From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 763871A09F0 for ; Tue, 20 Jan 2015 20:28:31 +1100 (AEDT) Message-ID: <1421746096.4949.40.camel@kernel.crashing.org> Subject: Re: [PATCH] powerpc/pseries: Avoid context switch in EEH reset if required From: Benjamin Herrenschmidt To: Gavin Shan Date: Tue, 20 Jan 2015 10:28:16 +0100 In-Reply-To: <1421621243-21265-1-git-send-email-gwshan@linux.vnet.ibm.com> References: <1421621243-21265-1-git-send-email-gwshan@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 2015-01-19 at 09:47 +1100, Gavin Shan wrote: > On pseries platform, the EEH reset backend pseries_eeh_reset() can > be called in atomic context as follows. For this case, we should > call udelay() instead of msleep() to avoid context switching. > > drivers/scsi/ipr.c::ipr_reset_slot_reset_done() > drivers/pci/pci.c::pci_set_pcie_reset_state() > arch/powerpc/kernel/eeh.c::pcibios_set_pcie_reset_state() > arch/powerpc/platforms/pseries/eeh_pseries.c::pseries_eeh_reset() It's not acceptable to introduce multi-millisecond delays at interrupt time. In fact, we should generally not use udelay in such context. I understand that this is an exceptional error handling case but it's still not right. Are there many other users of pci_set_pcie_reset_state() at interrupt time ? Can we have a discussion with the PCI folks as to whether that should be legal or not ? I'm tempted to require that it's made illegal. Ben. > Signed-off-by: Gavin Shan > Tested-by: Wen Xiong > --- > arch/powerpc/platforms/pseries/eeh_pseries.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/arch/powerpc/platforms/pseries/eeh_pseries.c b/arch/powerpc/platforms/pseries/eeh_pseries.c > index a6c7e19..67623a3 100644 > --- a/arch/powerpc/platforms/pseries/eeh_pseries.c > +++ b/arch/powerpc/platforms/pseries/eeh_pseries.c > @@ -503,8 +503,7 @@ static int pseries_eeh_get_state(struct eeh_pe *pe, int *state) > */ > static int pseries_eeh_reset(struct eeh_pe *pe, int option) > { > - int config_addr; > - int ret; > + int config_addr, delay, ret; > > /* Figure out PE address */ > config_addr = pe->config_addr; > @@ -528,9 +527,14 @@ static int pseries_eeh_reset(struct eeh_pe *pe, int option) > /* We need reset hold or settlement delay */ > if (option == EEH_RESET_FUNDAMENTAL || > option == EEH_RESET_HOT) > - msleep(EEH_PE_RST_HOLD_TIME); > + delay = EEH_PE_RST_HOLD_TIME; > + else > + delay = EEH_PE_RST_SETTLE_TIME; > + > + if (in_atomic()) > + udelay(delay * 1000); > else > - msleep(EEH_PE_RST_SETTLE_TIME); > + msleep(delay); > > return ret; > }