e02e68d31e
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>
172 lines
5.2 KiB
C
172 lines
5.2 KiB
C
/* thread_info.h: x86_64 low-level thread information
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*
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* Copyright (C) 2002 David Howells (dhowells@redhat.com)
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* - Incorporating suggestions made by Linus Torvalds and Dave Miller
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*/
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#ifndef _ASM_THREAD_INFO_H
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#define _ASM_THREAD_INFO_H
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#ifdef __KERNEL__
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#include <asm/page.h>
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#include <asm/types.h>
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#include <asm/pda.h>
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/*
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* low level task data that entry.S needs immediate access to
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* - this struct should fit entirely inside of one cache line
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* - this struct shares the supervisor stack pages
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*/
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#ifndef __ASSEMBLY__
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struct task_struct;
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struct exec_domain;
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#include <asm/mmsegment.h>
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struct thread_info {
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struct task_struct *task; /* main task structure */
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struct exec_domain *exec_domain; /* execution domain */
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__u32 flags; /* low level flags */
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__u32 status; /* thread synchronous flags */
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__u32 cpu; /* current CPU */
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int preempt_count; /* 0 => preemptable, <0 => BUG */
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mm_segment_t addr_limit;
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struct restart_block restart_block;
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};
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#endif
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/*
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* macros/functions for gaining access to the thread information structure
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* preempt_count needs to be 1 initially, until the scheduler is functional.
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*/
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#ifndef __ASSEMBLY__
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#define INIT_THREAD_INFO(tsk) \
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{ \
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.task = &tsk, \
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.exec_domain = &default_exec_domain, \
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.flags = 0, \
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.cpu = 0, \
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.preempt_count = 1, \
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.addr_limit = KERNEL_DS, \
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.restart_block = { \
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.fn = do_no_restart_syscall, \
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}, \
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}
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#define init_thread_info (init_thread_union.thread_info)
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#define init_stack (init_thread_union.stack)
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static inline struct thread_info *current_thread_info(void)
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{
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struct thread_info *ti;
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ti = (void *)(read_pda(kernelstack) + PDA_STACKOFFSET - THREAD_SIZE);
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return ti;
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}
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/* do not use in interrupt context */
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static inline struct thread_info *stack_thread_info(void)
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{
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struct thread_info *ti;
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__asm__("andq %%rsp,%0; ":"=r" (ti) : "0" (~(THREAD_SIZE - 1)));
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return ti;
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}
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/* thread information allocation */
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#ifdef CONFIG_DEBUG_STACK_USAGE
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#define alloc_thread_info(tsk) \
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({ \
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struct thread_info *ret; \
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\
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ret = ((struct thread_info *) __get_free_pages(GFP_KERNEL,THREAD_ORDER)); \
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if (ret) \
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memset(ret, 0, THREAD_SIZE); \
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ret; \
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})
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#else
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#define alloc_thread_info(tsk) \
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((struct thread_info *) __get_free_pages(GFP_KERNEL,THREAD_ORDER))
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#endif
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#define free_thread_info(ti) free_pages((unsigned long) (ti), THREAD_ORDER)
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#else /* !__ASSEMBLY__ */
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/* how to get the thread information struct from ASM */
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#define GET_THREAD_INFO(reg) \
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movq %gs:pda_kernelstack,reg ; \
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subq $(THREAD_SIZE-PDA_STACKOFFSET),reg
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#endif
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/*
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* thread information flags
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* - these are process state flags that various assembly files may need to access
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* - pending work-to-be-done flags are in LSW
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* - other flags in MSW
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* Warning: layout of LSW is hardcoded in entry.S
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*/
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#define TIF_SYSCALL_TRACE 0 /* syscall trace active */
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#define TIF_NOTIFY_RESUME 1 /* resumption notification requested */
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#define TIF_SIGPENDING 2 /* signal pending */
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#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
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#define TIF_SINGLESTEP 4 /* reenable singlestep on user return*/
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#define TIF_IRET 5 /* force IRET */
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#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
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#define TIF_SECCOMP 8 /* secure computing */
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#define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal */
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#define TIF_MCE_NOTIFY 10 /* notify userspace of an MCE */
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/* 16 free */
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#define TIF_IA32 17 /* 32bit process */
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#define TIF_FORK 18 /* ret_from_fork */
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#define TIF_ABI_PENDING 19
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#define TIF_MEMDIE 20
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#define TIF_DEBUG 21 /* uses debug registers */
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#define TIF_IO_BITMAP 22 /* uses I/O bitmap */
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#define TIF_FREEZE 23 /* is freezing for suspend */
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#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
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#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
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#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
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#define _TIF_SINGLESTEP (1<<TIF_SINGLESTEP)
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#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
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#define _TIF_IRET (1<<TIF_IRET)
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#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
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#define _TIF_SECCOMP (1<<TIF_SECCOMP)
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#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
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#define _TIF_MCE_NOTIFY (1<<TIF_MCE_NOTIFY)
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#define _TIF_IA32 (1<<TIF_IA32)
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#define _TIF_FORK (1<<TIF_FORK)
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#define _TIF_ABI_PENDING (1<<TIF_ABI_PENDING)
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#define _TIF_DEBUG (1<<TIF_DEBUG)
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#define _TIF_IO_BITMAP (1<<TIF_IO_BITMAP)
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#define _TIF_FREEZE (1<<TIF_FREEZE)
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/* work to do on interrupt/exception return */
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#define _TIF_WORK_MASK \
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(0x0000FFFF & ~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP|_TIF_SECCOMP))
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/* work to do on any return to user space */
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#define _TIF_ALLWORK_MASK (0x0000FFFF & ~_TIF_SECCOMP)
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/* flags to check in __switch_to() */
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#define _TIF_WORK_CTXSW (_TIF_DEBUG|_TIF_IO_BITMAP)
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#define PREEMPT_ACTIVE 0x10000000
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/*
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* Thread-synchronous status.
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*
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* This is different from the flags in that nobody else
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* ever touches our thread-synchronous status, so we don't
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* have to worry about atomic accesses.
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*/
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#define TS_USEDFPU 0x0001 /* FPU was used by this task this quantum (SMP) */
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#define TS_COMPAT 0x0002 /* 32bit syscall active */
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#define TS_POLLING 0x0004 /* true if in idle loop and not sleeping */
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#define tsk_is_polling(t) (task_thread_info(t)->status & TS_POLLING)
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#endif /* __KERNEL__ */
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#endif /* _ASM_THREAD_INFO_H */
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