| Message ID | 20211117025956.79616-3-dave@stgolabs.net (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | scsi/fcoe: Play nicer with PREEMPT_RT | expand |
On 2021-11-16 18:59:55 [-0800], Davidlohr Bueso wrote: > 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> Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Sebastian
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; }; /**
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(-)