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    Subject[PATCH 03/10] x86, mce: change writer timeout in mce_read
    Changed to use ndelay().

    (This piece originates from Huang's patch, titled:
    "x86, MCE: Fix bugs and issues of MCE log ring buffer")

    Originally-From: Huang Ying <ying.huang@intel.com>
    Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
    ---
    arch/x86/kernel/cpu/mcheck/mce.c | 11 ++++++++---
    1 files changed, 8 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
    index 2d0f9d8..9e8eabd 100644
    --- a/arch/x86/kernel/cpu/mcheck/mce.c
    +++ b/arch/x86/kernel/cpu/mcheck/mce.c
    @@ -52,6 +52,9 @@ int mce_disabled __read_mostly;

    #define SPINUNIT 100 /* 100ns */

    +/* Timeout log reader to wait writer to finish */
    +#define WRITER_TIMEOUT_NS NSEC_PER_MSEC
    +
    atomic_t mce_entry;

    DEFINE_PER_CPU(unsigned, mce_exception_count);
    @@ -1469,15 +1472,17 @@ static ssize_t mce_read(struct file *filp, char __user *ubuf, size_t usize,
    prev = 0;
    do {
    for (i = prev; i < next; i++) {
    - unsigned long start = jiffies;
    + int timeout = WRITER_TIMEOUT_NS;

    while (!mcelog.entry[i].finished) {
    - if (time_after_eq(jiffies, start + 2)) {
    + if (timeout-- <= 0) {
    memset(mcelog.entry + i, 0,
    sizeof(struct mce));
    + printk(KERN_WARNING "mcelog: timeout "
    + "waiting for writer to finish!\n");
    goto timeout;
    }
    - cpu_relax();
    + ndelay(1);
    }
    smp_rmb();
    err |= copy_to_user(buf, mcelog.entry + i,
    --
    1.6.4.3



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