mm/memblock: disable local irqs while late memblock changes

There is a possibility of deadlock while doing late
memblock configuration as only preemption is disabled and
irq can be serviced while seqlock is held and in turn
memblock_is_memory can be called from irq context thus
trying to claim seqlock again. Following call stack was
observed,

[<c02136d4>] memblock_search+0x1c
[<c021487c>] memblock_is_memory+0x10
[<c01e4684>] free_kmem_pages+0x44
[<c0121c04>] free_task+0x28
[<c0178b30>] rcu_process_callbacks+0x488
[<c0127e30>] __do_softirq+0x150
[<c0128284>] irq_exit+0x84
[<c010c11c>] handle_IPI+0x12c
[<c0100588>] gic_handle_irq+0x70
[<c0e9efc0>] __irq_svc+0x40
[<c0214a8c>] memblock_region_resize_late_end+0xc
[<c057010c>] removed_alloc+0x110
[<c04ab2c4>] pil_boot+0x2b0
[<c04b7700>] __subsystem_get+0xe0
[<c04b79cc>] subsys_device_open+0x74
[<c0229f20>] chrdev_open+0x12c
[<c02246e4>] do_dentry_open+0x280
[<c0232698>] do_last+0x9a4
[<c0232b8c>] path_openat+0x23c
[<c0233bf0>] do_filp_open+0x2c

Fix it by disabling irqs during late memblock
configuration. It is a one time operation which changes
memblock related data structures and doesn't carry
performance impact.

CRs-Fixed: 1003890
Change-Id: I3ff1894f0c80580920b1971cda357915665b5054
Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>

3 files changed, 16 insertions, 9 deletions

diff --git a/drivers/base/dma-removed.c b/drivers/base/dma-removed.c
index 4482deaab0f2..87c743995a50 100644
--- a/drivers/base/dma-removed.c
+++ b/drivers/base/dma-removed.c
@@ -181,15 +181,16 @@ static void removed_region_fixup(struct removed_region *dma_mem, int index)
 {
 	unsigned long fixup_size;
 	unsigned long base_pfn;
+	unsigned long flags;
 
 	if (index > dma_mem->nr_pages)
 		return;
 
 	/* carve-out */
-	memblock_region_resize_late_begin();
+	flags = memblock_region_resize_late_begin();
 	memblock_free(dma_mem->base, dma_mem->nr_pages * PAGE_SIZE);
 	memblock_remove(dma_mem->base, index * PAGE_SIZE);
-	memblock_region_resize_late_end();
+	memblock_region_resize_late_end(flags);
 
 	/* clear page-mappings */
 	base_pfn = dma_mem->base >> PAGE_SHIFT;
diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index 42b40345119f..3d28c3a18b95 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -83,8 +83,8 @@ int memblock_mark_hotplug(phys_addr_t base, phys_addr_t size);
 int memblock_clear_hotplug(phys_addr_t base, phys_addr_t size);
 int memblock_mark_mirror(phys_addr_t base, phys_addr_t size);
 ulong choose_memblock_flags(void);
-void memblock_region_resize_late_begin(void);
-void memblock_region_resize_late_end(void);
+unsigned long memblock_region_resize_late_begin(void);
+void memblock_region_resize_late_end(unsigned long);
 
 /* Low level functions */
 int memblock_add_range(struct memblock_type *type,
diff --git a/mm/memblock.c b/mm/memblock.c
index bdeb22faafff..7f0a860a357e 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -21,6 +21,7 @@
 #include <linux/memblock.h>
 #include <linux/preempt.h>
 #include <linux/seqlock.h>
+#include <linux/irqflags.h>
 
 #include <asm-generic/sections.h>
 #include <linux/io.h>
@@ -1675,30 +1676,35 @@ void __init memblock_allow_resize(void)
 	memblock_can_resize = 1;
 }
 
-static void __init_memblock memblock_resize_late(int begin)
+static unsigned long __init_memblock
+memblock_resize_late(int begin, unsigned long flags)
 {
 	static int memblock_can_resize_old;
 
 	if (begin) {
 		preempt_disable();
+		local_irq_save(flags);
 		memblock_can_resize_old = memblock_can_resize;
 		memblock_can_resize = 0;
 		raw_write_seqcount_begin(&memblock_seq);
 	} else {
 		raw_write_seqcount_end(&memblock_seq);
 		memblock_can_resize = memblock_can_resize_old;
+		local_irq_restore(flags);
 		preempt_enable();
 	}
+
+	return flags;
 }
 
-void __init_memblock memblock_region_resize_late_begin(void)
+unsigned long __init_memblock memblock_region_resize_late_begin(void)
 {
-	memblock_resize_late(1);
+	return memblock_resize_late(1, 0);
 }
 
-void __init_memblock memblock_region_resize_late_end(void)
+void __init_memblock memblock_region_resize_late_end(unsigned long flags)
 {
-	memblock_resize_late(0);
+	memblock_resize_late(0, flags);
 }
 
 static int __init early_memblock(char *p)