Messages in this thread Patch in this message | | | Date | Tue, 8 Jun 2021 20:58:05 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [kbuild-all] Re: kernel/rcu/tree.c:2073:23: warning: stack frame size of 2704 bytes in function 'rcu_gp_kthread' |
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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/?id=7dffe01765d9309b8bd5505503933ec0ec53d192 > > > > > > > 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@intel.com> > > > > > > > > > > > > > > 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@kernel.org> > > 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@intel.com> > > Tested-by: Rong Chen <rong.a.chen@intel.com> > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > > > > 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
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commit 8aa0ceef4264012abd7b98d29f0a968f0f0046cb Author: Paul E. McKenney <paulmck@kernel.org> 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@intel.com> Tested-by: Rong Chen <rong.a.chen@intel.com> [ paulmck: noinline_for_stack per Nathan Chancellor. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 13bd8eee62bf..d8052adcdcb1 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_for_stack bool rcu_gp_init(void) { unsigned long firstseq; unsigned long flags; @@ -1931,7 +1931,7 @@ static void rcu_gp_fqs(bool first_time) /* * Loop doing repeated quiescent-state forcing until the grace period ends. */ -static void rcu_gp_fqs_loop(void) +static noinline_for_stack void rcu_gp_fqs_loop(void) { bool first_gp_fqs; int gf = 0;
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