[kbuild-all] Re: kernel/rcu/tree.c:2073:23: warning: stack frame size of 2704 bytes in function 'rcu_gp_kthread'

On Tue, Jun 08, 2021 at 08:53:17AM -0700, Nathan Chancellor wrote: > On 6/7/2021 10:01 PM, Paul E. McKenney wrote: >> On Tue, Jun 08, 2021 at 11:14:40AM +0800, Rong Chen wrote: >>> >>> >>> On 6/7/21 11:19 PM, Paul E. McKenney wrote: >>>> On Mon, Jun 07, 2021 at 05:18:21PM +0800, Rong Chen wrote: >>>>> >>>>> On 6/6/21 12:49 PM, Paul E. McKenney wrote: >>>>>> On Sun, Jun 06, 2021 at 12:19:57PM +0800, kernel test robot wrote: >>>>>>> Hi Paul, >>>>>>> >>>>>>> FYI, the error/warning still remains. >>>>>>> >>>>>>> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master >>>>>>> head: f5b6eb1e018203913dfefcf6fa988649ad11ad6e >>>>>>> commit: 7dffe01765d9309b8bd5505503933ec0ec53d192 rcu: Add lockdep_assert_irqs_disabled() to raw_spin_unlock_rcu_node() macros >>>>>>> date: 5 months ago >>>>>>> config: powerpc-randconfig-r023-20210606 (attached as .config) >>>>>>> compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project 551a697c5cf33275b66add4fc467fcf59084cffb) >>>>>>> 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 >>>>>>> # install powerpc cross compiling tool for clang build >>>>>>> # apt-get install binutils-powerpc-linux-gnu >>>>>>> # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit... >>>>>>> git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git >>>>>>> git fetch --no-tags linus master >>>>>>> git checkout 7dffe01765d9309b8bd5505503933ec0ec53d192 >>>>>>> # save the attached .config to linux build tree >>>>>>> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=powerpc >>>>>>> >>>>>>> If you fix the issue, kindly add following tag as appropriate >>>>>>> Reported-by: kernel test robot <lkp(a)intel.com&gt; >>>>>>> >>>>>>> All warnings (new ones prefixed by >>): >>>>>>> >>>>>>> In file included from kernel/rcu/tree.c:21: >>>>>>> In file included from include/linux/kernel.h:12: >>>>>>> In file included from include/linux/bitops.h:29: >>>>>>> In file included from arch/powerpc/include/asm/bitops.h:62: >>>>>>> arch/powerpc/include/asm/barrier.h:49:9: warning: '__lwsync' macro redefined [-Wmacro-redefined] >>>>>>> #define __lwsync() __asm__ __volatile__ (stringify_in_c(LWSYNC) : : :"memory") >>>>>>> ^ >>>>>>> <built-in>:310:9: note: previous definition is here >>>>>>> #define __lwsync __builtin_ppc_lwsync >>>>>>> ^ >>>>>>>>> kernel/rcu/tree.c:2073:23: warning: stack frame size of 2704 bytes in function 'rcu_gp_kthread' [-Wframe-larger-than=] >>>>>>> static int __noreturn rcu_gp_kthread(void *unused) >>>>>> Does -rcu commit 2f20de99a63b ("rcu: Make rcu_gp_cleanup() be noinline >>>>>> for tracing") help? >>>>> Hi Paul, >>>>> >>>>> The stack frame size decreased to 2256 bytes: >>>>> >>>>>   kernel/rcu/tree.c:2129:23: warning: stack frame size of 2256 bytes in >>>>> function 'rcu_gp_kthread' [-Wframe-larger-than=] >>>> Very good, thank you! Does the following patch (in addition to that >>>> commit) also help? >>> >>> Hi Paul, >>> >>> I applied the below patch on commit 2f20de99a63b and the warning is gone. >> >> Very good, and thank you for your testing. I have applied the requested >> Reported-by and your Tested-by on the commit shown below. Please let >> me know if you would prefer some other Reported/Tested setup. >> >> Thanx, Paul >> >> ------------------------------------------------------------------------ >> >> commit 336e92638287615d47c07af4ff6feb397cfe2084 >> Author: Paul E. McKenney <paulmck(a)kernel.org&gt; >> Date: Mon Jun 7 21:57:02 2021 -0700 >> >> rcu: Make rcu_gp_init() and rcu_gp_fqs_loop noinline to conserve stack >> The kbuild test project found an oversized stack frame in rcu_gp_kthread() >> for some kernel configurations. This oversizing was due to a very large >> amount of inlining, which is unnecessary due to the fact that this code >> executes infrequently. This commit therefore marks rcu_gp_init() and >> rcu_gp_fqs_loop noinline to conserve stack space. >> Reported-by: kernel test robot <lkp(a)intel.com&gt; >> Tested-by: Rong Chen <rong.a.chen(a)intel.com&gt; >> Signed-off-by: Paul E. McKenney <paulmck(a)kernel.org&gt; >> >> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c >> index 13bd8eee62bf..ef435aeac993 100644 >> --- a/kernel/rcu/tree.c >> +++ b/kernel/rcu/tree.c >> @@ -1737,7 +1737,7 @@ static void rcu_strict_gp_boundary(void *unused) >> /* >> * Initialize a new grace period. Return false if no grace period required. >> */ >> -static bool rcu_gp_init(void) >> +static noinline bool rcu_gp_init(void) > > Small comment if it is not too late. noinline_for_stack expands to the same > thing but is self documenting :) that way people do not have to git blame to > see why these are marked as noinline (not that too many people are probably > touching this but still). How about like the following? Thanx, Paul ------------------------------------------------------------------------ commit 8aa0ceef4264012abd7b98d29f0a968f0f0046cb Author: Paul E. McKenney <paulmck(a)kernel.org&gt; Date: Mon Jun 7 21:57:02 2021 -0700 rcu: Make rcu_gp_init() and rcu_gp_fqs_loop noinline to conserve stack The kbuild test project found an oversized stack frame in rcu_gp_kthread() for some kernel configurations. This oversizing was due to a very large amount of inlining, which is unnecessary due to the fact that this code executes infrequently. This commit therefore marks rcu_gp_init() and rcu_gp_fqs_loop noinline_for_stack to conserve stack space. Reported-by: kernel test robot <lkp(a)intel.com&gt; Tested-by: Rong Chen <rong.a.chen(a)intel.com&gt; [ paulmck: noinline_for_stack per Nathan Chancellor. ] Signed-off-by: Paul E. McKenney <paulmck(a)kernel.org&gt;