From: Bob Pearson <rpearsonhpe@xxxxxxxxx> [ Upstream commit eff6d998ca297cb0b2e53b032a56cf8e04dd8b17 ] 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@xxxxxxxxx Signed-off-by: Bob Pearson <rpearsonhpe@xxxxxxxxx> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- drivers/infiniband/sw/rxe/rxe_param.h | 6 ++++++ drivers/infiniband/sw/rxe/rxe_task.c | 16 ++++++++++++---- 2 files changed, 18 insertions(+), 4 deletions(-) diff --git a/drivers/infiniband/sw/rxe/rxe_param.h b/drivers/infiniband/sw/rxe/rxe_param.h index 918270e34a35..4d85c9496a95 100644 --- a/drivers/infiniband/sw/rxe/rxe_param.h +++ b/drivers/infiniband/sw/rxe/rxe_param.h @@ -107,6 +107,12 @@ 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, diff --git a/drivers/infiniband/sw/rxe/rxe_task.c b/drivers/infiniband/sw/rxe/rxe_task.c index 0c4db5bb17d7..2248cf33d776 100644 --- a/drivers/infiniband/sw/rxe/rxe_task.c +++ b/drivers/infiniband/sw/rxe/rxe_task.c @@ -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 */ -- 2.35.1
