rcu: Reduce stack usage in show_rcu_gp_kthreads()

When CONFIG_KASAN=y and CONFIG_KASAN_STACK=y builds, the
show_rcu_gp_kthreads() exceeds the 1024-byte frame-size limit:

make kernel/rcu/tree.o KCFLAGS="-fstack-usage"
  DESCEND objtool
  DESCEND bpf/resolve_btfids
  INSTALL libsubcmd_headers
  CC      kernel/rcu/tree.o
In file included from kernel/rcu/tree.c:4998:
kernel/rcu/tree_stall.h: In function 'show_rcu_gp_kthreads':
kernel/rcu/tree_stall.h:994:1: warning: the frame size of 1656 bytes is larger than 1024 bytes [-Wframe-larger-than=]

grep show_rcu kernel/rcu/tree.su
tree_nocb.h:1622:13:show_rcu_nocb_state 896     dynamic,bounded
tree_stall.h:933:6:show_rcu_gp_kthreads 1784    dynamic,bounded
tree_stall.h:1102:13:sysrq_show_rcu     16      static

Wrap the pr_info() into two noinline_for_stack helpers function:
show_rcu_state() print rcu_state status, and show_rcu_node()
print single rcu_node status.

After apply this change:

grep show_rcu kernel/rcu/tree.su
tree_stall.h:955:22:show_rcu_node	696	dynamic,bounded
tree_stall.h:930:22:show_rcu_state	872	dynamic,bounded
tree_nocb.h:1622:13:show_rcu_nocb_state	896	dynamic,bounded
tree_stall.h:972:6:show_rcu_gp_kthreads	544	static
tree_stall.h:1113:13:sysrq_show_rcu	16	static

Signed-off-by: Zqiang <qiang.zhang@linux.dev>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

0 files changed, 0 insertions, 0 deletions