From: Jason Gunthorpe <jgg@nvidia.com>
To: Nicolin Chen <nicolinc@nvidia.com>
Cc: Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Joerg Roedel <joro@8bytes.org>,
Bjorn Helgaas <bhelgaas@google.com>,
"Rafael J . Wysocki" <rafael@kernel.org>,
Len Brown <lenb@kernel.org>,
Pranjal Shrivastava <praan@google.com>,
Mostafa Saleh <smostafa@google.com>,
Lu Baolu <baolu.lu@linux.intel.com>,
Kevin Tian <kevin.tian@intel.com>,
linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
linux-pci@vger.kernel.org, vsethi@nvidia.com,
Shuai Xue <xueshuai@linux.alibaba.com>
Subject: Re: [PATCH v4 07/24] iommu: Defer __iommu_group_free_device() to be outside group->mutex
Date: Tue, 19 May 2026 08:47:09 -0300 [thread overview]
Message-ID: <20260519114709.GP787748@nvidia.com> (raw)
In-Reply-To: <bae489d600425a014bfed1c2290ee7c0c657f198.1779161849.git.nicolinc@nvidia.com>
On Mon, May 18, 2026 at 08:38:50PM -0700, Nicolin Chen wrote:
> __iommu_group_remove_device() holds group->mutex across the entire call to
> __iommu_group_free_device() that performs sysfs removals, tracing, and the
> final kfree(). But in fact, most of these operations don't really need the
> group->mutex.
Are you sure? sysfs requires unique names, and this mutex is providing
a guarentee that will happen. While it shouldn't be possible to race
remove and attach, it is easier to reason about if we don't have to
make this assumption.
> Subsequent changes will introduce sleepable operations to this function:
> + synchronize_rcu() to defer the gdev->dev put past a grace period.
I'm not keen on that at all.
Jason
next prev parent reply other threads:[~2026-05-19 11:47 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-19 3:38 [PATCH v4 00/24] iommu/arm-smmu-v3: Quarantine device upon ATC invalidation timeout Nicolin Chen
2026-05-19 3:38 ` [PATCH v4 01/24] PCI: Don't suspend IOMMU when probing reset capability Nicolin Chen
2026-05-19 3:38 ` [PATCH v4 02/24] PCI: Propagate FLR return values to callers Nicolin Chen
2026-05-19 3:38 ` [PATCH v4 03/24] iommu: Convert gdev->blocked from bool to enum gdev_blocked Nicolin Chen
2026-05-19 3:38 ` [PATCH v4 04/24] iommu: Pass in reset result to pci_dev_reset_iommu_done() Nicolin Chen
2026-05-19 3:38 ` [PATCH v4 05/24] iommu: Add reset_device_done callback for hardware fault recovery Nicolin Chen
2026-05-19 3:38 ` [PATCH v4 06/24] iommu: Defer iommu_group free via kfree_rcu() Nicolin Chen
2026-05-19 11:39 ` Jason Gunthorpe
2026-05-19 18:54 ` Nicolin Chen
2026-05-19 3:38 ` [PATCH v4 07/24] iommu: Defer __iommu_group_free_device() to be outside group->mutex Nicolin Chen
2026-05-19 11:47 ` Jason Gunthorpe [this message]
2026-05-19 3:38 ` [PATCH v4 08/24] iommu: Change group->devices to RCU-protected list Nicolin Chen
2026-05-19 3:38 ` [PATCH v4 09/24] iommu: Add group pointer to struct group_device Nicolin Chen
2026-05-19 3:38 ` [PATCH v4 10/24] iommu: Add __iommu_group_block_device helper Nicolin Chen
2026-05-19 3:38 ` [PATCH v4 11/24] iommu: Add iommu_report_device_broken() to quarantine a broken device Nicolin Chen
2026-05-19 12:07 ` Jason Gunthorpe
2026-05-19 18:29 ` Nicolin Chen
2026-05-19 19:16 ` Jason Gunthorpe
2026-05-19 3:38 ` [PATCH v4 12/24] iommu/arm-smmu-v3: Mark ATC invalidate timeouts via lockless bitmap Nicolin Chen
2026-05-19 3:38 ` [PATCH v4 13/24] iommu/arm-smmu-v3: Skip remaining GERROR causes on SFM Nicolin Chen
2026-05-19 3:38 ` [PATCH v4 14/24] iommu/arm-smmu-v3: Introduce per-cmdq cmdq_err_handler callback Nicolin Chen
2026-05-19 3:38 ` [PATCH v4 15/24] iommu/arm-smmu-v3: Co-clear pending CMDQ_ERR when CMD_SYNC times out Nicolin Chen
2026-05-19 3:38 ` [PATCH v4 16/24] iommu/arm-smmu-v3: Co-clear pending CMDQ_ERR when queue_has_space() fails Nicolin Chen
2026-05-19 3:39 ` [PATCH v4 17/24] iommu/arm-smmu-v3: Add master in arm_smmu_inv for ATS entries Nicolin Chen
2026-05-19 12:01 ` Jason Gunthorpe
2026-05-19 3:39 ` [PATCH v4 18/24] iommu/arm-smmu-v3: Introduce master->ats_broken flag Nicolin Chen
2026-05-19 12:06 ` Jason Gunthorpe
2026-05-19 3:39 ` [PATCH v4 19/24] iommu/arm-smmu-v3: Add invs and has_ats to struct arm_smmu_cmdq_batch Nicolin Chen
2026-05-19 12:09 ` Jason Gunthorpe
2026-05-19 3:39 ` [PATCH v4 20/24] iommu/arm-smmu-v3: Introduce arm_smmu_cmdq_batch_issue() wrapper Nicolin Chen
2026-05-19 3:39 ` [PATCH v4 21/24] iommu/arm-smmu-v3: Move arm_smmu_invs_for_each_entry to header Nicolin Chen
2026-05-19 3:39 ` [PATCH v4 22/24] iommu/arm-smmu-v3: Introduce master->ats_invs Nicolin Chen
2026-05-19 12:12 ` Jason Gunthorpe
2026-05-19 3:39 ` [PATCH v4 23/24] iommu/arm-smmu-v3: Serialize STE.EATS and ats_broken updates Nicolin Chen
2026-05-19 3:39 ` [PATCH v4 24/24] iommu/arm-smmu-v3: Block ATS upon an ATC invalidation timeout Nicolin Chen
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