From: Nicolin Chen <nicoleotsuka@gmail.com>
To: thierry.reding@gmail.com, joro@8bytes.org
Cc: vdumpa@nvidia.com, jonathanh@nvidia.com, digetx@gmail.com,
linux-tegra@vger.kernel.org, iommu@lists.linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: [PATCH v2 2/2] iommu/tegra-smmu: Expend mutex protection range
Date: Mon, 28 Sep 2020 16:59:01 -0700 [thread overview]
Message-ID: <20200928235901.28337-3-nicoleotsuka@gmail.com> (raw)
In-Reply-To: <20200928235901.28337-1-nicoleotsuka@gmail.com>
This is used to protect potential race condition at use_count.
since probes of client drivers, calling attach_dev(), may run
concurrently.
Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
---
Changelog
v1->v2:
* N/A
drivers/iommu/tegra-smmu.c | 34 +++++++++++++++++++++-------------
1 file changed, 21 insertions(+), 13 deletions(-)
diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c
index ec4c9dafff95..acda5902e095 100644
--- a/drivers/iommu/tegra-smmu.c
+++ b/drivers/iommu/tegra-smmu.c
@@ -256,26 +256,19 @@ static int tegra_smmu_alloc_asid(struct tegra_smmu *smmu, unsigned int *idp)
{
unsigned long id;
- mutex_lock(&smmu->lock);
-
id = find_first_zero_bit(smmu->asids, smmu->soc->num_asids);
- if (id >= smmu->soc->num_asids) {
- mutex_unlock(&smmu->lock);
+ if (id >= smmu->soc->num_asids)
return -ENOSPC;
- }
set_bit(id, smmu->asids);
*idp = id;
- mutex_unlock(&smmu->lock);
return 0;
}
static void tegra_smmu_free_asid(struct tegra_smmu *smmu, unsigned int id)
{
- mutex_lock(&smmu->lock);
clear_bit(id, smmu->asids);
- mutex_unlock(&smmu->lock);
}
static bool tegra_smmu_capable(enum iommu_cap cap)
@@ -420,17 +413,21 @@ static int tegra_smmu_as_prepare(struct tegra_smmu *smmu,
struct tegra_smmu_as *as)
{
u32 value;
- int err;
+ int err = 0;
+
+ mutex_lock(&smmu->lock);
if (as->use_count > 0) {
as->use_count++;
- return 0;
+ goto err_unlock;
}
as->pd_dma = dma_map_page(smmu->dev, as->pd, 0, SMMU_SIZE_PD,
DMA_TO_DEVICE);
- if (dma_mapping_error(smmu->dev, as->pd_dma))
- return -ENOMEM;
+ if (dma_mapping_error(smmu->dev, as->pd_dma)) {
+ err = -ENOMEM;
+ goto err_unlock;
+ }
/* We can't handle 64-bit DMA addresses */
if (!smmu_dma_addr_valid(smmu, as->pd_dma)) {
@@ -453,24 +450,35 @@ static int tegra_smmu_as_prepare(struct tegra_smmu *smmu,
as->smmu = smmu;
as->use_count++;
+ mutex_unlock(&smmu->lock);
+
return 0;
err_unmap:
dma_unmap_page(smmu->dev, as->pd_dma, SMMU_SIZE_PD, DMA_TO_DEVICE);
+err_unlock:
+ mutex_unlock(&smmu->lock);
+
return err;
}
static void tegra_smmu_as_unprepare(struct tegra_smmu *smmu,
struct tegra_smmu_as *as)
{
- if (--as->use_count > 0)
+ mutex_lock(&smmu->lock);
+
+ if (--as->use_count > 0) {
+ mutex_unlock(&smmu->lock);
return;
+ }
tegra_smmu_free_asid(smmu, as->id);
dma_unmap_page(smmu->dev, as->pd_dma, SMMU_SIZE_PD, DMA_TO_DEVICE);
as->smmu = NULL;
+
+ mutex_unlock(&smmu->lock);
}
static int tegra_smmu_attach_dev(struct iommu_domain *domain,
--
2.17.1
next prev parent reply other threads:[~2020-09-29 0:04 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-28 23:58 [PATCH v2 0/2] iommu/tegra-smmu: Two followup changes Nicolin Chen
2020-09-28 23:59 ` [PATCH v2 1/2] iommu/tegra-smmu: Unwrap tegra_smmu_group_get Nicolin Chen
2020-09-28 23:59 ` Nicolin Chen [this message]
2020-09-29 0:17 ` [PATCH v2 2/2] iommu/tegra-smmu: Expend mutex protection range Dmitry Osipenko
2020-09-29 1:15 ` Nicolin Chen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200928235901.28337-3-nicoleotsuka@gmail.com \
--to=nicoleotsuka@gmail.com \
--cc=digetx@gmail.com \
--cc=iommu@lists.linux-foundation.org \
--cc=jonathanh@nvidia.com \
--cc=joro@8bytes.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tegra@vger.kernel.org \
--cc=thierry.reding@gmail.com \
--cc=vdumpa@nvidia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).