno);
+ if (pos - pos_after_tid)
+ pos += snprintf(buf + pos, LEFT(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 +480,15 @@ int __dynamic_dev_dbg(struct _ddebug *de
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 +501,15 @@ int __dynamic_netdev_dbg(struct _ddebug
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;
_
Patches currently in -mm which might be from jbaron@xxxxxxxxxx are
linux-next.patch
dynamic_debug-consolidate-repetitive-struct-_ddebug-descriptor-definitions.patch
dynamic_debug-consolidate-repetitive-struct-_ddebug-descriptor-definitions-fix.patch
dynamic_debug-remove-num_enabled-accounting.patch
dynamic_debug-use-a-single-printk-to-emit-messages.patch
dynamic_debug-use-a-single-printk-to-emit-messages-fix.patch
dynamic_debug-fix-undefined-reference-to-__netdev_printk.patch
epoll-limit-paths.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
