From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753884AbcHUPco (ORCPT ); Sun, 21 Aug 2016 11:32:44 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:55370 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753689AbcHUPcj (ORCPT ); Sun, 21 Aug 2016 11:32:39 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Raghava Aditya Renukunta , "Martin K . Petersen" , Willy Tarreau Subject: [PATCH 3.10 063/180] aacraid: Relinquish CPU during timeout wait Date: Sun, 21 Aug 2016 17:29:53 +0200 Message-Id: <1471793510-13022-64-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1471793510-13022-1-git-send-email-w@1wt.eu> References: <1471793510-13022-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Raghava Aditya Renukunta 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()" Cc: stable@vger.kernel.org Signed-off-by: Raghava Aditya Renukunta Reviewed-by: Johannes Thumshirn Signed-off-by: Martin K. Petersen Signed-off-by: Willy Tarreau --- drivers/scsi/aacraid/commsup.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/scsi/aacraid/commsup.c b/drivers/scsi/aacraid/commsup.c index 6a0d362..addcd58 100644 --- a/drivers/scsi/aacraid/commsup.c +++ b/drivers/scsi/aacraid/commsup.c @@ -590,10 +590,10 @@ int aac_fib_send(u16 command, struct fib *fibptr, unsigned long size, } 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 -- 2.8.0.rc2.1.gbe9624a