Jan Kiszka wrote: > ... > This patch is an RFC as the following issues need to be resolved: > > o The might be parts of I-pipe remaining that make use of > preemp_disable even over non-root contexts. Philippe indicated the > PPC PIC code would be one example.
Mmpf, first test, then post. Looks like there are more subtle scenarios hidden: > <3>[ 121.256585] I-pipe: Detected illicit call from domain 'Xenomai' > <4>[ 121.256616] into a service reserved for domain 'Linux' and > below. > <4>[ 121.256695] I-pipe tracer log (30 points): > <4>[ 121.256729] func 0 ipipe_trace_panic_freeze+0x8 > (ipipe_check_context+0x36) > <4>[ 121.256863] func -1 ipipe_check_context+0x9 > (__switch_to+0x34) > <4>[ 121.256951] func -2 __switch_to+0xe > (xnpod_schedule+0x69b) > <4>[ 121.257039] [ 79] gatekee -1 -16 xnpod_schedule+0x84 > (xnintr_irq_handler+0xa1) > <4>[ 121.257129] func -19 xnpod_schedule+0xe > (xnintr_irq_handler+0xa1) > <4>[ 121.257213] [ 868] Odometr 19 -26 xnpod_resume_thread+0x48 > (xnthread_timeout_handler+0x21) > <4>[ 121.257448] func -28 xnpod_resume_thread+0xe > (xnthread_timeout_handler+0x21) > <4>[ 121.257607] func -30 xnthread_timeout_handler+0x8 > (xntimer_do_tick_aperiodic+0x7b) > <4>[ 121.257779] func -33 xntimer_do_tick_aperiodic+0xe > (xnpod_announce_tick+0x17) > <4>[ 121.257948] func -34 xnpod_announce_tick+0xa > (xnintr_irq_handler+0x2a) Namely, __switch_to->__unlazy_fpu->save_init_fpu->preempt_disable. Philippe, looks like killing the ipipe_preempt_guard is not trivial... Anyway, attached version 2 of this patch enables both stack dump and ipipe-backtrace. Jan
---
arch/i386/kernel/ipipe-root.c | 9 ++++++---
include/linux/ipipe.h | 6 ++++++
include/linux/kernel.h | 16 ++++++++++++++--
include/linux/preempt.h | 11 ++++++++++-
kernel/ipipe/Kconfig.debug | 9 +++++++++
kernel/ipipe/generic.c | 31 +++++++++++++++++++++++++++++++
6 files changed, 76 insertions(+), 6 deletions(-)
Index: linux-2.6.17.13/include/linux/ipipe.h
===================================================================
--- linux-2.6.17.13.orig/include/linux/ipipe.h
+++ linux-2.6.17.13/include/linux/ipipe.h
@@ -694,6 +694,12 @@ int fastcall ipipe_set_ptd(int key,
void fastcall *ipipe_get_ptd(int key);
+#ifdef CONFIG_IPIPE_DEBUG_CONTEXT
+void fastcall ipipe_check_context(struct ipipe_domain *border_ipd);
+#else /* !CONFIG_IPIPE_DEBUG_CONTEXT */
+#define ipipe_check_context(border_ipd) do { } while (0)
+#endif /* CONFIG_IPIPE_DEBUG_CONTEXT */
+
#define local_irq_enable_hw_cond() local_irq_enable_hw()
#define local_irq_disable_hw_cond() local_irq_disable_hw()
#define local_irq_save_hw_cond(flags) local_irq_save_hw(flags)
Index: linux-2.6.17.13/kernel/ipipe/Kconfig.debug
===================================================================
--- linux-2.6.17.13.orig/kernel/ipipe/Kconfig.debug
+++ linux-2.6.17.13/kernel/ipipe/Kconfig.debug
@@ -2,6 +2,15 @@ config IPIPE_DEBUG
bool "I-pipe debugging"
depends on IPIPE
+config IPIPE_DEBUG_CONTEXT
+ bool "Check for illicit cross-domain calls"
+ depends on IPIPE_DEBUG
+ ---help---
+ Enable this feature to arm checkpoints in the kernel that
+ verify the correct invocation context. On entry of critical
+ Linux services a warning is issued if the caller is not
+ running over the root domain.
+
config IPIPE_TRACE
bool "Latency tracing"
depends on IPIPE_DEBUG
Index: linux-2.6.17.13/kernel/ipipe/generic.c
===================================================================
--- linux-2.6.17.13.orig/kernel/ipipe/generic.c
+++ linux-2.6.17.13/kernel/ipipe/generic.c
@@ -29,6 +29,9 @@
#ifdef CONFIG_PROC_FS
#include <linux/proc_fs.h>
#endif /* CONFIG_PROC_FS */
+#ifdef CONFIG_IPIPE_TRACE_MCOUNT
+#include <linux/ipipe_trace.h>
+#endif /* CONFIG_IPIPE_TRACE_MCOUNT */
MODULE_DESCRIPTION("I-pipe");
MODULE_LICENSE("GPL");
@@ -410,6 +413,34 @@ void fastcall *ipipe_get_ptd (int key)
return current->ptd[key];
}
+#ifdef CONFIG_IPIPE_DEBUG_CONTEXT
+void fastcall ipipe_check_context(struct ipipe_domain *border_ipd)
+{
+ static int check_hit;
+
+ if (likely(ipipe_current_domain->priority <= border_ipd->priority) ||
+ check_hit)
+ return;
+
+ check_hit = 1;
+
+#ifdef CONFIG_IPIPE_TRACE_MCOUNT
+ ipipe_trace_panic_freeze();
+#endif /* CONFIG_IPIPE_TRACE_MCOUNT */
+ ipipe_set_printk_sync(ipipe_current_domain);
+ printk(KERN_ERR "I-pipe: Detected illicit call from domain '%s'\n"
+ KERN_ERR " into a service reserved for domain '%s' and "
+ "below.\n",
+ ipipe_current_domain->name, border_ipd->name);
+ show_stack(NULL, NULL);
+#ifdef CONFIG_IPIPE_TRACE_MCOUNT
+ ipipe_trace_panic_dump();
+#endif /* CONFIG_IPIPE_TRACE_MCOUNT */
+}
+
+EXPORT_SYMBOL(ipipe_check_context);
+#endif /* CONFIG_IPIPE_DEBUG_CONTEXT */
+
EXPORT_SYMBOL(ipipe_register_domain);
EXPORT_SYMBOL(ipipe_unregister_domain);
EXPORT_SYMBOL(ipipe_free_virq);
Index: linux-2.6.17.13/include/linux/kernel.h
===================================================================
--- linux-2.6.17.13.orig/include/linux/kernel.h
+++ linux-2.6.17.13/include/linux/kernel.h
@@ -60,11 +60,23 @@ struct user;
* be biten later when the calling function happens to sleep when it is not
* supposed to.
*/
+
+/* FIXME: This is ugly... */
+extern struct ipipe_domain ipipe_root;
+#ifdef CONFIG_IPIPE_DEBUG_CONTEXT
+void fastcall ipipe_check_context(struct ipipe_domain *border_ipd);
+#else /* !CONFIG_IPIPE_DEBUG_CONTEXT */
+#define ipipe_check_context(border_ipd) do { } while (0)
+#endif /* CONFIG_IPIPE_DEBUG_CONTEXT */
+
#ifdef CONFIG_PREEMPT_VOLUNTARY
extern int cond_resched(void);
-# define might_resched() cond_resched()
+# define might_resched() do { \
+ ipipe_check_context(&ipipe_root); \
+ cond_resched(); \
+ } while (0)
#else
-# define might_resched() do { } while (0)
+# define might_resched() ipipe_check_context(&ipipe_root)
#endif
#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
Index: linux-2.6.17.13/include/linux/preempt.h
===================================================================
--- linux-2.6.17.13.orig/include/linux/preempt.h
+++ linux-2.6.17.13/include/linux/preempt.h
@@ -23,6 +23,14 @@
#define preempt_count() (current_thread_info()->preempt_count)
+/* FIXME: This is ugly... */
+extern struct ipipe_domain ipipe_root;
+#ifdef CONFIG_IPIPE_DEBUG_CONTEXT
+void fastcall ipipe_check_context(struct ipipe_domain *border_ipd);
+#else /* !CONFIG_IPIPE_DEBUG_CONTEXT */
+#define ipipe_check_context(border_ipd) do { } while (0)
+#endif /* CONFIG_IPIPE_DEBUG_CONTEXT */
+
#ifdef CONFIG_PREEMPT
asmlinkage void preempt_schedule(void);
@@ -38,6 +46,7 @@ extern struct ipipe_domain ipipe_root;
#define preempt_disable() \
do { \
+ ipipe_check_context(&ipipe_root); \
if (ipipe_preempt_guard()) { \
inc_preempt_count(); \
barrier(); \
@@ -69,7 +78,7 @@ do {
\
#else
-#define preempt_disable() do { } while (0)
+#define preempt_disable() ipipe_check_context(&ipipe_root)
#define preempt_enable_no_resched() do { } while (0)
#define preempt_enable() do { } while (0)
#define preempt_check_resched() do { } while (0)
Index: linux-2.6.17.13/arch/i386/kernel/ipipe-root.c
===================================================================
--- linux-2.6.17.13.orig/arch/i386/kernel/ipipe-root.c
+++ linux-2.6.17.13/arch/i386/kernel/ipipe-root.c
@@ -70,9 +70,12 @@ static int __ipipe_ack_common_irq(unsign
ipipe_load_cpuid(); /* hw interrupts are off. */
flags = ipipe_test_and_stall_pipeline();
- preempt_disable();
- desc->handler->ack(irq);
- preempt_enable_no_resched();
+ if (ipipe_percpu_domain[cpuid] == ipipe_root_domain) {
+ preempt_disable();
+ desc->handler->ack(irq);
+ preempt_enable_no_resched();
+ } else
+ desc->handler->ack(irq);
ipipe_restore_pipeline_nosync(ipipe_percpu_domain[cpuid], flags, cpuid);
return 1;
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