On Tue 2021-06-08 10:43:46, kernel test robot wrote: > Hi John, > > I love your patch! Perhaps something to improve: > > [auto build test WARNING on next-20210607] > > url: https://github.com/0day-ci/linux/commits/John-Ogness/introduce-printk-cpu-lock/20210608-040454 > base: 7f09e895a7f3e0af63bf9ec6c7c22893ec7e6c8e > config: mips-randconfig-r036-20210607 (attached as .config) > compiler: mips-linux-gcc (GCC) 9.3.0 > reproduce (this is a W=1 build): > wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross > chmod +x ~/bin/make.cross > # https://github.com/0day-ci/linux/commit/136bcc2980e636b2ae156ca63fbe95c713e44c1b > git remote add linux-review https://github.com/0day-ci/linux > git fetch --no-tags linux-review John-Ogness/introduce-printk-cpu-lock/20210608-040454 > git checkout 136bcc2980e636b2ae156ca63fbe95c713e44c1b > # save the attached .config to linux build tree > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=mips > > If you fix the issue, kindly add following tag as appropriate > Reported-by: kernel test robot <lkp@xxxxxxxxx> > > All warnings (new ones prefixed by >>): > > lib/dump_stack.c: In function 'dump_stack_lvl': > >> lib/dump_stack.c:107:2: warning: 'lock_flag' is used uninitialized in this function [-Wuninitialized] > 107 | printk_cpu_unlock_irqrestore(lock_flag, irq_flags); > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Interesting. I am curious that it does not complain also about irq_flags. But it is possible the it reports only the first problem. Anyway, we will likely need to do some trickery via #define to tell the compiler that the value is set. I mean to do similar thing as: #define raw_local_irq_save(flags) \ do { \ typecheck(unsigned long, flags); \ flags = arch_local_irq_save(); \ } while (0) In our case, it might look like: #define printk_cpu_lock_irqsave(lock_nested, irq_flags) \ do { \ local_irq_save(irq_flags); \ typecheck(bool, lock_nested); \ lock_nested = __printk_cpu_lock(irq_flags); \ } while (0) then we would need to do in __prink_cpu_lock(unsigned long irq_flags) } else { local_irq_restore(irq_flags); /* * Wait for the lock to release before jumping to cmpxchg() * in order to mitigate the thundering herd problem. */ do { cpu_relax(); } while (atomic_read(&printk_cpulock_owner) != -1); local_irq_save(irq_flags) goto retry; } Best Regards, Petr
