linux-kernel - [tip:timers/core 5/5] kernel/time/timekeeping.c:220:7: warning: comparison of distinct pointer types ('unsigned long *' and 'typeof (tk->last_warning + (100 * 300)) *' (aka 'long *'))

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Message-ID: <202408241701.NSEI3MOV-lkp@intel.com>
Date: Sat, 24 Aug 2024 17:58:41 +0800
From: kernel test robot <lkp@...el.com>
To: Chen Yufan <chenyufan@...o.com>
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [tip:timers/core 5/5] kernel/time/timekeeping.c:220:7: warning:
 comparison of distinct pointer types ('unsigned long *' and 'typeof
 (tk->last_warning + (100 * 300)) *' (aka 'long *'))

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/core
head:   42db2c2cb5ac3572380a9489b8f8bbe0e534dfc7
commit: 42db2c2cb5ac3572380a9489b8f8bbe0e534dfc7 [5/5] timekeeping: Use time_after() in timekeeping_check_update()
config: i386-buildonly-randconfig-002-20240824 (https://download.01.org/0day-ci/archive/20240824/202408241701.NSEI3MOV-lkp@intel.com/config)
compiler: clang version 18.1.5 (https://github.com/llvm/llvm-project 617a15a9eac96088ae5e9134248d8236e34b91b1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240824/202408241701.NSEI3MOV-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202408241701.NSEI3MOV-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> kernel/time/timekeeping.c:220:7: warning: comparison of distinct pointer types ('unsigned long *' and 'typeof (tk->last_warning + (100 * 300)) *' (aka 'long *')) [-Wcompare-distinct-pointer-types]
     220 |                 if (time_after(jiffies, tk->last_warning + WARNING_FREQ)) {
         |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/jiffies.h:129:3: note: expanded from macro 'time_after'
     129 |          typecheck(unsigned long, b) && \
         |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/typecheck.h:12:18: note: expanded from macro 'typecheck'
      12 |         (void)(&__dummy == &__dummy2); \
         |                ~~~~~~~~ ^  ~~~~~~~~~
   kernel/time/timekeeping.c:230:7: warning: comparison of distinct pointer types ('unsigned long *' and 'typeof (tk->last_warning + (100 * 300)) *' (aka 'long *')) [-Wcompare-distinct-pointer-types]
     230 |                 if (time_after(jiffies, tk->last_warning + WARNING_FREQ)) {
         |                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/jiffies.h:129:3: note: expanded from macro 'time_after'
     129 |          typecheck(unsigned long, b) && \
         |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/typecheck.h:12:18: note: expanded from macro 'typecheck'
      12 |         (void)(&__dummy == &__dummy2); \
         |                ~~~~~~~~ ^  ~~~~~~~~~
   2 warnings generated.


vim +220 kernel/time/timekeeping.c

   203	
   204		u64 max_cycles = tk->tkr_mono.clock->max_cycles;
   205		const char *name = tk->tkr_mono.clock->name;
   206	
   207		if (offset > max_cycles) {
   208			printk_deferred("WARNING: timekeeping: Cycle offset (%lld) is larger than allowed by the '%s' clock's max_cycles value (%lld): time overflow danger\n",
   209					offset, name, max_cycles);
   210			printk_deferred("         timekeeping: Your kernel is sick, but tries to cope by capping time updates\n");
   211		} else {
   212			if (offset > (max_cycles >> 1)) {
   213				printk_deferred("INFO: timekeeping: Cycle offset (%lld) is larger than the '%s' clock's 50%% safety margin (%lld)\n",
   214						offset, name, max_cycles >> 1);
   215				printk_deferred("      timekeeping: Your kernel is still fine, but is feeling a bit nervous\n");
   216			}
   217		}
   218	
   219		if (tk->underflow_seen) {
 > 220			if (time_after(jiffies, tk->last_warning + WARNING_FREQ)) {
   221				printk_deferred("WARNING: Underflow in clocksource '%s' observed, time update ignored.\n", name);
   222				printk_deferred("         Please report this, consider using a different clocksource, if possible.\n");
   223				printk_deferred("         Your kernel is probably still fine.\n");
   224				tk->last_warning = jiffies;
   225			}
   226			tk->underflow_seen = 0;
   227		}
   228	
   229		if (tk->overflow_seen) {
   230			if (time_after(jiffies, tk->last_warning + WARNING_FREQ)) {
   231				printk_deferred("WARNING: Overflow in clocksource '%s' observed, time update capped.\n", name);
   232				printk_deferred("         Please report this, consider using a different clocksource, if possible.\n");
   233				printk_deferred("         Your kernel is probably still fine.\n");
   234				tk->last_warning = jiffies;
   235			}
   236			tk->overflow_seen = 0;
   237		}
   238	}
   239	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki