lkml.org 
[lkml]   [2021]   [Nov]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 2/3] scsi/fcoe: Add a local_lock to fcoe_percpu
Date
fcoe_get_paged_crc_eof() relies on the caller having preemption
disabled to ensure the per-CPU fcoe_percpu context remains valid
throughout the call. This is done by either holding spinlocks
(such as bnx2fc_global_lock or qedf_global_lock) or the get_cpu()
from fcoe_alloc_paged_crc_eof(). This last one breaks PREEMPT_RT
semantics as there can be memory allocation and end up sleeping
in atomic contexts.

Introduce a local_lock_t to struct fcoe_percpu that will keep the
non-RT case the same, mapping to preempt_disable/enable, while
RT will use a per-CPU spinlock allowing the region to be preemptible
but still maintain CPU locality. The other users of fcoe_percpu
are already safe in this regard and do not require local_lock()ing.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
drivers/scsi/fcoe/fcoe.c | 6 ++++--
include/scsi/libfcoe.h | 2 ++
2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c
index 6415f88738ad..a0064a1b4a32 100644
--- a/drivers/scsi/fcoe/fcoe.c
+++ b/drivers/scsi/fcoe/fcoe.c
@@ -1452,9 +1452,10 @@ static int fcoe_alloc_paged_crc_eof(struct sk_buff *skb, int tlen)
struct fcoe_percpu_s *fps;
int rc;

- fps = &get_cpu_var(fcoe_percpu);
+ local_lock(&fcoe_percpu.lock);
+ fps = this_cpu_ptr(&fcoe_percpu);
rc = fcoe_get_paged_crc_eof(skb, tlen, fps);
- put_cpu_var(fcoe_percpu);
+ local_unlock(&fcoe_percpu.lock);

return rc;
}
@@ -2487,6 +2488,7 @@ static int __init fcoe_init(void)
p = per_cpu_ptr(&fcoe_percpu, cpu);
INIT_WORK(&p->work, fcoe_receive_work);
skb_queue_head_init(&p->fcoe_rx_list);
+ local_lock_init(&p->lock);
}

/* Setup link change notification */
diff --git a/include/scsi/libfcoe.h b/include/scsi/libfcoe.h
index fac8e89aed81..6e79fb87fea2 100644
--- a/include/scsi/libfcoe.h
+++ b/include/scsi/libfcoe.h
@@ -14,6 +14,7 @@
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/workqueue.h>
+#include <linux/local_lock.h>
#include <linux/random.h>
#include <scsi/fc/fc_fcoe.h>
#include <scsi/libfc.h>
@@ -326,6 +327,7 @@ struct fcoe_percpu_s {
struct sk_buff_head fcoe_rx_list;
struct page *crc_eof_page;
int crc_eof_offset;
+ local_lock_t lock;
};

/**
--
2.26.2
\
 
 \ /
  Last update: 2021-11-17 04:01    [W:0.082 / U:1.832 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site