Commit 55702ec9 authored by Stefan Wiehler's avatar Stefan Wiehler Committed by Thomas Bogendoerfer
Browse files

mips/smp: Call rcutree_report_cpu_starting() earlier 



rcutree_report_cpu_starting() must be called before
clockevents_register_device() to avoid the following lockdep splat triggered by
calling list_add() when CONFIG_PROVE_RCU_LIST=y:

  WARNING: suspicious RCU usage
  ...
  -----------------------------
  kernel/locking/lockdep.c:3680 RCU-list traversed in non-reader section!!

  other info that might help us debug this:

  RCU used illegally from offline CPU!
  rcu_scheduler_active = 1, debug_locks = 1
  no locks held by swapper/1/0.
  ...
  Call Trace:
  [<ffffffff8012a434>] show_stack+0x64/0x158
  [<ffffffff80a93d98>] dump_stack_lvl+0x90/0xc4
  [<ffffffff801c9e9c>] __lock_acquire+0x1404/0x2940
  [<ffffffff801cbf3c>] lock_acquire+0x14c/0x448
  [<ffffffff80aa4260>] _raw_spin_lock_irqsave+0x50/0x88
  [<ffffffff8021e0c8>] clockevents_register_device+0x60/0x1e8
  [<ffffffff80130ff0>] r4k_clockevent_init+0x220/0x3a0
  [<ffffffff801339d0>] start_secondary+0x50/0x3b8

raw_smp_processor_id() is required in order to avoid calling into lockdep
before RCU has declared the CPU to be watched for readers.

See also commit 29368e09 ("x86/smpboot:  Move rcu_cpu_starting() earlier"),
commit de5d9dae ("s390/smp: move rcu_cpu_starting() earlier") and commit
99f070b6 ("powerpc/smp: Call rcu_cpu_starting() earlier").

Signed-off-by: default avatarStefan Wiehler <stefan.wiehler@nokia.com>
Reviewed-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
Signed-off-by: default avatarThomas Bogendoerfer <tsbogend@alpha.franken.de>
parent 33cc938e

arch/mips/kernel/smp.c

+2 −2
Original line number Diff line number Diff line
@@ -351,10 +351,11 @@ early_initcall(mips_smp_ipi_init); 
 */

asmlinkage void start_secondary(void)

{

	unsigned int cpu;

	unsigned int cpu = raw_smp_processor_id();



	cpu_probe();

	per_cpu_trap_init(false);

	rcutree_report_cpu_starting(cpu);

	mips_clockevent_init();

	mp_ops->init_secondary();

	cpu_report();
@@ -366,7 +367,6 @@ asmlinkage void start_secondary(void) 
	 */



	calibrate_delay();

	cpu = smp_processor_id();

	cpu_data[cpu].udelay_val = loops_per_jiffy;



	set_cpu_sibling_map(cpu);