126 lines
4.3 KiB
Diff
126 lines
4.3 KiB
Diff
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
|
|
Date: Wed, 18 Feb 2015 18:37:26 +0100
|
|
Subject: block/mq: drop per ctx cpu_lock
|
|
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.4/patches-4.4-rt2.tar.xz
|
|
|
|
While converting the get_cpu() to get_cpu_light() I added a cpu lock to
|
|
ensure the same code is not invoked twice on the same CPU. And now I run
|
|
into this:
|
|
|
|
| kernel BUG at kernel/locking/rtmutex.c:996!
|
|
| invalid opcode: 0000 [#1] PREEMPT SMP
|
|
| CPU0: 13 PID: 75 Comm: kworker/u258:0 Tainted: G I 3.18.7-rt1.5+ #12
|
|
| Workqueue: writeback bdi_writeback_workfn (flush-8:0)
|
|
| task: ffff88023742a620 ti: ffff88023743c000 task.ti: ffff88023743c000
|
|
| RIP: 0010:[<ffffffff81523cc0>] [<ffffffff81523cc0>] rt_spin_lock_slowlock+0x280/0x2d0
|
|
| Call Trace:
|
|
| [<ffffffff815254e7>] rt_spin_lock+0x27/0x60
|
|
taking the same lock again
|
|
|
|
|
| [<ffffffff8127c771>] blk_mq_insert_requests+0x51/0x130
|
|
| [<ffffffff8127d4a9>] blk_mq_flush_plug_list+0x129/0x140
|
|
| [<ffffffff81272461>] blk_flush_plug_list+0xd1/0x250
|
|
| [<ffffffff81522075>] schedule+0x75/0xa0
|
|
| [<ffffffff8152474d>] do_nanosleep+0xdd/0x180
|
|
| [<ffffffff810c8312>] __hrtimer_nanosleep+0xd2/0x1c0
|
|
| [<ffffffff810c8456>] cpu_chill+0x56/0x80
|
|
| [<ffffffff8107c13d>] try_to_grab_pending+0x1bd/0x390
|
|
| [<ffffffff8107c431>] cancel_delayed_work+0x21/0x170
|
|
| [<ffffffff81279a98>] blk_mq_stop_hw_queue+0x18/0x40
|
|
| [<ffffffffa000ac6f>] scsi_queue_rq+0x7f/0x830 [scsi_mod]
|
|
| [<ffffffff8127b0de>] __blk_mq_run_hw_queue+0x1ee/0x360
|
|
| [<ffffffff8127b528>] blk_mq_map_request+0x108/0x190
|
|
take the lock ^^^
|
|
|
|
|
| [<ffffffff8127c8d2>] blk_sq_make_request+0x82/0x350
|
|
| [<ffffffff8126f6c0>] generic_make_request+0xd0/0x120
|
|
| [<ffffffff8126f788>] submit_bio+0x78/0x190
|
|
| [<ffffffff811bd537>] _submit_bh+0x117/0x180
|
|
| [<ffffffff811bf528>] __block_write_full_page.constprop.38+0x138/0x3f0
|
|
| [<ffffffff811bf880>] block_write_full_page+0xa0/0xe0
|
|
| [<ffffffff811c02b3>] blkdev_writepage+0x13/0x20
|
|
| [<ffffffff81127b25>] __writepage+0x15/0x40
|
|
| [<ffffffff8112873b>] write_cache_pages+0x1fb/0x440
|
|
| [<ffffffff811289be>] generic_writepages+0x3e/0x60
|
|
| [<ffffffff8112a17c>] do_writepages+0x1c/0x30
|
|
| [<ffffffff811b3603>] __writeback_single_inode+0x33/0x140
|
|
| [<ffffffff811b462d>] writeback_sb_inodes+0x2bd/0x490
|
|
| [<ffffffff811b4897>] __writeback_inodes_wb+0x97/0xd0
|
|
| [<ffffffff811b4a9b>] wb_writeback+0x1cb/0x210
|
|
| [<ffffffff811b505b>] bdi_writeback_workfn+0x25b/0x380
|
|
| [<ffffffff8107b50b>] process_one_work+0x1bb/0x490
|
|
| [<ffffffff8107c7ab>] worker_thread+0x6b/0x4f0
|
|
| [<ffffffff81081863>] kthread+0xe3/0x100
|
|
| [<ffffffff8152627c>] ret_from_fork+0x7c/0xb0
|
|
|
|
After looking at this for a while it seems that it is save if blk_mq_ctx is
|
|
used multiple times, the in struct lock protects the access.
|
|
|
|
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
|
|
---
|
|
block/blk-mq.c | 4 ----
|
|
block/blk-mq.h | 8 --------
|
|
2 files changed, 12 deletions(-)
|
|
|
|
--- a/block/blk-mq.c
|
|
+++ b/block/blk-mq.c
|
|
@@ -1405,9 +1405,7 @@ static blk_qc_t blk_sq_make_request(stru
|
|
blk_mq_put_ctx(data.ctx);
|
|
|
|
if (request_count >= BLK_MAX_REQUEST_COUNT) {
|
|
- spin_unlock(&data.ctx->cpu_lock);
|
|
blk_flush_plug_list(plug, false);
|
|
- spin_lock(&data.ctx->cpu_lock);
|
|
trace_block_plug(q);
|
|
}
|
|
|
|
@@ -1609,7 +1607,6 @@ static int blk_mq_hctx_cpu_offline(struc
|
|
blk_mq_hctx_clear_pending(hctx, ctx);
|
|
}
|
|
spin_unlock(&ctx->lock);
|
|
- __blk_mq_put_ctx(ctx);
|
|
|
|
if (list_empty(&tmp))
|
|
return NOTIFY_OK;
|
|
@@ -1803,7 +1800,6 @@ static void blk_mq_init_cpu_queues(struc
|
|
memset(__ctx, 0, sizeof(*__ctx));
|
|
__ctx->cpu = i;
|
|
spin_lock_init(&__ctx->lock);
|
|
- spin_lock_init(&__ctx->cpu_lock);
|
|
INIT_LIST_HEAD(&__ctx->rq_list);
|
|
__ctx->queue = q;
|
|
|
|
--- a/block/blk-mq.h
|
|
+++ b/block/blk-mq.h
|
|
@@ -9,7 +9,6 @@ struct blk_mq_ctx {
|
|
struct list_head rq_list;
|
|
} ____cacheline_aligned_in_smp;
|
|
|
|
- spinlock_t cpu_lock;
|
|
unsigned int cpu;
|
|
unsigned int index_hw;
|
|
|
|
@@ -78,7 +77,6 @@ static inline struct blk_mq_ctx *__blk_m
|
|
struct blk_mq_ctx *ctx;
|
|
|
|
ctx = per_cpu_ptr(q->queue_ctx, cpu);
|
|
- spin_lock(&ctx->cpu_lock);
|
|
return ctx;
|
|
}
|
|
|
|
@@ -93,14 +91,8 @@ static inline struct blk_mq_ctx *blk_mq_
|
|
return __blk_mq_get_ctx(q, get_cpu_light());
|
|
}
|
|
|
|
-static void __blk_mq_put_ctx(struct blk_mq_ctx *ctx)
|
|
-{
|
|
- spin_unlock(&ctx->cpu_lock);
|
|
-}
|
|
-
|
|
static inline void blk_mq_put_ctx(struct blk_mq_ctx *ctx)
|
|
{
|
|
- __blk_mq_put_ctx(ctx);
|
|
put_cpu_light();
|
|
}
|
|
|