Re: [kbuild-all] Re: kernel/rcu/tree.c:2073:23: warning: stack frame size of 2704 bytes in function 'rcu_gp_kthread'
From: Nathan Chancellor
Date: Wed Jun 09 2021 - 00:14:38 EST
On 6/8/2021 8:58 PM, Paul E. McKenney wrote:
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@xxxxxxxxx>
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@xxxxxxxxxx>
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@xxxxxxxxx>
Tested-by: Rong Chen <rong.a.chen@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
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@xxxxxxxxxx>
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@xxxxxxxxx>
Tested-by: Rong Chen <rong.a.chen@xxxxxxxxx>
[ paulmck: noinline_for_stack per Nathan Chancellor. ]
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Reviewed-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Thanks!
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;