Patch "aacraid: Relinquish CPU during timeout wait" has been added to the 4.5-stable tree

This is a note to let you know that I've just added the patch titled

aacraid: Relinquish CPU during timeout wait

to the 4.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
aacraid-relinquish-cpu-during-timeout-wait.patch
and it can be found in the queue-4.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Raghava Aditya Renukunta <[email protected]>
Date: Mon, 25 Apr 2016 23:31:26 -0700
Subject: aacraid: Relinquish CPU during timeout wait

From: Raghava Aditya Renukunta <[email protected]>

commit 07beca2be24cc710461c0b131832524c9ee08910 upstream.

aac_fib_send has a special function case for initial commands during driver initialization using wait < 0(pseudo sync mode). In this case, the command does not sleep but rather spins checking for timeout.This loop is calls cpu_relax() in an attempt to allow other processes/threads to use the CPU, but this function does not relinquish the CPU and so the command will hog the processor. This was observed in a KDUMP "crashkernel" and that prevented the "command thread" (which is responsible for completing the command from being timed out) from starting because it could not get the CPU.

Fixed by replacing "cpu_relax()" call with "schedule()"

---
 drivers/scsi/aacraid/commsup.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

@@ -611,10 +611,10 @@ int aac_fib_send(u16 command, struct fib
 					}
 					return -EFAULT;
 				}
-				/* We used to udelay() here but that absorbed
-				 * a CPU when a timeout occured. Not very
-				 * useful. */
-				cpu_relax();
+				/*
+				 * Allow other processes / CPUS to use core
+				 */
+				schedule();
 			}
 		} else if (down_interruptible(&fibptr->event_wait)) {
 			/* Do nothing ... satisfy

Patches currently in stable-queue which might be from [email protected] are

queue-4.5/aacraid-fix-for-kdump-driver-hang.patch queue-4.5/aacraid-fix-for-aac_command_thread-hang.patch queue-4.5/aacraid-relinquish-cpu-during-timeout-wait.patch