dev_dbg/dynamic_debug: Update to use printk_emit, optimize stack

commit c4e00daaa9
("driver-core: extend dev_printk() to pass structured data")
changed __dev_printk and broke dynamic-debug's ability to control the
dynamic prefix of dev_dbg(dev,..).

commit af7f2158fd
("drivers-core: make structured logging play nice with dynamic-debug")
made a minimal correction.

The current dynamic debug code uses up to 3 recursion levels via %pV.
This can consume quite a bit of stack.  Directly call printk_emit to
reduce the recursion depth.

These changes include:

dev_dbg:
o Create and use function create_syslog_header to format the syslog
  header for printk_emit uses.
o Call create_syslog_header and neaten __dev_printk
o Make __dev_printk static not global
o Remove include header declaration of __dev_printk
o Remove now unused EXPORT_SYMBOL() of __dev_printk
o Whitespace neatening

dynamic_dev_dbg:
o Remove KERN_DEBUG from dynamic_emit_prefix
o Call create_syslog_header and printk_emit
o Whitespace neatening

Signed-off-by: Joe Perches <joe@perches.com>
Acked-by: David S. Miller <davem@davemloft.net>
Tested-by: Jim Cromie <jim.cromie@gmail.com>
Acked-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 67 insertions, 44 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 91478bd35418..d325b9dab3ff 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1865,26 +1865,19 @@ void device_shutdown(void)
  */
 
 #ifdef CONFIG_PRINTK
-int __dev_printk(const char *level, const struct device *dev,
-                 struct va_format *vaf)
+int create_syslog_header(const struct device *dev, char *hdr, size_t hdrlen)
 {
-        char dict[128];
-        const char *level_extra = "";
-        size_t dictlen = 0;
         const char *subsys;
-
-        if (!dev)
-                return printk("%s(NULL device *): %pV", level, vaf);
+        size_t pos = 0;
 
         if (dev->class)
                 subsys = dev->class->name;
         else if (dev->bus)
                 subsys = dev->bus->name;
         else
-                goto skip;
+                return 0;
 
-        dictlen += snprintf(dict + dictlen, sizeof(dict) - dictlen,
-                            "SUBSYSTEM=%s", subsys);
+        pos += snprintf(hdr + pos, hdrlen - pos, "SUBSYSTEM=%s", subsys);
 
         /*
          * Add device identifier DEVICE=:
@@ -1900,32 +1893,41 @@ int __dev_printk(const char *level, const struct device *dev,
                         c = 'b';
                 else
                         c = 'c';
-                dictlen++;
-                dictlen += snprintf(dict + dictlen, sizeof(dict) - dictlen,
-                                   "DEVICE=%c%u:%u",
-                                   c, MAJOR(dev->devt), MINOR(dev->devt));
+                pos++;
+                pos += snprintf(hdr + pos, hdrlen - pos,
+                                "DEVICE=%c%u:%u",
+                                c, MAJOR(dev->devt), MINOR(dev->devt));
         } else if (strcmp(subsys, "net") == 0) {
                 struct net_device *net = to_net_dev(dev);
 
-                dictlen++;
-                dictlen += snprintf(dict + dictlen, sizeof(dict) - dictlen,
-                                    "DEVICE=n%u", net->ifindex);
+                pos++;
+                pos += snprintf(hdr + pos, hdrlen - pos,
+                                "DEVICE=n%u", net->ifindex);
         } else {
-                dictlen++;
-                dictlen += snprintf(dict + dictlen, sizeof(dict) - dictlen,
-                                    "DEVICE=+%s:%s", subsys, dev_name(dev));
+                pos++;
+                pos += snprintf(hdr + pos, hdrlen - pos,
+                                "DEVICE=+%s:%s", subsys, dev_name(dev));
         }
-skip:
-        if (level[2])
-                level_extra = &level[2]; /* skip past KERN_SOH "L" */
 
-        return printk_emit(0, level[1] - '0',
-                           dictlen ? dict : NULL, dictlen,
-                           "%s %s: %s%pV",
-                           dev_driver_string(dev), dev_name(dev),
-                           level_extra, vaf);
+        return pos;
+}
+EXPORT_SYMBOL(create_syslog_header);
+
+static int __dev_printk(const char *level, const struct device *dev,
+                        struct va_format *vaf)
+{
+        char hdr[128];
+        size_t hdrlen;
+
+        if (!dev)
+                return printk("%s(NULL device *): %pV", level, vaf);
+
+        hdrlen = create_syslog_header(dev, hdr, sizeof(hdr));
+
+        return printk_emit(0, level[1] - '0', hdrlen ? hdr : NULL, hdrlen,
+                           "%s %s: %pV",
+                           dev_driver_string(dev), dev_name(dev), vaf);
 }
-EXPORT_SYMBOL(__dev_printk);
 
 int dev_printk(const char *level, const struct device *dev,
                const char *fmt, ...)
@@ -1940,6 +1942,7 @@ int dev_printk(const char *level, const struct device *dev,
         vaf.va = &args;
 
         r = __dev_printk(level, dev, &vaf);
+
         va_end(args);
 
         return r;
@@ -1959,6 +1962,7 @@ int func(const struct device *dev, const char *fmt, ...)	\
         vaf.va = &args;                                         \
                                                                 \
         r = __dev_printk(kern_level, dev, &vaf);                \
+                                                                \
         va_end(args);                                           \
                                                                 \
         return r;                                               \
diff --git a/include/linux/device.h b/include/linux/device.h
index 378a27c1d1af..a1443b48ed4b 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -895,12 +895,12 @@ extern const char *dev_driver_string(const struct device *dev);
 
 #ifdef CONFIG_PRINTK
 
-extern int __dev_printk(const char *level, const struct device *dev,
-                        struct va_format *vaf);
+extern int create_syslog_header(const struct device *dev,
+                                char *hdr, size_t hdrlen);
+
 extern __printf(3, 4)
 int dev_printk(const char *level, const struct device *dev,
-               const char *fmt, ...)
-        ;
+               const char *fmt, ...);
 extern __printf(2, 3)
 int dev_emerg(const struct device *dev, const char *fmt, ...);
 extern __printf(2, 3)
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 7ca29a0a3019..29ff2e4cfb75 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -521,25 +521,25 @@ 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);
+        *buf = '\0';
+
         if (desc->flags & _DPRINTK_FLAGS_INCL_TID) {
                 if (in_interrupt())
-                        pos += snprintf(buf + pos, remaining(pos), "%s ",
-                                                "<intr>");
+                        pos += snprintf(buf + pos, remaining(pos), "<intr> ");
                 else
                         pos += snprintf(buf + pos, remaining(pos), "[%d] ",
-                                                task_pid_vnr(current));
+                                        task_pid_vnr(current));
         }
         pos_after_tid = pos;
         if (desc->flags & _DPRINTK_FLAGS_INCL_MODNAME)
                 pos += snprintf(buf + pos, remaining(pos), "%s:",
-                                        desc->modname);
+                                desc->modname);
         if (desc->flags & _DPRINTK_FLAGS_INCL_FUNCNAME)
                 pos += snprintf(buf + pos, remaining(pos), "%s:",
-                                        desc->function);
+                                desc->function);
         if (desc->flags & _DPRINTK_FLAGS_INCL_LINENO)
                 pos += snprintf(buf + pos, remaining(pos), "%d:",
-                                        desc->lineno);
+                                desc->lineno);
         if (pos - pos_after_tid)
                 pos += snprintf(buf + pos, remaining(pos), " ");
         if (pos >= PREFIX_SIZE)
@@ -559,9 +559,13 @@ int __dynamic_pr_debug(struct _ddebug *descriptor, const char *fmt, ...)
         BUG_ON(!fmt);
 
         va_start(args, fmt);
+
         vaf.fmt = fmt;
         vaf.va = &args;
-        res = printk("%s%pV", dynamic_emit_prefix(descriptor, buf), &vaf);
+
+        res = printk(KERN_DEBUG "%s%pV",
+                     dynamic_emit_prefix(descriptor, buf), &vaf);
+
         va_end(args);
 
         return res;
@@ -574,15 +578,30 @@ 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 = __dev_printk(dynamic_emit_prefix(descriptor, buf), dev, &vaf);
+
+        if (!dev) {
+                res = printk(KERN_DEBUG "(NULL device *): %pV", &vaf);
+        } else {
+                char buf[PREFIX_SIZE];
+                char dict[128];
+                size_t dictlen;
+
+                dictlen = create_syslog_header(dev, dict, sizeof(dict));
+
+                res = printk_emit(0, 7, dictlen ? dict : NULL, dictlen,
+                                  "%s%s %s: %pV",
+                                  dynamic_emit_prefix(descriptor, buf),
+                                  dev_driver_string(dev), dev_name(dev), &vaf);
+        }
+
         va_end(args);
 
         return res;