From: Kent Overstreet <k...@daterainc.com>
This patch changes percpu_ida_alloc() to accept task state bitmask
for prepare_to_wait() to support interruptible sleep for callers
that require it.
Previously, this code was assuming uninterruptible sleep for all cases
thus preventing signals from being delivered to a scheduled process
context in the tag stealing slow path.
It now accepts TASK_INTERRUPTIBLE or TASK_UNINTERRUPTIBLE when the
caller is able to sleep waiting for a new tag, or TASK_RUNNING when
the caller cannot sleep, and is forced to return a negative tag.
Reported-by: Linus Torvalds <torva...@linux-foundation.org>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Signed-off-by: Kent Overstreet <k...@daterainc.com>
Cc: <sta...@vger.kernel.org> #3.12+
Signed-off-by: Nicholas Bellinger <n...@linux-iscsi.org>
---
include/linux/percpu_ida.h | 3 ++-
lib/percpu_ida.c | 17 +++++++++++------
2 files changed, 13 insertions(+), 7 deletions(-)
diff --git a/include/linux/percpu_ida.h b/include/linux/percpu_ida.h
index 1900bd0..f5cfdd6 100644
--- a/include/linux/percpu_ida.h
+++ b/include/linux/percpu_ida.h
@@ -4,6 +4,7 @@
#include <linux/types.h>
#include <linux/bitops.h>
#include <linux/init.h>
+#include <linux/sched.h>
#include <linux/spinlock_types.h>
#include <linux/wait.h>
#include <linux/cpumask.h>
@@ -61,7 +62,7 @@ struct percpu_ida {
/* Max size of percpu freelist, */
#define IDA_DEFAULT_PCPU_SIZE ((IDA_DEFAULT_PCPU_BATCH_MOVE * 3) / 2)
-int percpu_ida_alloc(struct percpu_ida *pool, gfp_t gfp);
+int percpu_ida_alloc(struct percpu_ida *pool, int state);
void percpu_ida_free(struct percpu_ida *pool, unsigned tag);
void percpu_ida_destroy(struct percpu_ida *pool);
diff --git a/lib/percpu_ida.c b/lib/percpu_ida.c
index 9d054bf..4579749 100644
--- a/lib/percpu_ida.c
+++ b/lib/percpu_ida.c
@@ -132,22 +132,22 @@ static inline unsigned alloc_local_tag(struct
percpu_ida_cpu *tags)
/**
* percpu_ida_alloc - allocate a tag
* @pool: pool to allocate from
- * @gfp: gfp flags
+ * @state: task state for prepare_to_wait
*
* Returns a tag - an integer in the range [0..nr_tags) (passed to
* tag_pool_init()), or otherwise -ENOSPC on allocation failure.
*
* Safe to be called from interrupt context (assuming it isn't passed
- * __GFP_WAIT, of course).
+ * TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE, of course).
*
* @gfp indicates whether or not to wait until a free id is available (it's not
* used for internal memory allocations); thus if passed __GFP_WAIT we may
sleep
* however long it takes until another thread frees an id (same semantics as a
* mempool).
*
- * Will not fail if passed __GFP_WAIT.
+ * Will not fail if passed TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE.
*/
-int percpu_ida_alloc(struct percpu_ida *pool, gfp_t gfp)
+int percpu_ida_alloc(struct percpu_ida *pool, int state)
{
DEFINE_WAIT(wait);
struct percpu_ida_cpu *tags;
@@ -174,7 +174,7 @@ int percpu_ida_alloc(struct percpu_ida *pool, gfp_t gfp)
*
* global lock held and irqs disabled, don't need percpu lock
*/
- prepare_to_wait(&pool->wait, &wait, TASK_UNINTERRUPTIBLE);
+ prepare_to_wait(&pool->wait, &wait, state);
if (!tags->nr_free)
alloc_global_tags(pool, tags);
@@ -191,9 +191,14 @@ int percpu_ida_alloc(struct percpu_ida *pool, gfp_t gfp)
spin_unlock(&pool->lock);
local_irq_restore(flags);
- if (tag >= 0 || !(gfp & __GFP_WAIT))
+ if (tag >= 0 || state == TASK_RUNNING)
break;
+ if (signal_pending_state(state, current)) {
+ tag = -ERESTARTSYS;
+ break;
+ }
+
schedule();
local_irq_save(flags);
--
1.7.10.4
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
