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Message-Id: <4de043641213294e72@agluck-desktop.sc.intel.com>
Date: Fri, 27 May 2011 17:35:48 -0700
From: "Luck, Tony" <tony.luck@...el.com>
To: "Ingo Molnar" <mingo@...e.hu>, avi@...hat.com
Cc: linux-kernel@...r.kernel.org
Subject: [POC] mce: replace TIF_MCE_NOTIFY with TIF_USER_RETURN_NOTIFY
[Oops - forgot to Cc: LKML!]
Ingo wrote:
> We already have a generic facility to do such things at
> return-to-userspace: _TIF_USER_RETURN_NOTIFY.
This is what it might look like if we replaced the current use
of TIF_MCE_NOTIFY with TIF_USER_RETURN_NOTIFY in mce.c
Question: the notifier can potentially send signals to the current
process - so should the check for _TIF_USER_RETURN_NOTIFY in do_notify_resume
be moved before the check for _TIF_SIGPENDING? Would doing do be a problem
for the existing user of user-return-notifiers (kvm)?
Note1 - this is a backport of a version that I wrote and tested on
top of my mce-recovery patch set - since I had a debug environment
set up to test it there ... the backport was relatively painless,
but this version has only been compile tested.
Note2 - I didn't delete the TIF_MCE_NOTIFY definition - I'd like
to keep bit 10 available for a _TIF_USER_RETURN_NOTIFY_TASK feature
that would be run in the context of a specific task (on any cpu)
rather than on a specific cpu (in any task context).
-Tony
---
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index cc6c53a..054e127 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -845,6 +845,7 @@ config X86_REROUTE_FOR_BROKEN_BOOT_IRQS
config X86_MCE
bool "Machine Check / overheating reporting"
+ select USER_RETURN_NOTIFIER
---help---
Machine Check support allows the processor to notify the
kernel if it detects a problem (e.g. overheating, data corruption).
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 3385ea2..10b3dbe 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -38,6 +38,7 @@
#include <linux/mm.h>
#include <linux/debugfs.h>
#include <linux/edac_mce.h>
+#include <linux/user-return-notifier.h>
#include <asm/processor.h>
#include <asm/hw_irq.h>
@@ -69,6 +70,15 @@ atomic_t mce_entry;
DEFINE_PER_CPU(unsigned, mce_exception_count);
+struct mce_notify {
+ struct user_return_notifier urn;
+ bool registered;
+};
+
+static void mce_do_notify(struct user_return_notifier *urn);
+
+static DEFINE_PER_CPU(struct mce_notify, mce_notify);
+
/*
* Tolerant levels:
* 0: always panic on uncorrected errors, log corrected errors
@@ -923,6 +933,7 @@ void do_machine_check(struct pt_regs *regs, long error_code)
int i;
int worst = 0;
int severity;
+ struct mce_notify *np;
/*
* Establish sequential order between the CPUs entering the machine
* check handler.
@@ -1077,7 +1088,12 @@ void do_machine_check(struct pt_regs *regs, long error_code)
force_sig(SIGBUS, current);
/* notify userspace ASAP */
- set_thread_flag(TIF_MCE_NOTIFY);
+ np = &__get_cpu_var(mce_notify);
+ if (np->registered == 0) {
+ np->urn.on_user_return = mce_do_notify;
+ user_return_notifier_register(&np->urn);
+ np->registered = 1;
+ }
if (worst > 0)
mce_report_event(regs);
@@ -1094,28 +1110,35 @@ void __attribute__((weak)) memory_failure(unsigned long pfn, int vector)
printk(KERN_ERR "Action optional memory failure at %lx ignored\n", pfn);
}
+void mce_process_ring(void)
+{
+ unsigned long pfn;
+
+ mce_notify_irq();
+ while (mce_ring_get(&pfn))
+ memory_failure(pfn, MCE_VECTOR);
+}
+
/*
* Called after mce notification in process context. This code
* is allowed to sleep. Call the high level VM handler to process
* any corrupted pages.
* Assume that the work queue code only calls this one at a time
* per CPU.
- * Note we don't disable preemption, so this code might run on the wrong
- * CPU. In this case the event is picked up by the scheduled work queue.
- * This is merely a fast path to expedite processing in some common
- * cases.
*/
-void mce_notify_process(void)
+static void mce_do_notify(struct user_return_notifier *urn)
{
- unsigned long pfn;
- mce_notify_irq();
- while (mce_ring_get(&pfn))
- memory_failure(pfn, MCE_VECTOR);
+ struct mce_notify *np = container_of(urn, struct mce_notify, urn);
+
+ user_return_notifier_unregister(urn);
+ np->registered = 0;
+
+ mce_process_ring();
}
static void mce_process_work(struct work_struct *dummy)
{
- mce_notify_process();
+ mce_process_ring();
}
#ifdef CONFIG_X86_MCE_INTEL
@@ -1196,8 +1219,6 @@ int mce_notify_irq(void)
/* Not more than two messages every minute */
static DEFINE_RATELIMIT_STATE(ratelimit, 60*HZ, 2);
- clear_thread_flag(TIF_MCE_NOTIFY);
-
if (test_and_clear_bit(0, &mce_need_notify)) {
wake_up_interruptible(&mce_wait);
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 4fd173c..44efc22 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -838,12 +838,6 @@ static void do_signal(struct pt_regs *regs)
void
do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
{
-#ifdef CONFIG_X86_MCE
- /* notify userspace of pending MCEs */
- if (thread_info_flags & _TIF_MCE_NOTIFY)
- mce_notify_process();
-#endif /* CONFIG_X86_64 && CONFIG_X86_MCE */
-
/* deal with pending signal delivery */
if (thread_info_flags & _TIF_SIGPENDING)
do_signal(regs);
--
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