Commit eff6d998 authored by Bob Pearson's avatar Bob Pearson Committed by Jason Gunthorpe
Browse files

RDMA/rxe: Limit the number of calls to each tasklet 

Limit the maximum number of calls to each tasklet from rxe_do_task()
before yielding the cpu. When the limit is reached reschedule the tasklet
and exit the calling loop. This patch prevents one tasklet from consuming
100% of a cpu core and causing a deadlock or soft lockup.

Link: https://lore.kernel.org/r/20220630190425.2251-9-rpearsonhpe@gmail.com


Signed-off-by: default avatarBob Pearson <rpearsonhpe@gmail.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
parent 8bb143c5

drivers/infiniband/sw/rxe/rxe_param.h

+6 −0
Original line number Diff line number Diff line
@@ -105,6 +105,12 @@ enum rxe_device_param { 
	RXE_INFLIGHT_SKBS_PER_QP_HIGH	= 64,

	RXE_INFLIGHT_SKBS_PER_QP_LOW	= 16,



	/* Max number of interations of each tasklet

	 * before yielding the cpu to let other

	 * work make progress

	 */

	RXE_MAX_ITERATIONS		= 1024,



	/* Delay before calling arbiter timer */

	RXE_NSEC_ARB_TIMER_DELAY	= 200,

drivers/infiniband/sw/rxe/rxe_task.c

+12 −4
Original line number Diff line number Diff line
@@ -8,7 +8,7 @@ 
#include <linux/interrupt.h>

#include <linux/hardirq.h>



#include "rxe_task.h"

#include "rxe.h"



int __rxe_do_task(struct rxe_task *task)
@@ -33,6 +33,7 @@ void rxe_do_task(struct tasklet_struct *t) 
	int cont;

	int ret;

	struct rxe_task *task = from_tasklet(task, t, tasklet);

	unsigned int iterations = RXE_MAX_ITERATIONS;



	spin_lock_bh(&task->state_lock);

	switch (task->state) {
@@ -61,13 +62,20 @@ void rxe_do_task(struct tasklet_struct *t) 
		spin_lock_bh(&task->state_lock);

		switch (task->state) {

		case TASK_STATE_BUSY:

			if (ret)

			if (ret) {

				task->state = TASK_STATE_START;

			else

			} else if (iterations--) {

				cont = 1;

			} else {

				/* reschedule the tasklet and exit

				 * the loop to give up the cpu

				 */

				tasklet_schedule(&task->tasklet);

				task->state = TASK_STATE_START;

			}

			break;



		/* soneone tried to run the task since the last time we called

		/* someone tried to run the task since the last time we called

		 * func, so we will call one more time regardless of the

		 * return value

		 */