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Subject[PATCH 1/5] dev_dbg/dynamic_debug: Update to use printk_emit, optimize stack
From
Date
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>

---
drivers/base/core.c | 64 +++++++++++++++++++++++++----------------------
include/linux/device.h | 8 +++---
lib/dynamic_debug.c | 39 +++++++++++++++++++++-------
3 files changed, 67 insertions(+), 44 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 5e6e00b..d46b635 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -1861,26 +1861,19 @@ 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=:
@@ -1896,32 +1889,41 @@ 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, ...)
@@ -1936,6 +1938,7 @@ int dev_printk(const char *level, const struct device *dev,
vaf.va = &args;

r = __dev_printk(level, dev, &vaf);
+
va_end(args);

return r;
@@ -1955,6 +1958,7 @@ 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 52a5f15..4800d73 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -891,12 +891,12 @@ 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 7ca29a0..29ff2e4 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;
--
1.7.8.111.gad25c.dirty



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