diff mbox series

[22/22] sched/idle: Mark arch_cpu_idle_dead() __noreturn

Message ID 2eeb4425572785d1f05d8761dba1cf88c2105304.1675461757.git.jpoimboe@kernel.org (mailing list archive)
State Handled Elsewhere
Headers show
Series cpu,sched: Mark arch_cpu_idle_dead() __noreturn | expand

Commit Message

Josh Poimboeuf Feb. 3, 2023, 10:05 p.m. UTC 
Before commit 076cbf5d2163 ("x86/xen: don't let xen_pv_play_dead()
return"), in Xen, when a previously offlined CPU was brought back
online, it unexpectedly resumed execution where it left off in the
middle of the idle loop.

There were some hacks to make that work, but the behavior was surprising
as do_idle() doesn't expect an offlined CPU to return from the dead (in
arch_cpu_idle_dead()).

Now that Xen has been fixed, and the arch-specific implementations of
arch_cpu_idle_dead() also don't return, give it a __noreturn attribute.

This will cause the compiler to complain if an arch-specific
implementation might return.  It also improves code generation for both
caller and callee.

Also fixes the following warning:

  vmlinux.o: warning: objtool: do_idle+0x25f: unreachable instruction

Reported-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 include/linux/cpu.h   | 2 +-
 tools/objtool/check.c | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index f83e4519c5f0..8582a7142623 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -182,7 +182,7 @@  void arch_cpu_idle(void);
 void arch_cpu_idle_prepare(void);
 void arch_cpu_idle_enter(void);
 void arch_cpu_idle_exit(void);
-void arch_cpu_idle_dead(void);
+void __noreturn arch_cpu_idle_dead(void);
 
 int cpu_report_state(int cpu);
 int cpu_check_up_prepare(int cpu);
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 0f67c6a8bc98..e3fa2279d612 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -167,6 +167,7 @@  static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 		"__reiserfs_panic",
 		"__stack_chk_fail",
 		"__ubsan_handle_builtin_unreachable",
+		"arch_cpu_idle_dead",
 		"cpu_bringup_and_idle",
 		"cpu_startup_entry",
 		"do_exit",