| Message ID | 1409047421-27649-2-git-send-email-marc.zyngier@arm.com |
|---|---|
| State | New |
| Headers | show |
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: > > <quote> > =============================== > [ 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: [<ffffffc00010206c>] > 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.
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: >> >> <quote> >> =============================== >> [ 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: [<ffffffc00010206c>] >> 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: [<ffffffc0000882cc>] dump_backtrace+0x0/0x12c [<ffffffc000088408>] show_stack+0x10/0x1c [<ffffffc0004ee5f0>] dump_stack+0x74/0xc4 [<ffffffc0000edfbc>] lockdep_rcu_suspicious+0xe8/0x124 [<ffffffc00010218c>] irq_find_mapping+0x16c/0x198 [<ffffffc00008130c>] 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.
On 08/26/14 11:07, Marc Zyngier wrote: > 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: > [<ffffffc0000882cc>] dump_backtrace+0x0/0x12c > [<ffffffc000088408>] show_stack+0x10/0x1c > [<ffffffc0004ee5f0>] dump_stack+0x74/0xc4 > [<ffffffc0000edfbc>] lockdep_rcu_suspicious+0xe8/0x124 > [<ffffffc00010218c>] irq_find_mapping+0x16c/0x198 > [<ffffffc00008130c>] gic_handle_irq+0x38/0xcc > > Most drivers call irq_find_mapping outside of irq_enter()/irq_exit(), as > this is in handle_IRQ(). > Ah ok. This is the multi-irq handler case? Has this been broken since v3.2 at least for the gic users? Now that we call irq_enter()/irq_exit() a lot more code runs, including things like updating jiffies when interrupts arrive and invoking softirq? Do we only call irq_exit() on the IPI path otherwise? Are there any plans to send this back to stable trees? Not calling irq_enter()/irq_exit() when we get an interrupt seems like a big problem.
On Tue, Aug 26, 2014 at 11:46:38AM -0700, Stephen Boyd wrote: > Ah ok. This is the multi-irq handler case? Has this been broken since > v3.2 at least for the gic users? Now that we call irq_enter()/irq_exit() > a lot more code runs, including things like updating jiffies when > interrupts arrive and invoking softirq? Do we only call irq_exit() on > the IPI path otherwise? > > Are there any plans to send this back to stable trees? Not calling > irq_enter()/irq_exit() when we get an interrupt seems like a big problem. gic_handle_irq() calls handle_IRQ() which has the irq_enter()..irq_exit() wrappers. If we didn't have irq_exit(), then softirq's would be totally broken on all gic-based platforms.
=============================== [ 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: [<ffffffc00010206c>] irq_find_mapping+0x4c/0x198 </quote> As this issue is fairly widespread and involves at least three different architectures, a possible solution is to add a new handle_domain_irq entry point into the generic IRQ code that the interrupt controller code can call. This new function takes an irq_domain, and calls into irq_find_domain inside the irq_{enter,exit} block. An additional "lookup" parameter is used to allow non-domain architecture code to be replaced by this as well. Interrupt controllers can then be updated to use the new mechanism. This code is sitting behind a new CONFIG_HANDLE_DOMAIN_IRQ, as not all architectures implement set_irq_regs (yes, mn10300, I'm looking at you...). Reported-by: Vladimir Murzin <vladimir.murzin@arm.com> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> --- include/linux/irqdesc.h | 19 +++++++++++++++++++ kernel/irq/Kconfig | 3 +++ kernel/irq/irqdesc.c | 42 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 64 insertions(+) diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h index 472c021..ff24667 100644 --- a/include/linux/irqdesc.h +++ b/include/linux/irqdesc.h @@ -12,6 +12,8 @@ struct irq_affinity_notify; struct proc_dir_entry; struct module; struct irq_desc; +struct irq_domain; +struct pt_regs; /** * struct irq_desc - interrupt descriptor @@ -118,6 +120,23 @@ static inline void generic_handle_irq_desc(unsigned int irq, struct irq_desc *de int generic_handle_irq(unsigned int irq); +#ifdef CONFIG_HANDLE_DOMAIN_IRQ +/* + * Convert a HW interrupt number to a logical one using a IRQ domain, + * and handle the result interrupt number. Return -EINVAL if + * conversion failed. Providing a NULL domain indicates that the + * conversion has already been done. + */ +int __handle_domain_irq(struct irq_domain *domain, unsigned int hwirq, + bool lookup, struct pt_regs *regs); + +static inline int handle_domain_irq(struct irq_domain *domain, + unsigned int hwirq, struct pt_regs *regs) +{ + return __handle_domain_irq(domain, hwirq, true, regs); +} +#endif + /* Test to see if a driver has successfully requested an irq */ static inline int irq_has_action(unsigned int irq) { diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig index d269cec..225086b 100644 --- a/kernel/irq/Kconfig +++ b/kernel/irq/Kconfig @@ -55,6 +55,9 @@ config GENERIC_IRQ_CHIP config IRQ_DOMAIN bool +config HANDLE_DOMAIN_IRQ + bool + config IRQ_DOMAIN_DEBUG bool "Expose hardware/virtual IRQ mapping via debugfs" depends on IRQ_DOMAIN && DEBUG_FS diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c index 1487a12..a1782f8 100644 --- a/kernel/irq/irqdesc.c +++ b/kernel/irq/irqdesc.c @@ -14,6 +14,7 @@ #include <linux/kernel_stat.h> #include <linux/radix-tree.h> #include <linux/bitmap.h> +#include <linux/irqdomain.h> #include "internals.h" @@ -336,6 +337,47 @@ int generic_handle_irq(unsigned int irq) } EXPORT_SYMBOL_GPL(generic_handle_irq); +#ifdef CONFIG_HANDLE_DOMAIN_IRQ +/** + * __handle_domain_irq - Invoke the handler for a HW irq belonging to a domain + * @domain: The domain where to perform the lookup + * @hwirq: The HW irq number to convert to a logical one + * @lookup: Whether to perform the domain lookup or not + * @regs: Register file coming from the low-level handling code + * + * Returns: 0 on success, or -EINVAL if conversion has failed + */ +int __handle_domain_irq(struct irq_domain *domain, unsigned int hwirq, + bool lookup, struct pt_regs *regs) +{ + struct pt_regs *old_regs = set_irq_regs(regs); + unsigned int irq = hwirq; + int ret = 0; + + irq_enter(); + +#ifdef CONFIG_IRQ_DOMAIN + if (lookup) + irq = irq_find_mapping(domain, hwirq); +#endif + + /* + * Some hardware gives randomly wrong interrupts. Rather + * than crashing, do something sensible. + */ + if (unlikely(!irq || irq >= nr_irqs)) { + ack_bad_irq(irq); + ret = -EINVAL; + } else { + generic_handle_irq(irq); + } + + irq_exit(); + set_irq_regs(old_regs); + return ret; +} +#endif + /* Dynamic interrupt handling */ /**
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: <quote>