This can protect an infinit recursion by unnecessary warning, too. -----8<----- >From 81f06a6f9c7f2e782267a2539c6c869d4214354c Mon Sep 17 00:00:00 2001 From: Byungchul Park <byungchul.p...@lge.com> Date: Fri, 18 Mar 2016 11:35:24 +0900 Subject: [PATCH] lib/spinlock_debug: Prevent a unnecessary recursive spin_dump()
Printing "lockup suspected" for the same lock more than once is meaningless. Furtheremore, it can cause an infinite recursion if it's on the way printing something by printk(). Signed-off-by: Byungchul Park <byungchul.p...@lge.com> --- kernel/locking/spinlock_debug.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/kernel/locking/spinlock_debug.c b/kernel/locking/spinlock_debug.c index fd24588..30559c6 100644 --- a/kernel/locking/spinlock_debug.c +++ b/kernel/locking/spinlock_debug.c @@ -138,14 +138,25 @@ static void __spin_lock_debug(raw_spinlock_t *lock) { u64 i; u64 loops = loops_per_jiffy * HZ; + static raw_spinlock_t *suspected_lock = NULL; for (i = 0; i < loops; i++) { if (arch_spin_trylock(&lock->raw_lock)) return; __delay(1); } - /* lockup suspected: */ - spin_dump(lock, "lockup suspected"); + + /* + * When we suspect a lockup, it's good enough to inform it once for + * the same lock. Otherwise it could cause an infinite recursion if + * it's within printk(). + */ + if (suspected_lock != lock) { + suspected_lock = lock; + /* lockup suspected: */ + spin_dump(lock, "lockup suspected"); + suspected_lock = NULL; + } #ifdef CONFIG_SMP trigger_all_cpu_backtrace(); #endif -- 1.9.1