From: "Tomáš Glozar" <tglozar@gmail.com>
To: nvdimm@lists.linux.dev
Cc: dan.j.williams@intel.com, vishal.l.verma@intel.com,
dave.jiang@intel.com, ira.weiny@intel.com,
linux-kernel@vger.kernel.org, Tomas Glozar <tglozar@redhat.com>
Subject: [PATCH] nd_btt: Make BTT lanes preemptible
Date: Tue, 12 Sep 2023 10:24:40 +0200 [thread overview]
Message-ID: <20230912082440.325189-1-tglozar@gmail.com> (raw)
From: Tomas Glozar <tglozar@redhat.com>
nd_region_acquire_lane uses get_cpu, which disables preemption. This is
an issue on PREEMPT_RT kernels, since btt_write_pg and also
nd_region_acquire_lane itself take a spin lock, resulting in BUG:
sleeping function called from invalid context.
Fix the issue by replacing get_cpu with smp_process_id and
migrate_disable when needed. This makes BTT operations preemptible, thus
permitting the use of spin_lock.
Fixes: 5212e11fde4d ("nd_btt: atomic sector updates")
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
---
drivers/nvdimm/region_devs.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index 0a81f87f6f6c..e2f1fb99707f 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -939,7 +939,8 @@ unsigned int nd_region_acquire_lane(struct nd_region *nd_region)
{
unsigned int cpu, lane;
- cpu = get_cpu();
+ migrate_disable();
+ cpu = smp_processor_id();
if (nd_region->num_lanes < nr_cpu_ids) {
struct nd_percpu_lane *ndl_lock, *ndl_count;
@@ -958,16 +959,15 @@ EXPORT_SYMBOL(nd_region_acquire_lane);
void nd_region_release_lane(struct nd_region *nd_region, unsigned int lane)
{
if (nd_region->num_lanes < nr_cpu_ids) {
- unsigned int cpu = get_cpu();
+ unsigned int cpu = smp_processor_id();
struct nd_percpu_lane *ndl_lock, *ndl_count;
ndl_count = per_cpu_ptr(nd_region->lane, cpu);
ndl_lock = per_cpu_ptr(nd_region->lane, lane);
if (--ndl_count->count == 0)
spin_unlock(&ndl_lock->lock);
- put_cpu();
}
- put_cpu();
+ migrate_enable();
}
EXPORT_SYMBOL(nd_region_release_lane);
--
2.39.3
next reply other threads:[~2023-09-12 8:31 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-12 8:24 Tomáš Glozar [this message]
2023-09-14 20:17 ` [PATCH] nd_btt: Make BTT lanes preemptible Ira Weiny
2023-09-18 5:47 ` Tomas Glozar
2023-09-18 21:32 ` Ira Weiny
2023-09-20 5:42 ` Tomas Glozar
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