From mboxrd@z Thu Jan 1 00:00:00 1970 From: marc.zyngier@arm.com (Marc Zyngier) Date: Tue, 26 Aug 2014 19:07:03 +0100 Subject: [PATCH v2 01/26] genirq: add irq_domain-aware core IRQ handler In-Reply-To: <53FCC714.3090206@codeaurora.org> References: <1409047421-27649-1-git-send-email-marc.zyngier@arm.com> <1409047421-27649-2-git-send-email-marc.zyngier@arm.com> <53FCC714.3090206@codeaurora.org> Message-ID: <53FCCCC7.9070801@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 26/08/14 18:42, Stephen Boyd wrote: > On 08/26/14 03:03, Marc Zyngier wrote: >> Calling irq_find_mapping from outside a irq_{enter,exit} section is >> unsafe and produces ugly messages if CONFIG_PROVE_RCU is enabled: >> If coming from the idle state, the rcu_read_lock call in irq_find_mapping >> will generate an unpleasant warning: >> >> >> =============================== >> [ INFO: suspicious RCU usage. ] >> 3.16.0-rc1+ #135 Not tainted >> ------------------------------- >> include/linux/rcupdate.h:871 rcu_read_lock() used illegally while idle! >> >> other info that might help us debug this: >> >> RCU used illegally from idle CPU! >> rcu_scheduler_active = 1, debug_locks = 0 >> RCU used illegally from extended quiescent state! >> 1 lock held by swapper/0/0: >> #0: (rcu_read_lock){......}, at: [] >> irq_find_mapping+0x4c/0x198 > > Do you have the whole stacktrace? I don't see where this is called > outside of irq_enter() from within the idle loop, but maybe I missed > something. > Hi Stephen, Digging into my email, one of the traces looked like this: stack backtrace: CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.16.0-rc1+ #135 Call trace: [] dump_backtrace+0x0/0x12c [] show_stack+0x10/0x1c [] dump_stack+0x74/0xc4 [] lockdep_rcu_suspicious+0xe8/0x124 [] irq_find_mapping+0x16c/0x198 [] gic_handle_irq+0x38/0xcc Most drivers call irq_find_mapping outside of irq_enter()/irq_exit(), as this is in handle_IRQ(). Thanks, M. -- Jazz is not dead. It just smells funny...