Commit 848b8977 authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Martin K. Petersen
Browse files

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: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarDavidlohr Bueso <dave@stgolabs.net>
Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 0873fe44

drivers/scsi/fcoe/fcoe.c

+4 −2
Original line number Diff line number Diff line
@@ -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 */

include/scsi/libfcoe.h

+2 −0
Original line number Diff line number Diff line
@@ -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;

};



/**