3.18.27-rt27-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Yang Shi BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:917 in_atomic(): 1, irqs_disabled(): 128, pid: 383, name: sh Preemption disabled at:[] kgdb_cpu_enter+0x158/0x6b8 CPU: 3 PID: 383 Comm: sh Tainted: G W 4.1.13-rt13 #2 Hardware name: Freescale Layerscape 2085a RDB Board (DT) Call trace: [] dump_backtrace+0x0/0x128 [] show_stack+0x24/0x30 [] dump_stack+0x80/0xa0 [] ___might_sleep+0x18c/0x1a0 [] __rt_spin_lock+0x2c/0x40 [] rt_read_lock+0x40/0x58 [] single_step_handler+0x38/0xd8 [] do_debug_exception+0x58/0xb8 Exception stack(0xffff80834a1e7c80 to 0xffff80834a1e7da0) 7c80: ffffff9c ffffffff 92c23ba0 0000ffff 4a1e7e40 ffff8083 001bfcc4 ffff8000 7ca0: f2000400 00000000 00000000 00000000 4a1e7d80 ffff8083 0049501c ffff8000 7cc0: 00005402 00000000 00aaa210 ffff8000 4a1e7ea0 ffff8083 000833f4 ffff8000 7ce0: ffffff9c ffffffff 92c23ba0 0000ffff 4a1e7ea0 ffff8083 001bfcc0 ffff8000 7d00: 4a0fc400 ffff8083 00005402 00000000 4a1e7d40 ffff8083 00490324 ffff8000 7d20: ffffff9c 00000000 92c23ba0 0000ffff 000a0000 00000000 00000000 00000000 7d40: 00000008 00000000 00080000 00000000 92c23b8b 0000ffff 92c23b8e 0000ffff 7d60: 00000038 00000000 00001cb2 00000000 00000005 00000000 92d7b498 0000ffff 7d80: 01010101 01010101 92be9000 0000ffff 00000000 00000000 00000030 00000000 [] el1_dbg+0x18/0x6c This issue is similar with 62c6c61("arm64: replace read_lock to rcu lock in call_break_hook"), but comes to single_step_handler. This also solves kgdbts boot test silent hang issue on 4.4 -rt kernel. Cc: stable-rt@vger.kernel.org Signed-off-by: Yang Shi Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt --- arch/arm64/kernel/debug-monitors.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c index b056369fd47d..4c6f340c90fa 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -184,20 +184,21 @@ static void clear_regs_spsr_ss(struct pt_regs *regs) /* EL1 Single Step Handler hooks */ static LIST_HEAD(step_hook); -static DEFINE_RWLOCK(step_hook_lock); +static DEFINE_SPINLOCK(step_hook_lock); void register_step_hook(struct step_hook *hook) { - write_lock(&step_hook_lock); - list_add(&hook->node, &step_hook); - write_unlock(&step_hook_lock); + spin_lock(&step_hook_lock); + list_add_rcu(&hook->node, &step_hook); + spin_unlock(&step_hook_lock); } void unregister_step_hook(struct step_hook *hook) { - write_lock(&step_hook_lock); - list_del(&hook->node); - write_unlock(&step_hook_lock); + spin_lock(&step_hook_lock); + list_del_rcu(&hook->node); + spin_unlock(&step_hook_lock); + synchronize_rcu(); } /* @@ -211,15 +212,15 @@ static int call_step_hook(struct pt_regs *regs, unsigned int esr) struct step_hook *hook; int retval = DBG_HOOK_ERROR; - read_lock(&step_hook_lock); + rcu_read_lock(); - list_for_each_entry(hook, &step_hook, node) { + list_for_each_entry_rcu(hook, &step_hook, node) { retval = hook->fn(regs, esr); if (retval == DBG_HOOK_HANDLED) break; } - read_unlock(&step_hook_lock); + rcu_read_unlock(); return retval; } -- 2.7.0