The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b6d57e24ce6cc3df8a8845e1b193e88a65d501b1 Mon Sep 17 00:00:00 2001

From: Mike Marciniszyn mike.marciniszyn@cornelisnetworks.com Date: Mon, 29 Nov 2021 14:19:58 -0500 Subject: [PATCH] IB/hfi1: Insure use of smp_processor_id() is preempt disabled

The following BUG has just surfaced with our 5.16 testing:

BUG: using smp_processor_id() in preemptible [00000000] code: mpicheck/1581081 caller is sdma_select_user_engine+0x72/0x210 [hfi1] CPU: 0 PID: 1581081 Comm: mpicheck Tainted: G S 5.16.0-rc1+ #1 Hardware name: Intel Corporation S2600WT2R/S2600WT2R, BIOS SE5C610.86B.01.01.0016.033120161139 03/31/2016 Call Trace: <TASK> dump_stack_lvl+0x33/0x42 check_preemption_disabled+0xbf/0xe0 sdma_select_user_engine+0x72/0x210 [hfi1] ? _raw_spin_unlock_irqrestore+0x1f/0x31 ? hfi1_mmu_rb_insert+0x6b/0x200 [hfi1] hfi1_user_sdma_process_request+0xa02/0x1120 [hfi1] ? hfi1_write_iter+0xb8/0x200 [hfi1] hfi1_write_iter+0xb8/0x200 [hfi1] do_iter_readv_writev+0x163/0x1c0 do_iter_write+0x80/0x1c0 vfs_writev+0x88/0x1a0 ? recalibrate_cpu_khz+0x10/0x10 ? ktime_get+0x3e/0xa0 ? __fget_files+0x66/0xa0 do_writev+0x65/0x100 do_syscall_64+0x3a/0x80

Fix this long standing bug by moving the smp_processor_id() to after the rcu_read_lock().

The rcu_read_lock() implicitly disables preemption.

Link: https://lore.kernel.org/r/20211129191958.101968.87329.stgit@awfm-01.cornelis... Cc: stable@vger.kernel.org Fixes: 0cb2aa690c7e ("IB/hfi1: Add sysfs interface for affinity setup") Signed-off-by: Mike Marciniszyn mike.marciniszyn@cornelisnetworks.com Signed-off-by: Dennis Dalessandro dennis.dalessandro@cornelisnetworks.com Signed-off-by: Jason Gunthorpe jgg@nvidia.com

diff --git a/drivers/infiniband/hw/hfi1/sdma.c b/drivers/infiniband/hw/hfi1/sdma.c index 2b6c24b7b586..f07d328689d3 100644 --- a/drivers/infiniband/hw/hfi1/sdma.c +++ b/drivers/infiniband/hw/hfi1/sdma.c @@ -838,8 +838,8 @@ struct sdma_engine *sdma_select_user_engine(struct hfi1_devdata *dd, if (current->nr_cpus_allowed != 1) goto out;

- cpu_id = smp_processor_id(); rcu_read_lock(); + cpu_id = smp_processor_id(); rht_node = rhashtable_lookup(dd->sdma_rht, &cpu_id, sdma_rht_params);