Messages in this thread | | | Date | Tue, 1 Apr 2008 14:47:44 -0700 | From | Randy Dunlap <> | Subject | Re: [patch 1/3] dynamic printk - core infrastructure |
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On Tue, 1 Apr 2008 15:49:51 -0400 Jason Baron wrote:
> > Add the ability to dynamically enable/disable pr_debug()/dev_dbg() in the > kernel. Yes, these calls could be converted to printk(KERN_DEBUG), but there > are enough to cause overhead. Additionally, the logs become difficult to read. > Here, one can turn on and off these messages per .c source file via: > > echo "add file.c" > /sys/kernel/debug/dynamic_printk/files > echo "remove file.c" > /sys/kernel/debug/dynamic_printk/files
Is <filename> the full path name or just the basename of the file? If just the basename, what happens for files that have duplicated basenames throughout the kernel tree?
> There is also a special 'all' value that turns on all the debugging messages. > > Signed-off-by: Jason Baron <jbaron@redhat.com> > --- > > include/linux/device.h | 12 ++ > include/linux/kernel.h | 11 ++ > lib/Kconfig.debug | 34 ++++++ > lib/Makefile | 2 > lib/dynamic_printk.c | 253 ++++++++++++++++++++++++++++++++++++++++++++++++ > 5 files changed, 312 insertions(+), 0 deletions(-) > create mode 100644 lib/dynamic_printk.c > > > diff --git a/include/linux/device.h b/include/linux/device.h > index db375be..b007f61 100644 > --- a/include/linux/device.h > +++ b/include/linux/device.h > @@ -587,6 +587,17 @@ extern const char *dev_driver_string(struct device *dev); > #define dev_info(dev, format, arg...) \ > dev_printk(KERN_INFO , dev , format , ## arg) > > +#ifdef CONFIG_DYNAMIC_PRINTK > +extern void dyanmic_printk(char *, char *, ...); > +DECLARE_IMV(char, dynamic_debug_on); > +#define dev_dbg(dev, format, arg...) \ > + do { \ > + if (unlikely(imv_read(dynamic_debug_on))) \ > + dynamic_printk(__FILE__, KERN_DEBUG "%s %s: " format, \ > + dev_driver_string(dev), (dev)->bus_id, \ > + ## arg); \ > + } while (0) > +#else > #ifdef DEBUG > #define dev_dbg(dev, format, arg...) \ > dev_printk(KERN_DEBUG , dev , format , ## arg) > @@ -597,6 +608,7 @@ dev_dbg(struct device *dev, const char *fmt, ...) > return 0; > } > #endif > +#endif > > #ifdef VERBOSE_DEBUG > #define dev_vdbg dev_dbg > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > index ff356b2..a311e87 100644 > --- a/include/linux/kernel.h > +++ b/include/linux/kernel.h > @@ -14,6 +14,7 @@ > #include <linux/compiler.h> > #include <linux/bitops.h> > #include <linux/log2.h> > +#include <linux/immediate.h> > #include <asm/byteorder.h> > #include <asm/bug.h> > > @@ -276,6 +277,15 @@ extern void print_hex_dump_bytes(const char *prefix_str, int prefix_type, > #define pr_info(fmt, arg...) \ > printk(KERN_INFO fmt, ##arg) > > +#ifdef CONFIG_DYNAMIC_PRINTK > +extern void dynamic_printk(char *, char *, ...); > +DECLARE_IMV(char, dynamic_debug_on); > +#define pr_debug(fmt, ...) \ > + do { \ > + if (unlikely(imv_read(dynamic_debug_on))) \ > + dynamic_printk(__FILE__, KERN_DEBUG fmt, ##__VA_ARGS__);\ > + } while (0)
That indentation should be more like it is in dev_dbg() above.
> +#else > #ifdef DEBUG > /* If you are writing a driver, please use dev_dbg instead */ > #define pr_debug(fmt, arg...) \ > @@ -286,6 +296,7 @@ static inline int __attribute__ ((format (printf, 1, 2))) pr_debug(const char * > return 0; > } > #endif > +#endif > > /* > * Display an IP address in readable format. > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 0d8a5a4..5454c0a 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -615,4 +615,38 @@ config PROVIDE_OHCI1394_DMA_INIT > > See Documentation/debugging-via-ohci1394.txt for more information. > > +config DYNAMIC_PRINTK > + bool "Enable dynamic printk() call support" > + default y
Why default yes?
> + depends on PRINTK > + help > + > + allows pr_debug() and dev_dbg() calls to be dynamically enabled based
Allows
> + upon their .c source file. Traditionally, these calls are only > + enabled if one set #define DEBUG and recompiled the kernel. This > + option obviates time consuming re-compiles.
time-consuming > + > + The impact of this compile option is a larger kerenl text size ~1%.
kernel
> + However, if CONFIG_IMMEDIATE is set, the run-time impact is > + negligible. Without CONFIG_IMMEDIATE set, a global variable is > + referenced for each pr_debug() and dev_dbg() calls. > + > + Usage: > + > + The printing of pr_debug() and dev_dbg() is controlled by the > + debugfs file, dynamic_printk/files. > + > + echo "add foo.c" > dynamic_printk/files > + echo "remove foo.c" > dynamic_printk/files > +
Does "cat dynamic_printk/files" do anything useful?
> + Also, a special "all" value will print all pr_debug() and dev_dbg() > + calls. ie:
I.e.:
> + > + echo "add all" > dynamic_printk/files > + echo "remove all" > dynamic_printk/files > + > + Finally, passing "dynamic_printk" at the command line enables all > + pr_debug() and dev_dbg() call to come out (same as "all"). This mode
calls
> + can be disabled via a "remove all" > +
Trailing whitespace (tab).
It looks like the use of "add/remove all" can only be done when nr_entries == 0 (no filename entries in the hash list). If that's the case, please document it.
> source "samples/Kconfig" > diff --git a/lib/dynamic_printk.c b/lib/dynamic_printk.c > new file mode 100644 > index 0000000..008496b > --- /dev/null > +++ b/lib/dynamic_printk.c > @@ -0,0 +1,253 @@ > +/* > + * lib/dynamic_printk.c > + * > + * make pr_debug()/dev_dbg() calls runtime configurable based upon their .c file > + * > + * Copyright (C) 2008 Red Hat, Inc., Jason Baron <jbaron@redhat.com> > + */ > + > +#include <linux/kernel.h> > +#include <linux/module.h> > +#include <linux/uaccess.h> > +#include <linux/seq_file.h> > +#include <linux/debugfs.h> > +#include <linux/fs.h> > +#include <linux/proc_fs.h> > +#include <linux/spinlock.h> > +#include <linux/hash.h> > + > +#define FILE_HASH_BITS 5 > +#define FILE_TABLE_SIZE (1 << FILE_HASH_BITS) > + > +DEFINE_IMV(char, dynamic_debug_on) = 0; > +EXPORT_IMV_SYMBOL_GPL(dynamic_debug_on); > + > +static int all; > +static struct hlist_head file_table[FILE_TABLE_SIZE] = > + { [0 ... FILE_TABLE_SIZE-1] = HLIST_HEAD_INIT }; > +static DECLARE_MUTEX(debug_list_mutex); > +static int nr_entries; > + > +struct debug_name { > + struct hlist_node hlist; > + char *name; > +}; > + > +static inline unsigned int name_hash(char *name) > +{ > + unsigned int hash = full_name_hash(name, strlen(name)); > + return (hash & ((1 << FILE_HASH_BITS) - 1)); > +} > + > +static struct debug_name *find_debug_file(char *file_name) > +{ > + int found = 0; > + struct hlist_head *head; > + struct hlist_node *node; > + struct debug_name *element; > + > + head = &file_table[name_hash(file_name)]; > + rcu_read_lock(); > + hlist_for_each_entry_rcu(element, node, head, hlist) { > + if (!strcmp(element->name, file_name)) { > + found = 1; > + break; > + } > + } > + rcu_read_unlock(); > + if (found) > + return element; > + return NULL; > +} > + > +static int add_debug_file(char *file_name) > +{ > + struct debug_name *new; > + > + if (find_debug_file(file_name)) > + return -EINVAL; > + new = kmalloc(sizeof(struct debug_name), GFP_KERNEL); > + if (!new) > + return -ENOMEM; > + INIT_HLIST_NODE(&new->hlist); > + new->name = file_name; > + hlist_add_head_rcu(&new->hlist, > + &file_table[name_hash(new->name)]); > + nr_entries++; > + return 0; > +} > + > +static int remove_debug_file(char *file_name) > +{ > + struct debug_name *element; > + > + element = find_debug_file(file_name); > + if (element == NULL) > + return -EINVAL; > + hlist_del_rcu(&element->hlist); > + synchronize_rcu(); > + kfree(element->name); > + kfree(element); > + nr_entries--; > + return 0; > +} > + > +void dynamic_printk(char *filename, char *fmt, ...) > +{ > + va_list args; > + > + va_start(args, fmt); > + if (all) > + vprintk(fmt, args); > + else { > + if (find_debug_file(filename)) > + vprintk(fmt, args); > + } > + va_end(args); > +} > +EXPORT_SYMBOL_GPL(dynamic_printk); > + > +static ssize_t pr_debug_write(struct file *file, const char __user *buf, > + size_t length, loff_t *ppos) > +{ > + char *buffer, *file_name, *s; > + int err; > + > + if (!buf || length > PAGE_SIZE || length < 0) > + return -EINVAL; > + > + buffer = (char *)__get_free_page(GFP_KERNEL); > + if (!buffer) > + return -ENOMEM; > + > + err = -EFAULT; > + if (copy_from_user(buffer, buf, length)) > + goto out; > + > + err = -EINVAL; > + if (length < PAGE_SIZE) > + buffer[length] = '\0'; > + else if (buffer[PAGE_SIZE-1]) > + goto out; > + > + err = -EINVAL; > + down(&debug_list_mutex); > + if (!strncmp("add all", buffer, 7)) { > + if (!all && (nr_entries == 0)) > + imv_set(dynamic_debug_on, 1); > + all = 1; > + err = 0; > + } else if (!strncmp("remove all", buffer, 10)) { > + if (all && (nr_entries == 0)) > + imv_set(dynamic_debug_on, 0); > + all = 0; > + err = 0; > + } else if (!strncmp("add ", buffer, 4)) { > + s = strstrip(buffer+4);
(buffer + 4);
> + file_name = kmalloc(strlen(s)+1, GFP_KERNEL);
strlen(s) + 1,
> + if (!file_name) { > + err = -ENOMEM; > + goto out_up; > + } > + file_name = strcpy(file_name, s); > + err = add_debug_file(file_name); > + if (err && err != -ENOMEM) > + kfree(file_name); > + if (!err && (nr_entries == 1) && !all) > + imv_set(dynamic_debug_on, 1); > + } else if (!strncmp("remove ", buffer, 7)) { > + s = strstrip(buffer+7);
spacing
> + err = remove_debug_file(s); > + if (!err && (nr_entries == 0) && !all) > + imv_set(dynamic_debug_on, 0); > + } > + if (!err) > + err = length; > +out_up: > + up(&debug_list_mutex); > +out: > + free_page((unsigned long)buffer); > + return err; > +} > + > +static void *pr_debug_seq_start(struct seq_file *f, loff_t *pos) > +{ > + return (*pos < FILE_TABLE_SIZE) ? pos : NULL; > +} > + > +static void *pr_debug_seq_next(struct seq_file *s, void *v, loff_t *pos) > +{ > + (*pos)++; > + if (*pos >= FILE_TABLE_SIZE) > + return NULL; > + return pos; > +} > + > +static void pr_debug_seq_stop(struct seq_file *s, void *v) > +{ > + /* Nothing to do */ > +} > + > +static int pr_debug_seq_show(struct seq_file *s, void *v) > +{ > + struct hlist_head *head; > + struct hlist_node *node; > + struct debug_name *element; > + unsigned int i = *(loff_t *) v; > + > + if (i == 0 && all) > + seq_printf(s, "all\n"); > + rcu_read_lock(); > + head = &file_table[i]; > + hlist_for_each_entry_rcu(element, node, head, hlist) > + seq_printf(s, "%s\n", element->name); > + rcu_read_unlock(); > + return 0; > +} > + > +static struct seq_operations pr_debug_seq_ops = { > + .start = pr_debug_seq_start, > + .next = pr_debug_seq_next, > + .stop = pr_debug_seq_stop, > + .show = pr_debug_seq_show > +}; > + > +static int pr_debug_open(struct inode *inode, struct file *filp) > +{ > + return seq_open(filp, &pr_debug_seq_ops); > +} > + > +static const struct file_operations pr_debug_operations = { > + .open = pr_debug_open, > + .read = seq_read, > + .write = pr_debug_write, > + .llseek = seq_lseek, > + .release = seq_release, > +}; > + > +int __init dynamic_printk_init(void) > +{ > + struct dentry *dir, *file; > + > + dir = debugfs_create_dir("dynamic_printk", NULL); > + if (!dir) > + return -ENOMEM; > + file = debugfs_create_file("files", 0644, dir, NULL, > + &pr_debug_operations); > + if (!file) { > + debugfs_remove(dir); > + return -ENOMEM; > + } > + return 0; > +} > +__initcall(dynamic_printk_init); > + > +static int __init dynamic_printk_setup(char *str) > +{ > + if (str) > + return -ENOENT; > + all = 1; > + imv_set(dynamic_debug_on, 1); > + return 0;
extra tab.
> +} > +early_param("dynamic_printk", dynamic_printk_setup);
--- ~Randy
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