[PATCH] percpu_ida: Handle out-of-tags gracefully
From: Bart Van Assche
Date: Mon Mar 10 2014 - 10:12:48 EST
Avoid that percpu_ida_alloc() hangs or crashes if there are still
tags are available. Wait until a tag becomes available instead of
giving up when running out of tags temporarily. This patch fixes
the following kernel bug:
------------[ cut here ]------------
kernel BUG at lib/percpu_ida.c:81!
invalid opcode: 0000 [#1] SMP
RIP: 0010:[<ffffffff8120f00e>] [<ffffffff8120f00e>] percpu_ida_alloc+0x33e/0x370
Call Trace:
[<ffffffff811ef95f>] blk_mq_get_tag+0x2f/0x50
[<ffffffff811ed79c>] blk_mq_alloc_rq.isra.17+0x1c/0x90
[<ffffffff811eeb9b>] blk_mq_alloc_request_pinned+0x9b/0x110
[<ffffffff811ef4c6>] blk_mq_make_request+0x426/0x480
[<ffffffff811e28f0>] generic_make_request+0xc0/0x110
[<ffffffff811e29ab>] submit_bio+0x6b/0x140
[<ffffffff8117aabb>] _submit_bh+0x13b/0x220
[<ffffffff8117d70f>] block_read_full_page+0x1ff/0x300
[<ffffffff81181128>] blkdev_readpage+0x18/0x20
[<ffffffff811067b7>] __do_page_cache_readahead+0x277/0x280
[<ffffffff81106d1d>] force_page_cache_readahead+0x8d/0xc0
[<ffffffff81106d9b>] page_cache_sync_readahead+0x4b/0x50
[<ffffffff810fdf05>] generic_file_aio_read+0x4c5/0x700
[<ffffffff8118147b>] blkdev_aio_read+0x4b/0x70
[<ffffffff8114a28a>] do_sync_read+0x5a/0x90
[<ffffffff8114a8cb>] vfs_read+0x9b/0x160
[<ffffffff8114b389>] SyS_read+0x49/0xa0
[<ffffffff81416049>] tracesys+0xd0/0xd5
---[ end trace cdd1a8a7968266cf ]---
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
Cc: Kent Overstreet <kmo@xxxxxxxxxxxxx>
Cc: Shaohua Li <shli@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Alexander Gordeev <agordeev@xxxxxxxxxx>
Cc: Mike Christie <michaelc@xxxxxxxxxxx>
---
lib/percpu_ida.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/lib/percpu_ida.c b/lib/percpu_ida.c
index 93d145e..170d27c 100644
--- a/lib/percpu_ida.c
+++ b/lib/percpu_ida.c
@@ -73,7 +73,7 @@ static inline void steal_tags(struct percpu_ida *pool,
if (cpu >= nr_cpu_ids) {
cpu = cpumask_first(&pool->cpus_have_tags);
if (cpu >= nr_cpu_ids)
- BUG();
+ break;
}
pool->cpu_last_stolen = cpu;
@@ -189,6 +189,9 @@ int percpu_ida_alloc(struct percpu_ida *pool, int state)
spin_unlock(&pool->lock);
local_irq_restore(flags);
+ if (tags->nr_free)
+ wake_up(&pool->wait);
+
if (tag >= 0 || state == TASK_RUNNING)
break;
--
1.8.4.5
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