Merge branch 'ras-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RAS fix from Ingo Molnar: "Fix an RCU warning that triggers when /dev/mcelog is used" * 'ras-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/mcelog: Get rid of RCU remnantszero-colors
Linus Torvalds
commit
b21172cf6d
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@ -24,14 +24,6 @@ static DEFINE_MUTEX(mce_chrdev_read_mutex);
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static char mce_helper[128];
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static char *mce_helper_argv[2] = { mce_helper, NULL };
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#define mce_log_get_idx_check(p) \
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({ \
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RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held() && \
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!lockdep_is_held(&mce_chrdev_read_mutex), \
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"suspicious mce_log_get_idx_check() usage"); \
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smp_load_acquire(&(p)); \
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})
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/*
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* Lockless MCE logging infrastructure.
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* This avoids deadlocks on printk locks without having to break locks. Also
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@ -53,43 +45,32 @@ static int dev_mce_log(struct notifier_block *nb, unsigned long val,
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void *data)
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{
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struct mce *mce = (struct mce *)data;
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unsigned int next, entry;
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unsigned int entry;
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wmb();
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for (;;) {
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entry = mce_log_get_idx_check(mcelog.next);
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for (;;) {
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mutex_lock(&mce_chrdev_read_mutex);
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/*
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* When the buffer fills up discard new entries.
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* Assume that the earlier errors are the more
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* interesting ones:
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*/
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if (entry >= MCE_LOG_LEN) {
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set_bit(MCE_OVERFLOW,
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(unsigned long *)&mcelog.flags);
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return NOTIFY_OK;
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}
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/* Old left over entry. Skip: */
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if (mcelog.entry[entry].finished) {
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entry++;
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continue;
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}
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break;
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}
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smp_rmb();
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next = entry + 1;
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if (cmpxchg(&mcelog.next, entry, next) == entry)
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break;
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entry = mcelog.next;
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/*
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* When the buffer fills up discard new entries. Assume that the
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* earlier errors are the more interesting ones:
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*/
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if (entry >= MCE_LOG_LEN) {
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set_bit(MCE_OVERFLOW, (unsigned long *)&mcelog.flags);
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goto unlock;
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}
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mcelog.next = entry + 1;
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memcpy(mcelog.entry + entry, mce, sizeof(struct mce));
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wmb();
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mcelog.entry[entry].finished = 1;
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wmb();
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/* wake processes polling /dev/mcelog */
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wake_up_interruptible(&mce_chrdev_wait);
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unlock:
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mutex_unlock(&mce_chrdev_read_mutex);
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return NOTIFY_OK;
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}
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@ -177,13 +158,6 @@ static int mce_chrdev_release(struct inode *inode, struct file *file)
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return 0;
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}
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static void collect_tscs(void *data)
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{
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unsigned long *cpu_tsc = (unsigned long *)data;
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cpu_tsc[smp_processor_id()] = rdtsc();
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}
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static int mce_apei_read_done;
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/* Collect MCE record of previous boot in persistent storage via APEI ERST. */
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@ -231,14 +205,9 @@ static ssize_t mce_chrdev_read(struct file *filp, char __user *ubuf,
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size_t usize, loff_t *off)
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{
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char __user *buf = ubuf;
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unsigned long *cpu_tsc;
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unsigned prev, next;
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unsigned next;
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int i, err;
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cpu_tsc = kmalloc(nr_cpu_ids * sizeof(long), GFP_KERNEL);
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if (!cpu_tsc)
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return -ENOMEM;
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mutex_lock(&mce_chrdev_read_mutex);
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if (!mce_apei_read_done) {
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@ -247,65 +216,29 @@ static ssize_t mce_chrdev_read(struct file *filp, char __user *ubuf,
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goto out;
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}
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next = mce_log_get_idx_check(mcelog.next);
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/* Only supports full reads right now */
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err = -EINVAL;
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if (*off != 0 || usize < MCE_LOG_LEN*sizeof(struct mce))
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goto out;
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next = mcelog.next;
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err = 0;
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prev = 0;
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do {
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for (i = prev; i < next; i++) {
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unsigned long start = jiffies;
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struct mce *m = &mcelog.entry[i];
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while (!m->finished) {
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if (time_after_eq(jiffies, start + 2)) {
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memset(m, 0, sizeof(*m));
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goto timeout;
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}
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cpu_relax();
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}
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smp_rmb();
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err |= copy_to_user(buf, m, sizeof(*m));
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buf += sizeof(*m);
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timeout:
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;
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}
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memset(mcelog.entry + prev, 0,
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(next - prev) * sizeof(struct mce));
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prev = next;
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next = cmpxchg(&mcelog.next, prev, 0);
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} while (next != prev);
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synchronize_sched();
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/*
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* Collect entries that were still getting written before the
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* synchronize.
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*/
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on_each_cpu(collect_tscs, cpu_tsc, 1);
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for (i = next; i < MCE_LOG_LEN; i++) {
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for (i = 0; i < next; i++) {
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struct mce *m = &mcelog.entry[i];
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if (m->finished && m->tsc < cpu_tsc[m->cpu]) {
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err |= copy_to_user(buf, m, sizeof(*m));
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smp_rmb();
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buf += sizeof(*m);
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memset(m, 0, sizeof(*m));
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}
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err |= copy_to_user(buf, m, sizeof(*m));
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buf += sizeof(*m);
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}
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memset(mcelog.entry, 0, next * sizeof(struct mce));
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mcelog.next = 0;
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if (err)
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err = -EFAULT;
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out:
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mutex_unlock(&mce_chrdev_read_mutex);
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kfree(cpu_tsc);
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return err ? err : buf - ubuf;
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}
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