kernel/power/hibernate.c: use 'u64' instead of 's64' to avoid warning

For do_div(), it need 'u64' type, which means the outside must be sure of 'start' is not bigger than 'stop', or it will report warning.

Even if 'start' was really bigger than 'stop', it would print incorrect information, but for kernel, it still can continue, so use WARN_ON() is enough.

The related warning (with allmodconfig for unicore32):

CC kernel/power/hibernate.o
kernel/power/hibernate.c: In function ‘swsusp_show_speed’:
kernel/power/hibernate.c:237: warning: comparison of distinct pointer types lacks a cast

Quoted 7 lines · Chen Gang

For do_div(), it need 'u64' type, which means the outside must be sure of 'start' is not bigger than 'stop', or it will report warning.

Even if 'start' was really bigger than 'stop', it would print incorrect information, but for kernel, it still can continue, so use WARN_ON() is enough.

Quoted 7 lines

The related warning (with allmodconfig for unicore32):

CC kernel/power/hibernate.o
kernel/power/hibernate.c: In function ‘swsusp_show_speed’:
kernel/power/hibernate.c:237: warning: comparison of distinct pointer types lacks a cast

Certainly better, but

Quoted 6 lines

kernel/power/hibernate.c +1 -1

-	s64 elapsed_centisecs64;
+	u64 elapsed_centisecs64;
 	int centisecs;
 	int k;
 	int kps;

kernel/power/hibernate.c static void platform_recover(int platform_mode) · line 239

Quoted 4 lines

kernel/power/hibernate.c +1 -0

 	elapsed_centisecs64 = timeval_to_ns(stop) - timeval_to_ns(start);
+	WARN_ON((s64)elapsed_centisecs64 < 0);
 	do_div(elapsed_centisecs64, NSEC_PER_SEC / 100);
 	centisecs = elapsed_centisecs64;

...do we need to do the WARN_ON()? Only result of underflow will be very long elapsed time reported... that does not sound too
bad. ... and it will be quite obvious what went wrong.
Pavel

Quoted 18 lines · Pavel Machek

Quoted 7 lines · Chen Gang

For do_div(), it need 'u64' type, which means the outside must be sure of 'start' is not bigger than 'stop', or it will report warning.

Even if 'start' was really bigger than 'stop', it would print incorrect information, but for kernel, it still can continue, so use WARN_ON() is enough.

Quoted 7 lines

The related warning (with allmodconfig for unicore32):

CC kernel/power/hibernate.o
kernel/power/hibernate.c: In function ‘swsusp_show_speed’:
kernel/power/hibernate.c:237: warning: comparison of distinct pointer types lacks a cast

Certainly better, but

Quoted 8 lines

kernel/power/hibernate.c static void platform_recover(int platform_mode) · line 237

Quoted 8 lines

kernel/power/hibernate.c +2 -1

-	s64 elapsed_centisecs64;
+	u64 elapsed_centisecs64;
 	int centisecs;
 	int k;
 	int kps;
 
 	elapsed_centisecs64 = timeval_to_ns(stop) - timeval_to_ns(start);
+	WARN_ON((s64)elapsed_centisecs64 < 0);

Quoted 8 lines

kernel/power/hibernate.c static void platform_recover(int platform_mode) · line 239

Quoted 2 lines

kernel/power/hibernate.c +0 -0

 	do_div(elapsed_centisecs64, NSEC_PER_SEC / 100);
 	centisecs = elapsed_centisecs64;

...do we need to do the WARN_ON()? Only result of underflow will be very long elapsed time reported... that does not sound too
bad. ... and it will be quite obvious what went wrong.
Pavel

Hmm... that sounds reasonable to me. If no any other reply within 2 days, I shall send patch v3 for it.

BTW: sorry, I guess I can not finish allmodconfig for unicore32 within this month (2014-04-30) -- at present I only finish 40-50%, I will/should try to finish it within next month.

Thanks.

Quoted 19 lines · Chen Gang

Quoted 18 lines · Pavel Machek

Quoted 7 lines · Chen Gang

For do_div(), it need 'u64' type, which means the outside must be sure of 'start' is not bigger than 'stop', or it will report warning.

Even if 'start' was really bigger than 'stop', it would print incorrect information, but for kernel, it still can continue, so use WARN_ON() is enough.

Quoted 7 lines

The related warning (with allmodconfig for unicore32):

CC kernel/power/hibernate.o
kernel/power/hibernate.c: In function ‘swsusp_show_speed’:
kernel/power/hibernate.c:237: warning: comparison of distinct pointer types lacks a cast

Certainly better, but

Quoted 8 lines

Quoted 8 lines

kernel/power/hibernate.c static void platform_recover(int platform_mode) · line 237

Quoted 8 lines

kernel/power/hibernate.c +2 -1

-	s64 elapsed_centisecs64;
+	u64 elapsed_centisecs64;
 	int centisecs;
 	int k;
 	int kps;
 
 	elapsed_centisecs64 = timeval_to_ns(stop) - timeval_to_ns(start);
+	WARN_ON((s64)elapsed_centisecs64 < 0);

How about to use one line comments instead of WARN_ON()?

	/*
	 * If "(s64)elapsed_centisecs64 < 0", it will print long elapsed
	 * time, it is obvious enough to user for what went wrong.
	 */

Quoted 31 lines · Chen Gang

Quoted 19 lines · Chen Gang

Quoted 18 lines · Pavel Machek

Quoted 7 lines · Chen Gang

For do_div(), it need 'u64' type, which means the outside must be sure of 'start' is not bigger than 'stop', or it will report warning.

Even if 'start' was really bigger than 'stop', it would print incorrect information, but for kernel, it still can continue, so use WARN_ON() is enough.

Quoted 7 lines

The related warning (with allmodconfig for unicore32):

CC kernel/power/hibernate.o
kernel/power/hibernate.c: In function ‘swsusp_show_speed’:
kernel/power/hibernate.c:237: warning: comparison of distinct pointer types lacks a cast

Certainly better, but

Quoted 8 lines

Quoted 8 lines

kernel/power/hibernate.c static void platform_recover(int platform_mode) · line 237

Quoted 8 lines

kernel/power/hibernate.c +2 -1

-	s64 elapsed_centisecs64;
+	u64 elapsed_centisecs64;
 	int centisecs;
 	int k;
 	int kps;
 
 	elapsed_centisecs64 = timeval_to_ns(stop) - timeval_to_ns(start);
+	WARN_ON((s64)elapsed_centisecs64 < 0);

How about to use one line comments instead of WARN_ON()?

Quoted 4 lines

	/*
	 * If "(s64)elapsed_centisecs64 < 0", it will print long elapsed
	 * time, it is obvious enough to user for what went wrong.
	 */

And will the users actually read this comment?

Please just change the type to silence the warning. And you can change all of the other local variables in that function to unsigned int when you're at it.