3 files changed, 30 insertions, 8 deletions
diff --git a/kernel/kexec.c b/kernel/kexec.c
index 0b49a0a58102..2bee072268d9 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -64,7 +64,9 @@ bool kexec_in_progress = false;
 char __weak kexec_purgatory[0];
 size_t __weak kexec_purgatory_size = 0;
+#ifdef CONFIG_KEXEC_FILE
 static int kexec_calculate_store_digests(struct kimage *image);
+#endif
 /* Location of the reserved area for the crash kernel */
 struct resource crashk_res = {
@@ -341,6 +343,7 @@ out_free_image:
        return ret;
 }
+#ifdef CONFIG_KEXEC_FILE
 static int copy_file_from_fd(int fd, void **buf, unsigned long *buf_len)
 {
        struct fd f = fdget(fd);
@@ -612,6 +615,9 @@ out_free_image:
        kfree(image);
        return ret;
 }
+#else /* CONFIG_KEXEC_FILE */
+static inline void kimage_file_post_load_cleanup(struct kimage *image) { }
+#endif /* CONFIG_KEXEC_FILE */
 static int kimage_is_destination_range(struct kimage *image,
                                        unsigned long start,
@@ -1375,6 +1381,7 @@ COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
 }
 #endif
+#ifdef CONFIG_KEXEC_FILE
 SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
                unsigned long, cmdline_len, const char __user *, cmdline_ptr,
                unsigned long, flags)
@@ -1451,6 +1458,8 @@ out:
        return ret;
 }
+#endif /* CONFIG_KEXEC_FILE */
 void crash_kexec(struct pt_regs *regs)
 {
        /* Take the kexec_mutex here to prevent sys_kexec_load
@@ -2006,6 +2015,7 @@ static int __init crash_save_vmcoreinfo_init(void)
 subsys_initcall(crash_save_vmcoreinfo_init);
+#ifdef CONFIG_KEXEC_FILE
 static int __kexec_add_segment(struct kimage *image, char *buf,
                               unsigned long bufsz, unsigned long mem,
                               unsigned long memsz)
@@ -2682,6 +2692,7 @@ int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name,
        return 0;
 }
+#endif /* CONFIG_KEXEC_FILE */
 /*
 * Move into place and start executing a preloaded standalone
diff --git a/kernel/resource.c b/kernel/resource.c
index da14b8d09296..60c5a3856ab7 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -351,15 +351,12 @@ static int find_next_iomem_res(struct resource *res, char *name,
        end = res->end;
        BUG_ON(start >= end);
-        read_lock(&resource_lock);
+        if (first_level_children_only)
-        if (first_level_children_only) {
-                p = iomem_resource.child;
                sibling_only = true;
-        } else
-                p = &iomem_resource;
-        while ((p = next_resource(p, sibling_only))) {
+        read_lock(&resource_lock);
+        for (p = iomem_resource.child; p; p = next_resource(p, sibling_only)) {
                if (p->flags != res->flags)
                        continue;
                if (name && strcmp(p->name, name))
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index afb04b9b818a..b38fb2b9e237 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -626,8 +626,22 @@ int ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
                work = &cpu_buffer->irq_work;
        }
-        work->waiters_pending = true;
        poll_wait(filp, &work->waiters, poll_table);
+        work->waiters_pending = true;
+        /*
+         * There's a tight race between setting the waiters_pending and
+         * checking if the ring buffer is empty.  Once the waiters_pending bit
+         * is set, the next event will wake the task up, but we can get stuck
+         * if there's only a single event in.
+         *
+         * FIXME: Ideally, we need a memory barrier on the writer side as well,
+         * but adding a memory barrier to all events will cause too much of a
+         * performance hit in the fast path.  We only need a memory barrier when
+         * the buffer goes from empty to having content.  But as this race is
+         * extremely small, and it's not a problem if another event comes in, we
+         * will fix it later.
+         */
+        smp_mb();
        if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
            (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))