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Date: Mon, 10 Mar 2014 15:12:33 +0100 From: Bart Van Assche <bvanassche@....org> To: Jens Axboe <axboe@...nel.dk> CC: Kent Overstreet <kmo@...erainc.com>, Shaohua Li <shli@...nel.org>, Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>, Alexander Gordeev <agordeev@...hat.com>, Mike Christie <michaelc@...wisc.edu>, linux-kernel <linux-kernel@...r.kernel.org> Subject: [PATCH] percpu_ida: Handle out-of-tags gracefully 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@....org> Cc: Kent Overstreet <kmo@...erainc.com> Cc: Shaohua Li <shli@...nel.org> Cc: Christoph Hellwig <hch@....de> Cc: Jens Axboe <axboe@...nel.dk> Cc: Alexander Gordeev <agordeev@...hat.com> Cc: Mike Christie <michaelc@...wisc.edu> --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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