Commit 403a91b1 authored by Jiri Kosina's avatar Jiri Kosina Committed by Tejun Heo
Browse files

percpu: allow pcpu_alloc() to be called with IRQs off 



pcpu_alloc() and pcpu_extend_area_map() perform a series of
spin_lock_irq()/spin_unlock_irq() calls, which make them unsafe
with respect to being called from contexts which have IRQs off.

This patch converts the code to perform save/restore of flags instead,
making pcpu_alloc() (or __alloc_percpu() respectively) to be called
from early kernel startup stage, where IRQs are off.

This is needed for proper initialization of per-cpu rq_weight data from
sched_init().

tj: added comment explaining why irqsave/restore is used in alloc path.

Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 1a0c3298

mm/percpu.c

+17 −13
Original line number Diff line number Diff line
@@ -153,7 +153,10 @@ static int pcpu_reserved_chunk_limit; 
 *

 * During allocation, pcpu_alloc_mutex is kept locked all the time and

 * pcpu_lock is grabbed and released as necessary.  All actual memory

 * allocations are done using GFP_KERNEL with pcpu_lock released.

 * allocations are done using GFP_KERNEL with pcpu_lock released.  In

 * general, percpu memory can't be allocated with irq off but

 * irqsave/restore are still used in alloc path so that it can be used

 * from early init path - sched_init() specifically.

 *

 * Free path accesses and alters only the index data structures, so it

 * can be safely called from atomic context.  When memory needs to be
@@ -366,7 +369,7 @@ static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr) 
 * RETURNS:

 * 0 if noop, 1 if successfully extended, -errno on failure.

 */

static int pcpu_extend_area_map(struct pcpu_chunk *chunk)

static int pcpu_extend_area_map(struct pcpu_chunk *chunk, unsigned long *flags)

{

	int new_alloc;

	int *new;
@@ -376,7 +379,7 @@ static int pcpu_extend_area_map(struct pcpu_chunk *chunk) 
	if (chunk->map_alloc >= chunk->map_used + 2)

		return 0;



	spin_unlock_irq(&pcpu_lock);

	spin_unlock_irqrestore(&pcpu_lock, *flags);



	new_alloc = PCPU_DFL_MAP_ALLOC;

	while (new_alloc < chunk->map_used + 2)
@@ -384,7 +387,7 @@ static int pcpu_extend_area_map(struct pcpu_chunk *chunk) 


	new = pcpu_mem_alloc(new_alloc * sizeof(new[0]));

	if (!new) {

		spin_lock_irq(&pcpu_lock);

		spin_lock_irqsave(&pcpu_lock, *flags);

		return -ENOMEM;

	}
@@ -393,7 +396,7 @@ static int pcpu_extend_area_map(struct pcpu_chunk *chunk) 
	 * could have happened inbetween, so map_used couldn't have

	 * grown.

	 */

	spin_lock_irq(&pcpu_lock);

	spin_lock_irqsave(&pcpu_lock, *flags);

	BUG_ON(new_alloc < chunk->map_used + 2);



	size = chunk->map_alloc * sizeof(chunk->map[0]);
@@ -1047,6 +1050,7 @@ static void *pcpu_alloc(size_t size, size_t align, bool reserved) 
	struct pcpu_chunk *chunk;

	const char *err;

	int slot, off;

	unsigned long flags;



	if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE)) {

		WARN(true, "illegal size (%zu) or align (%zu) for "
@@ -1055,13 +1059,13 @@ static void *pcpu_alloc(size_t size, size_t align, bool reserved) 
	}



	mutex_lock(&pcpu_alloc_mutex);

	spin_lock_irq(&pcpu_lock);

	spin_lock_irqsave(&pcpu_lock, flags);



	/* serve reserved allocations from the reserved chunk if available */

	if (reserved && pcpu_reserved_chunk) {

		chunk = pcpu_reserved_chunk;

		if (size > chunk->contig_hint ||

		    pcpu_extend_area_map(chunk) < 0) {

		    pcpu_extend_area_map(chunk, &flags) < 0) {

			err = "failed to extend area map of reserved chunk";

			goto fail_unlock;

		}
@@ -1079,7 +1083,7 @@ restart: 
			if (size > chunk->contig_hint)

				continue;



			switch (pcpu_extend_area_map(chunk)) {

			switch (pcpu_extend_area_map(chunk, &flags)) {

			case 0:

				break;

			case 1:
@@ -1096,7 +1100,7 @@ restart: 
	}



	/* hmmm... no space left, create a new chunk */

	spin_unlock_irq(&pcpu_lock);

	spin_unlock_irqrestore(&pcpu_lock, flags);



	chunk = alloc_pcpu_chunk();

	if (!chunk) {
@@ -1104,16 +1108,16 @@ restart: 
		goto fail_unlock_mutex;

	}



	spin_lock_irq(&pcpu_lock);

	spin_lock_irqsave(&pcpu_lock, flags);

	pcpu_chunk_relocate(chunk, -1);

	goto restart;



area_found:

	spin_unlock_irq(&pcpu_lock);

	spin_unlock_irqrestore(&pcpu_lock, flags);



	/* populate, map and clear the area */

	if (pcpu_populate_chunk(chunk, off, size)) {

		spin_lock_irq(&pcpu_lock);

		spin_lock_irqsave(&pcpu_lock, flags);

		pcpu_free_area(chunk, off);

		err = "failed to populate";

		goto fail_unlock;
@@ -1125,7 +1129,7 @@ area_found: 
	return __addr_to_pcpu_ptr(chunk->base_addr + off);



fail_unlock:

	spin_unlock_irq(&pcpu_lock);

	spin_unlock_irqrestore(&pcpu_lock, flags);

fail_unlock_mutex:

	mutex_unlock(&pcpu_alloc_mutex);

	if (warn_limit) {

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