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scsi: fcoe: Add a local_lock to fcoe_percpu 

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.

Link: https://lore.kernel.org/r/20211117025956.79616-3-dave@stgolabs.net
Link: https://lore.kernel.org/r/20220506105758.283887-2-bigeasy@linutronix.de
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Davidlohr Bueso 2022-05-06 12:57:55 +02:00 committed by Martin K. Petersen
parent 0873fe44e7
commit 848b89778e
2 changed files with 6 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/scsi/fcoe/fcoe.c
View File

@ -1453,9 +1453,10 @@ 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;
}
@ -2488,6 +2489,7 @@ 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 */

2
include/scsi/libfcoe.h
View File

@ -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;
};
/**