From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Andrzej Siewior Subject: [PATCH RT] arm/unwind: fail on unwind in irq disabled regions Date: Fri, 24 Jan 2014 17:24:23 +0100 Message-ID: <1390580663-28869-1-git-send-email-bigeasy@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: linux-rt-users@vger.kernel.org, Sebastian Andrzej Siewior To: linux-kernel@vger.kernel.org Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org Mostly unwind is done with irqs enabled however SLUB may call it with irqs disabled while creating a new SLUB cache. I had system freeze while loading a module which called kmem_cache_create() on init. That means SLUB's __slab_alloc() disabled interrupts and then ->new_slab_objects() ->new_slab() ->setup_object() ->setup_object_debug() ->init_tracking() ->set_track() ->save_stack_trace() ->save_stack_trace_tsk() ->walk_stackframe() ->unwind_frame() ->unwind_find_idx() =3D>spin_lock_irqsave(&unwind_lock); I would prefer not to turn this into a raw lock so for now it will just fail if it is called with irqs disabled which might return a few "empty= " traces=E2=80=A6 Signed-off-by: Sebastian Andrzej Siewior --- arch/arm/kernel/unwind.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c index 00df012..2af232d 100644 --- a/arch/arm/kernel/unwind.c +++ b/arch/arm/kernel/unwind.c @@ -195,6 +195,11 @@ static const struct unwind_idx *unwind_find_idx(un= signed long addr) /* module unwind tables */ struct unwind_table *table; =20 +#ifdef CONFIG_PREEMPT_RT_FULL + if (irqs_disabled()) + goto out; +#endif + spin_lock_irqsave(&unwind_lock, flags); list_for_each_entry(table, &unwind_tables, list) { if (addr >=3D table->begin_addr && @@ -211,6 +216,7 @@ static const struct unwind_idx *unwind_find_idx(uns= igned long addr) } =20 pr_debug("%s: idx =3D %p\n", __func__, idx); +out: return idx; } =20 @@ -345,7 +351,9 @@ int unwind_frame(struct stackframe *frame) =20 idx =3D unwind_find_idx(frame->pc); if (!idx) { +#ifndef CONFIG_PREEMPT_RT_FULL pr_warning("unwind: Index not found %08lx\n", frame->pc); +#endif return -URC_FAILURE; } =20 --=20 1.8.5.3