linux/debian/patches/features/all/rt/block-mq-use-cpu_light.patch

92 lines
2.7 KiB
Diff

From 7632d1dd96f75bdba997003fa61ab14e57afb0fe Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 9 Apr 2014 10:37:23 +0200
Subject: [PATCH 5/5] block: mq: use cpu_light()
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/3.14/patches-3.14.10-rt7.tar.xz
there is a might sleep splat because get_cpu() disables preemption and
later we grab a lock. As a workaround for this we use get_cpu_light()
and an additional lock to prevent taking the same ctx.
There is a lock member in the ctx already but there some functions which do ++
on the member and this works with irq off but on RT we would need the extra lock.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
block/blk-mq.c | 20 +++++++++++++++++---
block/blk-mq.h | 1 +
2 files changed, 18 insertions(+), 3 deletions(-)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -30,7 +30,11 @@ static void __blk_mq_run_hw_queue(struct
static struct blk_mq_ctx *__blk_mq_get_ctx(struct request_queue *q,
unsigned int cpu)
{
- return per_cpu_ptr(q->queue_ctx, cpu);
+ struct blk_mq_ctx *ctx;
+
+ ctx = per_cpu_ptr(q->queue_ctx, cpu);
+ spin_lock(&ctx->cpu_lock);
+ return ctx;
}
/*
@@ -41,12 +45,18 @@ static struct blk_mq_ctx *__blk_mq_get_c
*/
static struct blk_mq_ctx *blk_mq_get_ctx(struct request_queue *q)
{
- return __blk_mq_get_ctx(q, get_cpu());
+ 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 void blk_mq_put_ctx(struct blk_mq_ctx *ctx)
{
- put_cpu();
+ __blk_mq_put_ctx(ctx);
+ put_cpu_light();
}
/*
@@ -897,7 +907,9 @@ static void blk_mq_make_request(struct r
if (list_empty(&plug->mq_list))
trace_block_plug(q);
else if (request_count >= BLK_MAX_REQUEST_COUNT) {
+ spin_unlock(&ctx->cpu_lock);
blk_flush_plug_list(plug, false);
+ spin_lock(&ctx->cpu_lock);
trace_block_plug(q);
}
list_add_tail(&rq->queuelist, &plug->mq_list);
@@ -973,6 +985,7 @@ static void blk_mq_hctx_notify(void *dat
clear_bit(ctx->index_hw, hctx->ctx_map);
}
spin_unlock(&ctx->lock);
+ __blk_mq_put_ctx(ctx);
if (list_empty(&tmp))
return;
@@ -1212,6 +1225,7 @@ 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
@@ -7,6 +7,7 @@ struct blk_mq_ctx {
struct list_head rq_list;
} ____cacheline_aligned_in_smp;
+ spinlock_t cpu_lock;
unsigned int cpu;
unsigned int index_hw;
unsigned int ipi_redirect;