From: "Li, Ming4" <ming4.li@intel.com>
To: Ira Weiny <ira.weiny@intel.com>, <dave@stgolabs.net>,
<jonathan.cameron@huawei.com>, <dave.jiang@intel.com>,
<alison.schofield@intel.com>, <vishal.l.verma@intel.com>,
<dan.j.williams@intel.com>
Cc: <linux-cxl@vger.kernel.org>
Subject: Re: [PATCH 2/3] cxl/port: Use scoped_guard() to drop device_lock()/unlock pair
Date: Thu, 22 Aug 2024 09:47:57 +0800 [thread overview]
Message-ID: <0072fc05-c9c0-4d82-a92b-4048e4d302c1@intel.com> (raw)
In-Reply-To: <66c66105891fe_1719d2946b@iweiny-mobl.notmuch>
On 8/22/2024 5:49 AM, Ira Weiny wrote:
> Li Ming wrote:
>> A device_lock() and device_unlock() pair can be replaced by a
>> scope-based resource management function scoped_guard() which can make
>> the code more readable and safer. Some device_lock() and device_unlock()
>> pairs in CXL subsystem can be simply replaced by a scoped_guard().
>>
>> Suggested-by: Dan Williams <dan.j.williams@intel.com>
>> Signed-off-by: Li Ming <ming4.li@intel.com>
>> ---
>> drivers/cxl/core/mbox.c | 26 ++++++------
>> drivers/cxl/core/port.c | 87 ++++++++++++++++++---------------------
>> drivers/cxl/core/region.c | 25 ++++++-----
>> drivers/cxl/mem.c | 22 +++++-----
>> drivers/cxl/pmem.c | 16 ++++---
>> 5 files changed, 82 insertions(+), 94 deletions(-)
>>
>> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
>> index e5cdeafdf76e..a8ab5f2697be 100644
>> --- a/drivers/cxl/core/mbox.c
>> +++ b/drivers/cxl/core/mbox.c
>> @@ -1214,19 +1214,19 @@ int cxl_mem_sanitize(struct cxl_memdev *cxlmd, u16 cmd)
>> int rc;
>>
>> /* synchronize with cxl_mem_probe() and decoder write operations */
>> - device_lock(&cxlmd->dev);
>> - endpoint = cxlmd->endpoint;
>> - down_read(&cxl_region_rwsem);
>> - /*
>> - * Require an endpoint to be safe otherwise the driver can not
>> - * be sure that the device is unmapped.
>> - */
>> - if (endpoint && cxl_num_decoders_committed(endpoint) == 0)
>> - rc = __cxl_mem_sanitize(mds, cmd);
>> - else
>> - rc = -EBUSY;
>> - up_read(&cxl_region_rwsem);
>> - device_unlock(&cxlmd->dev);
>> + scoped_guard(device, &cxlmd->dev) {
>> + endpoint = cxlmd->endpoint;
>> + down_read(&cxl_region_rwsem);
>> + /*
>> + * Require an endpoint to be safe otherwise the driver can not
>> + * be sure that the device is unmapped.
>> + */
>> + if (endpoint && cxl_num_decoders_committed(endpoint) == 0)
>> + rc = __cxl_mem_sanitize(mds, cmd);
>> + else
>> + rc = -EBUSY;
>> + up_read(&cxl_region_rwsem);
>> + }
>>
>> return rc;
>> }
>> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
>> index 6119cb3ad25c..53e2593daa95 100644
>> --- a/drivers/cxl/core/port.c
>> +++ b/drivers/cxl/core/port.c
>> @@ -1260,14 +1260,12 @@ static int add_ep(struct cxl_ep *new)
>> struct cxl_port *port = new->dport->port;
>> int rc;
>>
>> - device_lock(&port->dev);
>> - if (port->dead) {
>> - device_unlock(&port->dev);
>> - return -ENXIO;
>> + scoped_guard(device, &port->dev) {
>> + if (port->dead)
>> + return -ENXIO;
>> + rc = xa_insert(&port->endpoints, (unsigned long)new->ep, new,
>> + GFP_KERNEL);
>> }
>> - rc = xa_insert(&port->endpoints, (unsigned long)new->ep, new,
>> - GFP_KERNEL);
>> - device_unlock(&port->dev);
>>
>> return rc;
>> }
>> @@ -1393,14 +1391,14 @@ static void delete_endpoint(void *data)
>> struct cxl_port *endpoint = cxlmd->endpoint;
>> struct device *host = endpoint_host(endpoint);
>>
>> - device_lock(host);
>> - if (host->driver && !endpoint->dead) {
>> - devm_release_action(host, cxl_unlink_parent_dport, endpoint);
>> - devm_release_action(host, cxl_unlink_uport, endpoint);
>> - devm_release_action(host, unregister_port, endpoint);
>> + scoped_guard(device, host) {
>> + if (host->driver && !endpoint->dead) {
>> + devm_release_action(host, cxl_unlink_parent_dport, endpoint);
>> + devm_release_action(host, cxl_unlink_uport, endpoint);
>> + devm_release_action(host, unregister_port, endpoint);
>> + }
>> + cxlmd->endpoint = NULL;
>> }
>> - cxlmd->endpoint = NULL;
>> - device_unlock(host);
>> put_device(&endpoint->dev);
>> put_device(host);
>> }
>> @@ -1562,40 +1560,36 @@ static int add_port_attach_ep(struct cxl_memdev *cxlmd,
>> return -EAGAIN;
>> }
>>
>> - device_lock(&parent_port->dev);
>> - if (!parent_port->dev.driver) {
>> - dev_warn(&cxlmd->dev,
>> - "port %s:%s disabled, failed to enumerate CXL.mem\n",
>> - dev_name(&parent_port->dev), dev_name(uport_dev));
>> - port = ERR_PTR(-ENXIO);
>> - goto out;
>> - }
>> + scoped_guard(device, &parent_port->dev) {
>> + if (!parent_port->dev.driver) {
>> + dev_warn(&cxlmd->dev,
>> + "port %s:%s disabled, failed to enumerate CXL.mem\n",
>> + dev_name(&parent_port->dev), dev_name(uport_dev));
>> + return -ENXIO;
>> + }
>>
>> - port = find_cxl_port_at(parent_port, dport_dev, &dport);
>> - if (!port) {
>> - component_reg_phys = find_component_registers(uport_dev);
>> - port = devm_cxl_add_port(&parent_port->dev, uport_dev,
>> - component_reg_phys, parent_dport);
>> - /* retry find to pick up the new dport information */
>> - if (!IS_ERR(port))
>> + port = find_cxl_port_at(parent_port, dport_dev, &dport);
>> + if (!port) {
>> + component_reg_phys = find_component_registers(uport_dev);
>> + port = devm_cxl_add_port(&parent_port->dev, uport_dev,
>> + component_reg_phys, parent_dport);
>> + if (IS_ERR(port))
>> + return PTR_ERR(port);
>> +
>> + /* retry find to pick up the new dport information */
>> port = find_cxl_port_at(parent_port, dport_dev, &dport);
> Can this call to find_cxl_port_at() fail?
I have thought about it during making this changes.
I was also confused if the find_cxl_port_at() could fail. my understanding is that this new cxl port is just added before calling find_cxl_port_at() with holding the lock of parent_port, the find_cxl_port_at() will always get the cxl_port in this case. other threads have no chance to release the new cxl_port in this case.
>> + }
>> }
>> -out:
>> - device_unlock(&parent_port->dev);
>>
>> - if (IS_ERR(port))
> ^^^^^^^^^^^^
> Does this need to be checked above?
>
> It seems like the logic is changing for the call to cxl_add_ep() but it
> might be ok?
>
> Ira
If my understanding is correct, you meat that above 'IS_ERR(port)' can help to check the result of the above 'port = find_cxl_port_at(parent_port, dport_dev, &dport)', but actually It cannot, because the return of find_cxl_port_at() is a correct cxl port or a NULL. It can help if it is a 'IS_ERR_OR_NULL()'.
>
>> - rc = PTR_ERR(port);
>> - else {
>> - dev_dbg(&cxlmd->dev, "add to new port %s:%s\n",
>> - dev_name(&port->dev), dev_name(port->uport_dev));
>> - rc = cxl_add_ep(dport, &cxlmd->dev);
>> - if (rc == -EBUSY) {
>> - /*
>> - * "can't" happen, but this error code means
>> - * something to the caller, so translate it.
>> - */
>> - rc = -ENXIO;
>> - }
>> + dev_dbg(&cxlmd->dev, "add to new port %s:%s\n",
>> + dev_name(&port->dev), dev_name(port->uport_dev));
>> + rc = cxl_add_ep(dport, &cxlmd->dev);
>> + if (rc == -EBUSY) {
>> + /*
>> + * "can't" happen, but this error code means
>> + * something to the caller, so translate it.
>> + */
>> + rc = -ENXIO;
>> }
>>
>> return rc;
>> @@ -1986,9 +1980,8 @@ int cxl_decoder_add(struct cxl_decoder *cxld, int *target_map)
>>
>> port = to_cxl_port(cxld->dev.parent);
>>
>> - device_lock(&port->dev);
>> - rc = cxl_decoder_add_locked(cxld, target_map);
>> - device_unlock(&port->dev);
>> + scoped_guard(device, &port->dev)
>> + rc = cxl_decoder_add_locked(cxld, target_map);
>>
>> return rc;
>> }
>> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
>> index 21ad5f242875..a3ce7cbe5c6c 100644
>> --- a/drivers/cxl/core/region.c
>> +++ b/drivers/cxl/core/region.c
>> @@ -3094,11 +3094,11 @@ static void cxlr_release_nvdimm(void *_cxlr)
>> struct cxl_region *cxlr = _cxlr;
>> struct cxl_nvdimm_bridge *cxl_nvb = cxlr->cxl_nvb;
>>
>> - device_lock(&cxl_nvb->dev);
>> - if (cxlr->cxlr_pmem)
>> - devm_release_action(&cxl_nvb->dev, cxlr_pmem_unregister,
>> - cxlr->cxlr_pmem);
>> - device_unlock(&cxl_nvb->dev);
>> + scoped_guard(device, &cxl_nvb->dev) {
>> + if (cxlr->cxlr_pmem)
>> + devm_release_action(&cxl_nvb->dev, cxlr_pmem_unregister,
>> + cxlr->cxlr_pmem);
>> + }
>> cxlr->cxl_nvb = NULL;
>> put_device(&cxl_nvb->dev);
>> }
>> @@ -3134,14 +3134,13 @@ static int devm_cxl_add_pmem_region(struct cxl_region *cxlr)
>> dev_dbg(&cxlr->dev, "%s: register %s\n", dev_name(dev->parent),
>> dev_name(dev));
>>
>> - device_lock(&cxl_nvb->dev);
>> - if (cxl_nvb->dev.driver)
>> - rc = devm_add_action_or_reset(&cxl_nvb->dev,
>> - cxlr_pmem_unregister, cxlr_pmem);
>> - else
>> - rc = -ENXIO;
>> - device_unlock(&cxl_nvb->dev);
>> -
>> + scoped_guard(device, &cxl_nvb->dev) {
>> + if (cxl_nvb->dev.driver)
>> + rc = devm_add_action_or_reset(&cxl_nvb->dev,
>> + cxlr_pmem_unregister, cxlr_pmem);
>> + else
>> + rc = -ENXIO;
>> + }
>> if (rc)
>> goto err_bridge;
>>
>> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
>> index ab9b8ab8df44..ae94018a01bd 100644
>> --- a/drivers/cxl/mem.c
>> +++ b/drivers/cxl/mem.c
>> @@ -168,19 +168,17 @@ static int cxl_mem_probe(struct device *dev)
>>
>> cxl_setup_parent_dport(dev, dport);
>>
>> - device_lock(endpoint_parent);
>> - if (!endpoint_parent->driver) {
>> - dev_err(dev, "CXL port topology %s not enabled\n",
>> - dev_name(endpoint_parent));
>> - rc = -ENXIO;
>> - goto unlock;
>> - }
>> + scoped_guard(device, endpoint_parent) {
>> + if (!endpoint_parent->driver) {
>> + dev_err(dev, "CXL port topology %s not enabled\n",
>> + dev_name(endpoint_parent));
>> + return -ENXIO;
>> + }
>>
>> - rc = devm_cxl_add_endpoint(endpoint_parent, cxlmd, dport);
>> -unlock:
>> - device_unlock(endpoint_parent);
>> - if (rc)
>> - return rc;
>> + rc = devm_cxl_add_endpoint(endpoint_parent, cxlmd, dport);
>> + if (rc)
>> + return rc;
>> + }
>>
>> /*
>> * The kernel may be operating out of CXL memory on this device,
>> diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
>> index 4ef93da22335..647c7e25ef3a 100644
>> --- a/drivers/cxl/pmem.c
>> +++ b/drivers/cxl/pmem.c
>> @@ -233,15 +233,13 @@ static int detach_nvdimm(struct device *dev, void *data)
>> if (!is_cxl_nvdimm(dev))
>> return 0;
>>
>> - device_lock(dev);
>> - if (!dev->driver)
>> - goto out;
>> -
>> - cxl_nvd = to_cxl_nvdimm(dev);
>> - if (cxl_nvd->cxlmd && cxl_nvd->cxlmd->cxl_nvb == data)
>> - release = true;
>> -out:
>> - device_unlock(dev);
>> + scoped_guard(device, dev) {
>> + if (dev->driver) {
>> + cxl_nvd = to_cxl_nvdimm(dev);
>> + if (cxl_nvd->cxlmd && cxl_nvd->cxlmd->cxl_nvb == data)
>> + release = true;
>> + }
>> + }
>> if (release)
>> device_release_driver(dev);
>> return 0;
>> --
>> 2.40.1
>>
>
next prev parent reply other threads:[~2024-08-22 1:48 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-13 7:05 [PATCH 1/3] cxl/port: Use __free() to drop put_device() for cxl_port Li Ming
2024-08-13 7:05 ` [PATCH 2/3] cxl/port: Use scoped_guard() to drop device_lock()/unlock pair Li Ming
2024-08-21 21:49 ` Ira Weiny
2024-08-22 1:47 ` Li, Ming4 [this message]
2024-08-13 7:05 ` [PATCH 3/3] cxl/port: Refactor __devm_cxl_add_port() to drop goto pattern Li Ming
2024-08-21 22:01 ` Ira Weiny
2024-08-22 2:07 ` Li, Ming4
2024-08-21 21:37 ` [PATCH 1/3] cxl/port: Use __free() to drop put_device() for cxl_port Ira Weiny
2024-08-22 1:26 ` Li, Ming4
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