diff mbox series

cxl/hdm: Fix dpa translation locking

Message ID 170192142664.461900.3169528633970716889.stgit@dwillia2-xfh.jf.intel.com
State New, archived
Headers show
Series cxl/hdm: Fix dpa translation locking | expand

Commit Message

Dan Williams Dec. 7, 2023, 3:57 a.m. UTC
The helper, cxl_dpa_resource_start(), snapshots the dpa-address of an
endpoint-decoder after acquiring the cxl_dpa_rwsem. However, it is
sufficient to assert that cxl_dpa_rwsem is held rather than acquire it
in the helper. Otherwise, it triggers multiple lockdep reports:

1/ Tracing callbacks are in an atomic context that can not acquire sleeping
locks:

    BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1525
    in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1288, name: bash
    preempt_count: 2, expected: 0
    RCU nest depth: 0, expected: 0
    [..]
    Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20230524-3.fc38 05/24/2023
    Call Trace:
     <TASK>
     dump_stack_lvl+0x71/0x90
     __might_resched+0x1b2/0x2c0
     down_read+0x1a/0x190
     cxl_dpa_resource_start+0x15/0x50 [cxl_core]
     cxl_trace_hpa+0x122/0x300 [cxl_core]
     trace_event_raw_event_cxl_poison+0x1c9/0x2d0 [cxl_core]

2/ The rwsem is already held in the inject poison path:

    WARNING: possible recursive locking detected
    6.7.0-rc2+ #12 Tainted: G        W  OE    N
    --------------------------------------------
    bash/1288 is trying to acquire lock:
    ffffffffc05f73d0 (cxl_dpa_rwsem){++++}-{3:3}, at: cxl_dpa_resource_start+0x15/0x50 [cxl_core]

    but task is already holding lock:
    ffffffffc05f73d0 (cxl_dpa_rwsem){++++}-{3:3}, at: cxl_inject_poison+0x7d/0x1e0 [cxl_core]
    [..]
    Call Trace:
     <TASK>
     dump_stack_lvl+0x71/0x90
     __might_resched+0x1b2/0x2c0
     down_read+0x1a/0x190
     cxl_dpa_resource_start+0x15/0x50 [cxl_core]
     cxl_trace_hpa+0x122/0x300 [cxl_core]
     trace_event_raw_event_cxl_poison+0x1c9/0x2d0 [cxl_core]
     __traceiter_cxl_poison+0x5c/0x80 [cxl_core]
     cxl_inject_poison+0x1bc/0x1e0 [cxl_core]

This appears to have been an issue since the initial implementation and
uncovered by the new cxl-poison.sh test [1]. That test is now passing with
these changes.

Fixes: 28a3ae4ff66c ("cxl/trace: Add an HPA to cxl_poison trace events")
Link: http://lore.kernel.org/r/e4f2716646918135ddbadf4146e92abb659de734.1700615159.git.alison.schofield@intel.com [1]
Cc: <stable@vger.kernel.org>
Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/cxl/core/hdm.c  |    3 +--
 drivers/cxl/core/port.c |    4 ++--
 2 files changed, 3 insertions(+), 4 deletions(-)

Comments

kernel test robot Dec. 7, 2023, 3:40 p.m. UTC | #1
Hi Dan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on v6.7-rc4 next-20231207]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Dan-Williams/cxl-hdm-Fix-dpa-translation-locking/20231207-115958
base:   linus/master
patch link:    https://lore.kernel.org/r/170192142664.461900.3169528633970716889.stgit%40dwillia2-xfh.jf.intel.com
patch subject: [PATCH] cxl/hdm: Fix dpa translation locking
config: i386-buildonly-randconfig-003-20231207 (https://download.01.org/0day-ci/archive/20231207/202312072350.QQTkSsY7-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231207/202312072350.QQTkSsY7-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202312072350.QQTkSsY7-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/cxl/core/port.c: In function 'dpa_resource_show':
>> drivers/cxl/core/port.c:231:37: warning: format '%llx' expects argument of type 'long long unsigned int', but argument 3 has type 'resource_size_t' {aka 'unsigned int'} [-Wformat=]
     231 |         return sysfs_emit(buf, "%#llx\n", cxl_dpa_resource_start(cxled));
         |                                 ~~~~^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
         |                                     |     |
         |                                     |     resource_size_t {aka unsigned int}
         |                                     long long unsigned int
         |                                 %#x


vim +231 drivers/cxl/core/port.c

   224	
   225	static ssize_t dpa_resource_show(struct device *dev, struct device_attribute *attr,
   226				    char *buf)
   227	{
   228		struct cxl_endpoint_decoder *cxled = to_cxl_endpoint_decoder(dev);
   229	
   230		guard(rwsem_read)(&cxl_dpa_rwsem);
 > 231		return sysfs_emit(buf, "%#llx\n", cxl_dpa_resource_start(cxled));
   232	}
   233	static DEVICE_ATTR_RO(dpa_resource);
   234
Dave Jiang Dec. 7, 2023, 3:46 p.m. UTC | #2
On 12/6/23 20:57, Dan Williams wrote:
> The helper, cxl_dpa_resource_start(), snapshots the dpa-address of an
> endpoint-decoder after acquiring the cxl_dpa_rwsem. However, it is
> sufficient to assert that cxl_dpa_rwsem is held rather than acquire it
> in the helper. Otherwise, it triggers multiple lockdep reports:
> 
> 1/ Tracing callbacks are in an atomic context that can not acquire sleeping
> locks:
> 
>     BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1525
>     in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1288, name: bash
>     preempt_count: 2, expected: 0
>     RCU nest depth: 0, expected: 0
>     [..]
>     Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20230524-3.fc38 05/24/2023
>     Call Trace:
>      <TASK>
>      dump_stack_lvl+0x71/0x90
>      __might_resched+0x1b2/0x2c0
>      down_read+0x1a/0x190
>      cxl_dpa_resource_start+0x15/0x50 [cxl_core]
>      cxl_trace_hpa+0x122/0x300 [cxl_core]
>      trace_event_raw_event_cxl_poison+0x1c9/0x2d0 [cxl_core]
> 
> 2/ The rwsem is already held in the inject poison path:
> 
>     WARNING: possible recursive locking detected
>     6.7.0-rc2+ #12 Tainted: G        W  OE    N
>     --------------------------------------------
>     bash/1288 is trying to acquire lock:
>     ffffffffc05f73d0 (cxl_dpa_rwsem){++++}-{3:3}, at: cxl_dpa_resource_start+0x15/0x50 [cxl_core]
> 
>     but task is already holding lock:
>     ffffffffc05f73d0 (cxl_dpa_rwsem){++++}-{3:3}, at: cxl_inject_poison+0x7d/0x1e0 [cxl_core]
>     [..]
>     Call Trace:
>      <TASK>
>      dump_stack_lvl+0x71/0x90
>      __might_resched+0x1b2/0x2c0
>      down_read+0x1a/0x190
>      cxl_dpa_resource_start+0x15/0x50 [cxl_core]
>      cxl_trace_hpa+0x122/0x300 [cxl_core]
>      trace_event_raw_event_cxl_poison+0x1c9/0x2d0 [cxl_core]
>      __traceiter_cxl_poison+0x5c/0x80 [cxl_core]
>      cxl_inject_poison+0x1bc/0x1e0 [cxl_core]
> 
> This appears to have been an issue since the initial implementation and
> uncovered by the new cxl-poison.sh test [1]. That test is now passing with
> these changes.
> 
> Fixes: 28a3ae4ff66c ("cxl/trace: Add an HPA to cxl_poison trace events")
> Link: http://lore.kernel.org/r/e4f2716646918135ddbadf4146e92abb659de734.1700615159.git.alison.schofield@intel.com [1]
> Cc: <stable@vger.kernel.org>
> Cc: Alison Schofield <alison.schofield@intel.com>
> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> ---
>  drivers/cxl/core/hdm.c  |    3 +--
>  drivers/cxl/core/port.c |    4 ++--
>  2 files changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 529baa8a1759..7d97790b893d 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -363,10 +363,9 @@ resource_size_t cxl_dpa_resource_start(struct cxl_endpoint_decoder *cxled)
>  {
>  	resource_size_t base = -1;
>  
> -	down_read(&cxl_dpa_rwsem);
> +	lockdep_assert_held(&cxl_dpa_rwsem);
>  	if (cxled->dpa_res)
>  		base = cxled->dpa_res->start;
> -	up_read(&cxl_dpa_rwsem);
>  
>  	return base;
>  }
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index 38441634e4c6..f6e9b2986a9a 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -226,9 +226,9 @@ static ssize_t dpa_resource_show(struct device *dev, struct device_attribute *at
>  			    char *buf)
>  {
>  	struct cxl_endpoint_decoder *cxled = to_cxl_endpoint_decoder(dev);
> -	u64 base = cxl_dpa_resource_start(cxled);
>  
> -	return sysfs_emit(buf, "%#llx\n", base);
> +	guard(rwsem_read)(&cxl_dpa_rwsem);
> +	return sysfs_emit(buf, "%#llx\n", cxl_dpa_resource_start(cxled));
>  }
>  static DEVICE_ATTR_RO(dpa_resource);
>  
>
kernel test robot Dec. 7, 2023, 4:13 p.m. UTC | #3
Hi Dan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on v6.7-rc4 next-20231207]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Dan-Williams/cxl-hdm-Fix-dpa-translation-locking/20231207-115958
base:   linus/master
patch link:    https://lore.kernel.org/r/170192142664.461900.3169528633970716889.stgit%40dwillia2-xfh.jf.intel.com
patch subject: [PATCH] cxl/hdm: Fix dpa translation locking
config: i386-allmodconfig (https://download.01.org/0day-ci/archive/20231208/202312080021.eQEtUpnB-lkp@intel.com/config)
compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231208/202312080021.eQEtUpnB-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202312080021.eQEtUpnB-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/cxl/core/port.c:231:36: warning: format specifies type 'unsigned long long' but the argument has type 'resource_size_t' (aka 'unsigned int') [-Wformat]
           return sysfs_emit(buf, "%#llx\n", cxl_dpa_resource_start(cxled));
                                   ~~~~~     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                                   %#x
   1 warning generated.


vim +231 drivers/cxl/core/port.c

   224	
   225	static ssize_t dpa_resource_show(struct device *dev, struct device_attribute *attr,
   226				    char *buf)
   227	{
   228		struct cxl_endpoint_decoder *cxled = to_cxl_endpoint_decoder(dev);
   229	
   230		guard(rwsem_read)(&cxl_dpa_rwsem);
 > 231		return sysfs_emit(buf, "%#llx\n", cxl_dpa_resource_start(cxled));
   232	}
   233	static DEVICE_ATTR_RO(dpa_resource);
   234
Jonathan Cameron Dec. 19, 2023, 4:49 p.m. UTC | #4
On Wed, 06 Dec 2023 19:57:06 -0800
Dan Williams <dan.j.williams@intel.com> wrote:

> The helper, cxl_dpa_resource_start(), snapshots the dpa-address of an
> endpoint-decoder after acquiring the cxl_dpa_rwsem. However, it is
> sufficient to assert that cxl_dpa_rwsem is held rather than acquire it
> in the helper. Otherwise, it triggers multiple lockdep reports:
> 
> 1/ Tracing callbacks are in an atomic context that can not acquire sleeping
> locks:
> 
>     BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1525
>     in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1288, name: bash
>     preempt_count: 2, expected: 0
>     RCU nest depth: 0, expected: 0
>     [..]
>     Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20230524-3.fc38 05/24/2023
>     Call Trace:
>      <TASK>
>      dump_stack_lvl+0x71/0x90
>      __might_resched+0x1b2/0x2c0
>      down_read+0x1a/0x190
>      cxl_dpa_resource_start+0x15/0x50 [cxl_core]
>      cxl_trace_hpa+0x122/0x300 [cxl_core]
>      trace_event_raw_event_cxl_poison+0x1c9/0x2d0 [cxl_core]
> 
> 2/ The rwsem is already held in the inject poison path:
> 
>     WARNING: possible recursive locking detected
>     6.7.0-rc2+ #12 Tainted: G        W  OE    N
>     --------------------------------------------
>     bash/1288 is trying to acquire lock:
>     ffffffffc05f73d0 (cxl_dpa_rwsem){++++}-{3:3}, at: cxl_dpa_resource_start+0x15/0x50 [cxl_core]
> 
>     but task is already holding lock:
>     ffffffffc05f73d0 (cxl_dpa_rwsem){++++}-{3:3}, at: cxl_inject_poison+0x7d/0x1e0 [cxl_core]
>     [..]
>     Call Trace:
>      <TASK>
>      dump_stack_lvl+0x71/0x90
>      __might_resched+0x1b2/0x2c0
>      down_read+0x1a/0x190
>      cxl_dpa_resource_start+0x15/0x50 [cxl_core]
>      cxl_trace_hpa+0x122/0x300 [cxl_core]
>      trace_event_raw_event_cxl_poison+0x1c9/0x2d0 [cxl_core]
>      __traceiter_cxl_poison+0x5c/0x80 [cxl_core]
>      cxl_inject_poison+0x1bc/0x1e0 [cxl_core]
> 
> This appears to have been an issue since the initial implementation and
> uncovered by the new cxl-poison.sh test [1]. That test is now passing with
> these changes.
> 
> Fixes: 28a3ae4ff66c ("cxl/trace: Add an HPA to cxl_poison trace events")
> Link: http://lore.kernel.org/r/e4f2716646918135ddbadf4146e92abb659de734.1700615159.git.alison.schofield@intel.com [1]
> Cc: <stable@vger.kernel.org>
> Cc: Alison Schofield <alison.schofield@intel.com>
> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Seems good other than %#pa being more appropriate for the printk.
I'm guessing you already tidied that up though.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  drivers/cxl/core/hdm.c  |    3 +--
>  drivers/cxl/core/port.c |    4 ++--
>  2 files changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 529baa8a1759..7d97790b893d 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -363,10 +363,9 @@ resource_size_t cxl_dpa_resource_start(struct cxl_endpoint_decoder *cxled)
>  {
>  	resource_size_t base = -1;
>  
> -	down_read(&cxl_dpa_rwsem);
> +	lockdep_assert_held(&cxl_dpa_rwsem);
>  	if (cxled->dpa_res)
>  		base = cxled->dpa_res->start;
> -	up_read(&cxl_dpa_rwsem);
>  
>  	return base;
>  }
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index 38441634e4c6..f6e9b2986a9a 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -226,9 +226,9 @@ static ssize_t dpa_resource_show(struct device *dev, struct device_attribute *at
>  			    char *buf)
>  {
>  	struct cxl_endpoint_decoder *cxled = to_cxl_endpoint_decoder(dev);
> -	u64 base = cxl_dpa_resource_start(cxled);
>  
> -	return sysfs_emit(buf, "%#llx\n", base);
> +	guard(rwsem_read)(&cxl_dpa_rwsem);
> +	return sysfs_emit(buf, "%#llx\n", cxl_dpa_resource_start(cxled));
>  }
>  static DEVICE_ATTR_RO(dpa_resource);
>  
>
Fan Ni Dec. 19, 2023, 6:14 p.m. UTC | #5
On Wed, Dec 06, 2023 at 07:57:06PM -0800, Dan Williams wrote:
> The helper, cxl_dpa_resource_start(), snapshots the dpa-address of an
> endpoint-decoder after acquiring the cxl_dpa_rwsem. However, it is
> sufficient to assert that cxl_dpa_rwsem is held rather than acquire it
> in the helper. Otherwise, it triggers multiple lockdep reports:
> 
> 1/ Tracing callbacks are in an atomic context that can not acquire sleeping
> locks:
> 
>     BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1525
>     in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1288, name: bash
>     preempt_count: 2, expected: 0
>     RCU nest depth: 0, expected: 0
>     [..]
>     Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20230524-3.fc38 05/24/2023
>     Call Trace:
>      <TASK>
>      dump_stack_lvl+0x71/0x90
>      __might_resched+0x1b2/0x2c0
>      down_read+0x1a/0x190
>      cxl_dpa_resource_start+0x15/0x50 [cxl_core]
>      cxl_trace_hpa+0x122/0x300 [cxl_core]
>      trace_event_raw_event_cxl_poison+0x1c9/0x2d0 [cxl_core]
> 
> 2/ The rwsem is already held in the inject poison path:
> 
>     WARNING: possible recursive locking detected
>     6.7.0-rc2+ #12 Tainted: G        W  OE    N
>     --------------------------------------------
>     bash/1288 is trying to acquire lock:
>     ffffffffc05f73d0 (cxl_dpa_rwsem){++++}-{3:3}, at: cxl_dpa_resource_start+0x15/0x50 [cxl_core]
> 
>     but task is already holding lock:
>     ffffffffc05f73d0 (cxl_dpa_rwsem){++++}-{3:3}, at: cxl_inject_poison+0x7d/0x1e0 [cxl_core]
>     [..]
>     Call Trace:
>      <TASK>
>      dump_stack_lvl+0x71/0x90
>      __might_resched+0x1b2/0x2c0
>      down_read+0x1a/0x190
>      cxl_dpa_resource_start+0x15/0x50 [cxl_core]
>      cxl_trace_hpa+0x122/0x300 [cxl_core]
>      trace_event_raw_event_cxl_poison+0x1c9/0x2d0 [cxl_core]
>      __traceiter_cxl_poison+0x5c/0x80 [cxl_core]
>      cxl_inject_poison+0x1bc/0x1e0 [cxl_core]
> 
> This appears to have been an issue since the initial implementation and
> uncovered by the new cxl-poison.sh test [1]. That test is now passing with
> these changes.
> 
> Fixes: 28a3ae4ff66c ("cxl/trace: Add an HPA to cxl_poison trace events")
> Link: http://lore.kernel.org/r/e4f2716646918135ddbadf4146e92abb659de734.1700615159.git.alison.schofield@intel.com [1]
> Cc: <stable@vger.kernel.org>
> Cc: Alison Schofield <alison.schofield@intel.com>
> Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---

Reviewed-by: Fan Ni <fan.ni@samsung.com>

>  drivers/cxl/core/hdm.c  |    3 +--
>  drivers/cxl/core/port.c |    4 ++--
>  2 files changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 529baa8a1759..7d97790b893d 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -363,10 +363,9 @@ resource_size_t cxl_dpa_resource_start(struct cxl_endpoint_decoder *cxled)
>  {
>  	resource_size_t base = -1;
>  
> -	down_read(&cxl_dpa_rwsem);
> +	lockdep_assert_held(&cxl_dpa_rwsem);
>  	if (cxled->dpa_res)
>  		base = cxled->dpa_res->start;
> -	up_read(&cxl_dpa_rwsem);
>  
>  	return base;
>  }
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index 38441634e4c6..f6e9b2986a9a 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -226,9 +226,9 @@ static ssize_t dpa_resource_show(struct device *dev, struct device_attribute *at
>  			    char *buf)
>  {
>  	struct cxl_endpoint_decoder *cxled = to_cxl_endpoint_decoder(dev);
> -	u64 base = cxl_dpa_resource_start(cxled);
>  
> -	return sysfs_emit(buf, "%#llx\n", base);
> +	guard(rwsem_read)(&cxl_dpa_rwsem);
> +	return sysfs_emit(buf, "%#llx\n", cxl_dpa_resource_start(cxled));
>  }
>  static DEVICE_ATTR_RO(dpa_resource);
>  
>
diff mbox series

Patch

diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index 529baa8a1759..7d97790b893d 100644
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -363,10 +363,9 @@  resource_size_t cxl_dpa_resource_start(struct cxl_endpoint_decoder *cxled)
 {
 	resource_size_t base = -1;
 
-	down_read(&cxl_dpa_rwsem);
+	lockdep_assert_held(&cxl_dpa_rwsem);
 	if (cxled->dpa_res)
 		base = cxled->dpa_res->start;
-	up_read(&cxl_dpa_rwsem);
 
 	return base;
 }
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 38441634e4c6..f6e9b2986a9a 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -226,9 +226,9 @@  static ssize_t dpa_resource_show(struct device *dev, struct device_attribute *at
 			    char *buf)
 {
 	struct cxl_endpoint_decoder *cxled = to_cxl_endpoint_decoder(dev);
-	u64 base = cxl_dpa_resource_start(cxled);
 
-	return sysfs_emit(buf, "%#llx\n", base);
+	guard(rwsem_read)(&cxl_dpa_rwsem);
+	return sysfs_emit(buf, "%#llx\n", cxl_dpa_resource_start(cxled));
 }
 static DEVICE_ATTR_RO(dpa_resource);