diff options
author | Tim Hockin <thockin@google.com> | 2007-07-21 15:10:36 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-07-22 01:37:10 (GMT) |
commit | e02e68d31e2d436197386997727b216fee9c4623 (patch) | |
tree | 97160f82b8deaf6e83d988844d5b410baa4e3ab4 /include | |
parent | f528e7ba28492e363a64c80c414ded4cadf48f89 (diff) | |
download | linux-fsl-qoriq-e02e68d31e2d436197386997727b216fee9c4623.tar.xz |
x86_64: support poll() on /dev/mcelog
Background:
/dev/mcelog is typically polled manually. This is less than optimal for
situations where accurate accounting of MCEs is important. Calling
poll() on /dev/mcelog does not work.
Description:
This patch adds support for poll() to /dev/mcelog. This results in
immediate wakeup of user apps whenever the poller finds MCEs. Because
the exception handler can not take any locks, it can not call the wakeup
itself. Instead, it uses a thread_info flag (TIF_MCE_NOTIFY) which is
caught at the next return from interrupt or exit from idle, calling the
mce_user_notify() routine. This patch also disables the "fake panic"
path of the mce_panic(), because it results in printk()s in the exception
handler and crashy systems.
This patch also does some small cleanup for essentially unused variables,
and moves the user notification into the body of the poller, so it is
only called once per poll, rather than once per CPU.
Result:
Applications can now poll() on /dev/mcelog. When an error is logged
(whether through the poller or through an exception) the applications are
woken up promptly. This should not affect any previous behaviors. If no
MCEs are being logged, there is no overhead.
Alternatives:
I considered simply supporting poll() through the poller and not using
TIF_MCE_NOTIFY at all. However, the time between an uncorrectable error
happening and the user application being notified is *the*most* critical
window for us. Many uncorrectable errors can be logged to the network if
given a chance.
I also considered doing the MCE poll directly from the idle notifier, but
decided that was overkill.
Testing:
I used an error-injecting DIMM to create lots of correctable DRAM errors
and verified that my user app is woken up in sync with the polling interval.
I also used the northbridge to inject uncorrectable ECC errors, and
verified (printk() to the rescue) that the notify routine is called and the
user app does wake up. I built with PREEMPT on and off, and verified
that my machine survives MCEs.
[wli@holomorphy.com: build fix]
Signed-off-by: Tim Hockin <thockin@google.com>
Signed-off-by: William Irwin <bill.irwin@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r-- | include/asm-x86_64/mce.h | 2 | ||||
-rw-r--r-- | include/asm-x86_64/thread_info.h | 2 |
2 files changed, 4 insertions, 0 deletions
diff --git a/include/asm-x86_64/mce.h b/include/asm-x86_64/mce.h index 177e92b..556be55 100644 --- a/include/asm-x86_64/mce.h +++ b/include/asm-x86_64/mce.h @@ -105,6 +105,8 @@ extern atomic_t mce_entry; extern void do_machine_check(struct pt_regs *, long); +extern int mce_notify_user(void); + #endif #endif diff --git a/include/asm-x86_64/thread_info.h b/include/asm-x86_64/thread_info.h index 10bb5a8..33c72ef 100644 --- a/include/asm-x86_64/thread_info.h +++ b/include/asm-x86_64/thread_info.h @@ -115,6 +115,7 @@ static inline struct thread_info *stack_thread_info(void) #define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */ #define TIF_SECCOMP 8 /* secure computing */ #define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal */ +#define TIF_MCE_NOTIFY 10 /* notify userspace of an MCE */ /* 16 free */ #define TIF_IA32 17 /* 32bit process */ #define TIF_FORK 18 /* ret_from_fork */ @@ -133,6 +134,7 @@ static inline struct thread_info *stack_thread_info(void) #define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT) #define _TIF_SECCOMP (1<<TIF_SECCOMP) #define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK) +#define _TIF_MCE_NOTIFY (1<<TIF_MCE_NOTIFY) #define _TIF_IA32 (1<<TIF_IA32) #define _TIF_FORK (1<<TIF_FORK) #define _TIF_ABI_PENDING (1<<TIF_ABI_PENDING) |