[4/4] printk: miscellaneous cleanups

Message ID 1404911056-29064-5-git-send-email-elder@linaro.org
State New
Headers show

Commit Message

Alex Elder July 9, 2014, 1:04 p.m.
This patch contains some small cleanups to kernel/printk/printk.c.
None of them should cause any change in behavior.
  - When CONFIG_PRINTK is defined, parenthesize the value of LOG_LINE_MAX.
  - When CONFIG_PRINTK is *not* defined, there is an extra LOG_LINE_MAX
    definition; delete it.
  - Pull an assignment out of a conditional expression in console_setup().
  - Use isdigit() in console_setup() rather than open coding it.
  - In update_console_cmdline(), drop a NUL-termination assignment;
    the strlcpy() call that precedes it guarantees it's not needed.
  - Simplify some logic in printk_timed_ratelimit().

Signed-off-by: Alex Elder <elder@linaro.org>
---
 kernel/printk/printk.c | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

Comments

Petr Mladek July 9, 2014, 4:29 p.m. | #1
Sending once again as a correct reply. I am sorry for the
confusion. I think that it is high time for me to go home and sleep :-)

On Wed 2014-07-09 08:04:16, Alex Elder wrote:
> This patch contains some small cleanups to kernel/printk/printk.c.
> None of them should cause any change in behavior.
>   - When CONFIG_PRINTK is defined, parenthesize the value of LOG_LINE_MAX.
>   - When CONFIG_PRINTK is *not* defined, there is an extra LOG_LINE_MAX
>     definition; delete it.
>   - Pull an assignment out of a conditional expression in console_setup().
>   - Use isdigit() in console_setup() rather than open coding it.
>   - In update_console_cmdline(), drop a NUL-termination assignment;
>     the strlcpy() call that precedes it guarantees it's not needed.
>   - Simplify some logic in printk_timed_ratelimit().
> 
> Signed-off-by: Alex Elder <elder@linaro.org>
> ---
>  kernel/printk/printk.c | 26 +++++++++++++-------------
>  1 file changed, 13 insertions(+), 13 deletions(-)
> 
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 6f75e8a..909029e 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -45,6 +45,7 @@
>  #include <linux/poll.h>
>  #include <linux/irq_work.h>
>  #include <linux/utsname.h>
> +#include <linux/ctype.h>
>  
>  #include <asm/uaccess.h>
>  
> @@ -257,7 +258,7 @@ static u64 clear_seq;
>  static u32 clear_idx;
>  
>  #define PREFIX_MAX		32
> -#define LOG_LINE_MAX		1024 - PREFIX_MAX
> +#define LOG_LINE_MAX		(1024 - PREFIX_MAX)
>  
>  /* record buffer */
>  #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
> @@ -1794,7 +1795,7 @@ EXPORT_SYMBOL(printk);
>  
>  #define LOG_LINE_MAX		0
>  #define PREFIX_MAX		0
> -#define LOG_LINE_MAX 0
> +
>  static u64 syslog_seq;
>  static u32 syslog_idx;
>  static u64 console_seq;
> @@ -1895,7 +1896,8 @@ static int __init console_setup(char *str)
>  		strncpy(buf, str, sizeof(buf) - 1);
>  	}
>  	buf[sizeof(buf) - 1] = 0;
> -	if ((options = strchr(str, ',')) != NULL)
> +	options = strchr(str, ',');
> +	if (options)
>  		*(options++) = 0;
>  #ifdef __sparc__
>  	if (!strcmp(str, "ttya"))
> @@ -1904,7 +1906,7 @@ static int __init console_setup(char *str)
>  		strcpy(buf, "ttyS1");
>  #endif
>  	for (s = buf; *s; s++)
> -		if ((*s >= '0' && *s <= '9') || *s == ',')
> +		if (isdigit(*s) || *s == ',')
>  			break;
>  	idx = simple_strtoul(s, NULL, 10);
>  	*s = 0;
> @@ -1943,7 +1945,6 @@ int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, cha
>  	     i++, c++)
>  		if (strcmp(c->name, name) == 0 && c->index == idx) {
>  			strlcpy(c->name, name_new, sizeof(c->name));
> -			c->name[sizeof(c->name) - 1] = 0;
>  			c->options = options;
>  			c->index = idx_new;
>  			return i;
> @@ -2611,14 +2612,13 @@ EXPORT_SYMBOL(__printk_ratelimit);
>  bool printk_timed_ratelimit(unsigned long *caller_jiffies,
>  			unsigned int interval_msecs)
>  {
> -	if (*caller_jiffies == 0
> -			|| !time_in_range(jiffies, *caller_jiffies,
> -					*caller_jiffies
> -					+ msecs_to_jiffies(interval_msecs))) {
> -		*caller_jiffies = jiffies;
> -		return true;
> -	}
> -	return false;
> +	unsigned long elapsed = jiffies - *caller_jiffies;

I wondered if the deduction might be negative. Well, it should not be
if none manipulates *caller_jiffies in a strange way. If it happens,
the following condition will most likely fail and *caller_jiffies will
get reset to jiffies. It looks reasonable to me.

Reviewed-by: Petr Mladek <pmladek@suse.cz>

> +	if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
> +		return false;
> +
> +	*caller_jiffies = jiffies;
> +	return true;
>  }
>  EXPORT_SYMBOL(printk_timed_ratelimit);

Best Regards,
Petr
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Alex Elder July 9, 2014, 4:45 p.m. | #2
On 07/09/2014 11:29 AM, Petr Mládek wrote:
> Sending once again as a correct reply. I am sorry for the
> confusion. I think that it is high time for me to go home and sleep :-)
>
> On Wed 2014-07-09 08:04:16, Alex Elder wrote:
>> This patch contains some small cleanups to kernel/printk/printk.c.
>> None of them should cause any change in behavior.
>>    - When CONFIG_PRINTK is defined, parenthesize the value of LOG_LINE_MAX.
>>    - When CONFIG_PRINTK is *not* defined, there is an extra LOG_LINE_MAX
>>      definition; delete it.
>>    - Pull an assignment out of a conditional expression in console_setup().
>>    - Use isdigit() in console_setup() rather than open coding it.
>>    - In update_console_cmdline(), drop a NUL-termination assignment;
>>      the strlcpy() call that precedes it guarantees it's not needed.
>>    - Simplify some logic in printk_timed_ratelimit().
>>
>> Signed-off-by: Alex Elder <elder@linaro.org>
>> ---
>>   kernel/printk/printk.c | 26 +++++++++++++-------------
>>   1 file changed, 13 insertions(+), 13 deletions(-)
>>
>> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
>> index 6f75e8a..909029e 100644
>> --- a/kernel/printk/printk.c
>> +++ b/kernel/printk/printk.c

. . .

>> @@ -2611,14 +2612,13 @@ EXPORT_SYMBOL(__printk_ratelimit);
>>   bool printk_timed_ratelimit(unsigned long *caller_jiffies,
>>   			unsigned int interval_msecs)
>>   {
>> -	if (*caller_jiffies == 0
>> -			|| !time_in_range(jiffies, *caller_jiffies,
>> -					*caller_jiffies
>> -					+ msecs_to_jiffies(interval_msecs))) {
>> -		*caller_jiffies = jiffies;
>> -		return true;
>> -	}
>> -	return false;
>> +	unsigned long elapsed = jiffies - *caller_jiffies;
>

Currently, all callers pass a 0 value in *caller_jiffies
initially (using a static/BSS variable), and a value updated
by a previous call to __printk_ratelimit() thereafter.

If a caller passed something different, yes, it's possible the
result would wrap to a high unsigned value (i.e., go negative).
However the logic used here involves the same subtraction
operation as was used before--though previously that was
buried inside the time_after() macro called by time_in_range().

					-Alex

> I wondered if the deduction might be negative. Well, it should not be
> if none manipulates *caller_jiffies in a strange way. If it happens,
> the following condition will most likely fail and *caller_jiffies will
> get reset to jiffies. It looks reasonable to me.
>
> Reviewed-by: Petr Mladek <pmladek@suse.cz>
>
>> +	if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
>> +		return false;
>> +
>> +	*caller_jiffies = jiffies;
>> +	return true;
>>   }
>>   EXPORT_SYMBOL(printk_timed_ratelimit);
>
> Best Regards,
> Petr
>

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diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 6f75e8a..909029e 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -45,6 +45,7 @@ 
 #include <linux/poll.h>
 #include <linux/irq_work.h>
 #include <linux/utsname.h>
+#include <linux/ctype.h>
 
 #include <asm/uaccess.h>
 
@@ -257,7 +258,7 @@  static u64 clear_seq;
 static u32 clear_idx;
 
 #define PREFIX_MAX		32
-#define LOG_LINE_MAX		1024 - PREFIX_MAX
+#define LOG_LINE_MAX		(1024 - PREFIX_MAX)
 
 /* record buffer */
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
@@ -1794,7 +1795,7 @@  EXPORT_SYMBOL(printk);
 
 #define LOG_LINE_MAX		0
 #define PREFIX_MAX		0
-#define LOG_LINE_MAX 0
+
 static u64 syslog_seq;
 static u32 syslog_idx;
 static u64 console_seq;
@@ -1895,7 +1896,8 @@  static int __init console_setup(char *str)
 		strncpy(buf, str, sizeof(buf) - 1);
 	}
 	buf[sizeof(buf) - 1] = 0;
-	if ((options = strchr(str, ',')) != NULL)
+	options = strchr(str, ',');
+	if (options)
 		*(options++) = 0;
 #ifdef __sparc__
 	if (!strcmp(str, "ttya"))
@@ -1904,7 +1906,7 @@  static int __init console_setup(char *str)
 		strcpy(buf, "ttyS1");
 #endif
 	for (s = buf; *s; s++)
-		if ((*s >= '0' && *s <= '9') || *s == ',')
+		if (isdigit(*s) || *s == ',')
 			break;
 	idx = simple_strtoul(s, NULL, 10);
 	*s = 0;
@@ -1943,7 +1945,6 @@  int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, cha
 	     i++, c++)
 		if (strcmp(c->name, name) == 0 && c->index == idx) {
 			strlcpy(c->name, name_new, sizeof(c->name));
-			c->name[sizeof(c->name) - 1] = 0;
 			c->options = options;
 			c->index = idx_new;
 			return i;
@@ -2611,14 +2612,13 @@  EXPORT_SYMBOL(__printk_ratelimit);
 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
 			unsigned int interval_msecs)
 {
-	if (*caller_jiffies == 0
-			|| !time_in_range(jiffies, *caller_jiffies,
-					*caller_jiffies
-					+ msecs_to_jiffies(interval_msecs))) {
-		*caller_jiffies = jiffies;
-		return true;
-	}
-	return false;
+	unsigned long elapsed = jiffies - *caller_jiffies;
+
+	if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
+		return false;
+
+	*caller_jiffies = jiffies;
+	return true;
 }
 EXPORT_SYMBOL(printk_timed_ratelimit);