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76 lines
2.6 KiB
76 lines
2.6 KiB
9 months ago
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From ac9dc8ea241ef6d3a0447d696620d4d4053b71bf Mon Sep 17 00:00:00 2001
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From: Stefan Hajnoczi <stefanha@redhat.com>
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Date: Mon, 4 Dec 2023 11:42:59 -0500
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Subject: [PATCH 080/101] dma-helpers: don't lock AioContext in dma_blk_cb()
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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RH-MergeRequest: 214: Remove AioContext lock
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RH-Jira: RHEL-15965
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Commit: [11/26] a8580463ba6aee4ca248c0b947b9e72bd9e87aab (kmwolf/centos-qemu-kvm)
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Commit abfcd2760b3e ("dma-helpers: prevent dma_blk_cb() vs
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dma_aio_cancel() race") acquired the AioContext lock inside dma_blk_cb()
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to avoid a race with scsi_device_purge_requests() running in the main
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loop thread.
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The SCSI code no longer calls dma_aio_cancel() from the main loop thread
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while I/O is running in the IOThread AioContext. Therefore it is no
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longer necessary to take this lock to protect DMAAIOCB fields. The
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->cb() function also does not require the lock because blk_aio_*() and
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friends do not need the AioContext lock.
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Both hw/ide/core.c and hw/ide/macio.c also call dma_blk_io() but don't
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rely on it taking the AioContext lock, so this change is safe.
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Reviewed-by: Kevin Wolf <kwolf@redhat.com>
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Message-ID: <20231204164259.1515217-5-stefanha@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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---
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system/dma-helpers.c | 7 ++-----
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1 file changed, 2 insertions(+), 5 deletions(-)
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diff --git a/system/dma-helpers.c b/system/dma-helpers.c
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index 36211acc7e..528117f256 100644
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--- a/system/dma-helpers.c
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+++ b/system/dma-helpers.c
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@@ -119,13 +119,12 @@ static void dma_blk_cb(void *opaque, int ret)
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trace_dma_blk_cb(dbs, ret);
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- aio_context_acquire(ctx);
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dbs->acb = NULL;
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dbs->offset += dbs->iov.size;
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if (dbs->sg_cur_index == dbs->sg->nsg || ret < 0) {
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dma_complete(dbs, ret);
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- goto out;
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+ return;
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}
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dma_blk_unmap(dbs);
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@@ -168,7 +167,7 @@ static void dma_blk_cb(void *opaque, int ret)
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trace_dma_map_wait(dbs);
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dbs->bh = aio_bh_new(ctx, reschedule_dma, dbs);
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cpu_register_map_client(dbs->bh);
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- goto out;
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+ return;
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}
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if (!QEMU_IS_ALIGNED(dbs->iov.size, dbs->align)) {
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@@ -179,8 +178,6 @@ static void dma_blk_cb(void *opaque, int ret)
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dbs->acb = dbs->io_func(dbs->offset, &dbs->iov,
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dma_blk_cb, dbs, dbs->io_func_opaque);
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assert(dbs->acb);
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-out:
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- aio_context_release(ctx);
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}
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static void dma_aio_cancel(BlockAIOCB *acb)
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--
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2.39.3
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