92 lines
2.7 KiB
Diff
92 lines
2.7 KiB
Diff
From 7632d1dd96f75bdba997003fa61ab14e57afb0fe Mon Sep 17 00:00:00 2001
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Wed, 9 Apr 2014 10:37:23 +0200
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Subject: [PATCH 5/5] block: mq: use cpu_light()
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.0/patches-4.0.5-rt3.tar.xz
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there is a might sleep splat because get_cpu() disables preemption and
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later we grab a lock. As a workaround for this we use get_cpu_light()
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and an additional lock to prevent taking the same ctx.
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There is a lock member in the ctx already but there some functions which do ++
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on the member and this works with irq off but on RT we would need the extra lock.
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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block/blk-mq.c | 4 ++++
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block/blk-mq.h | 17 ++++++++++++++---
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2 files changed, 18 insertions(+), 3 deletions(-)
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--- a/block/blk-mq.c
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+++ b/block/blk-mq.c
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@@ -1353,7 +1353,9 @@ static void blk_sq_make_request(struct r
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if (list_empty(&plug->mq_list))
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trace_block_plug(q);
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else if (request_count >= BLK_MAX_REQUEST_COUNT) {
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+ spin_unlock(&data.ctx->cpu_lock);
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blk_flush_plug_list(plug, false);
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+ spin_lock(&data.ctx->cpu_lock);
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trace_block_plug(q);
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}
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list_add_tail(&rq->queuelist, &plug->mq_list);
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@@ -1548,6 +1550,7 @@ static int blk_mq_hctx_cpu_offline(struc
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blk_mq_hctx_clear_pending(hctx, ctx);
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}
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spin_unlock(&ctx->lock);
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+ __blk_mq_put_ctx(ctx);
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if (list_empty(&tmp))
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return NOTIFY_OK;
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@@ -1741,6 +1744,7 @@ static void blk_mq_init_cpu_queues(struc
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memset(__ctx, 0, sizeof(*__ctx));
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__ctx->cpu = i;
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spin_lock_init(&__ctx->lock);
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+ spin_lock_init(&__ctx->cpu_lock);
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INIT_LIST_HEAD(&__ctx->rq_list);
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__ctx->queue = q;
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--- a/block/blk-mq.h
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+++ b/block/blk-mq.h
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@@ -9,6 +9,7 @@ struct blk_mq_ctx {
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struct list_head rq_list;
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} ____cacheline_aligned_in_smp;
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+ spinlock_t cpu_lock;
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unsigned int cpu;
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unsigned int index_hw;
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@@ -76,7 +77,11 @@ struct blk_align_bitmap {
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static inline struct blk_mq_ctx *__blk_mq_get_ctx(struct request_queue *q,
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unsigned int cpu)
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{
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- return per_cpu_ptr(q->queue_ctx, cpu);
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+ struct blk_mq_ctx *ctx;
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+
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+ ctx = per_cpu_ptr(q->queue_ctx, cpu);
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+ spin_lock(&ctx->cpu_lock);
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+ return ctx;
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}
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/*
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@@ -87,12 +92,18 @@ static inline struct blk_mq_ctx *__blk_m
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*/
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static inline struct blk_mq_ctx *blk_mq_get_ctx(struct request_queue *q)
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{
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- return __blk_mq_get_ctx(q, get_cpu());
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+ return __blk_mq_get_ctx(q, get_cpu_light());
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+}
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+
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+static void __blk_mq_put_ctx(struct blk_mq_ctx *ctx)
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+{
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+ spin_unlock(&ctx->cpu_lock);
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}
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static inline void blk_mq_put_ctx(struct blk_mq_ctx *ctx)
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{
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- put_cpu();
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+ __blk_mq_put_ctx(ctx);
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+ put_cpu_light();
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}
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struct blk_mq_alloc_data {
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