RE: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-06 Thread KY Srinivasan
> -Original Message- > From: Dexuan Cui > Sent: Sunday, September 6, 2015 4:48 AM > To: Greg Kroah-Hartman ; Vitaly Kuznetsov > > Cc: Jiri Slaby ; linux-ser...@vger.kernel.org; linux- > ker...@vger.kernel.org; KY Srinivasan ; Peter Hurley > > Subject: RE: [P

RE: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-06 Thread Dexuan Cui
> -Original Message- > From: Greg Kroah-Hartman > Sent: Saturday, September 5, 2015 0:10 > On Fri, Sep 04, 2015 at 09:19:38AM +0200, Vitaly Kuznetsov wrote: > > Greg Kroah-Hartman writes: > > > > > On Mon, Aug 31, 2015 at 04:34:16PM +0200, Vitaly Kuznetsov wrote: > > >> Hyper-V serial port

RE: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-06 Thread Dexuan Cui
> -Original Message- > From: Greg Kroah-Hartman > Sent: Saturday, September 5, 2015 0:10 > On Fri, Sep 04, 2015 at 09:19:38AM +0200, Vitaly Kuznetsov wrote: > > Greg Kroah-Hartman writes: > > > > > On Mon, Aug 31, 2015 at 04:34:16PM +0200, Vitaly Kuznetsov wrote: > > >> Hyper-V serial port

RE: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-06 Thread KY Srinivasan
linux- > ker...@vger.kernel.org; KY Srinivasan <k...@microsoft.com>; Peter Hurley > <pe...@hurleysoftware.com> > Subject: RE: [PATCH] serial: core: prevent softlockups on slow consoles > > > -Original Message- > > From: Greg Kroah-Hartman > > Sent: Saturda

Re: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-04 Thread Greg Kroah-Hartman
On Fri, Sep 04, 2015 at 09:19:38AM +0200, Vitaly Kuznetsov wrote: > Greg Kroah-Hartman writes: > > > On Mon, Aug 31, 2015 at 04:34:16PM +0200, Vitaly Kuznetsov wrote: > >> Hyper-V serial port is very slow on multi-vCPU guest, this causes > >> soflockups on intensive console writes. Touch nmi

Re: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-04 Thread Peter Hurley
On 09/04/2015 03:19 AM, Vitaly Kuznetsov wrote: > Greg Kroah-Hartman writes: >> I don't like this, please narrow this down to the real problem that your >> hardware has here, the putchar function should not be this slow. If it >> is, something is wrong. > > I'm afraid this is really the case:

Re: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-04 Thread Vitaly Kuznetsov
Greg Kroah-Hartman writes: > On Mon, Aug 31, 2015 at 04:34:16PM +0200, Vitaly Kuznetsov wrote: >> Hyper-V serial port is very slow on multi-vCPU guest, this causes >> soflockups on intensive console writes. Touch nmi watchdog after putting >> every char on port to avoid the issue for all serial

Re: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-04 Thread Peter Hurley
On 09/04/2015 03:19 AM, Vitaly Kuznetsov wrote: > Greg Kroah-Hartman writes: >> I don't like this, please narrow this down to the real problem that your >> hardware has here, the putchar function should not be this slow. If it >> is, something is wrong. > > I'm

Re: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-04 Thread Greg Kroah-Hartman
On Fri, Sep 04, 2015 at 09:19:38AM +0200, Vitaly Kuznetsov wrote: > Greg Kroah-Hartman writes: > > > On Mon, Aug 31, 2015 at 04:34:16PM +0200, Vitaly Kuznetsov wrote: > >> Hyper-V serial port is very slow on multi-vCPU guest, this causes > >> soflockups on intensive

Re: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-04 Thread Vitaly Kuznetsov
Greg Kroah-Hartman writes: > On Mon, Aug 31, 2015 at 04:34:16PM +0200, Vitaly Kuznetsov wrote: >> Hyper-V serial port is very slow on multi-vCPU guest, this causes >> soflockups on intensive console writes. Touch nmi watchdog after putting >> every char on port to

Re: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-03 Thread Greg Kroah-Hartman
On Mon, Aug 31, 2015 at 04:34:16PM +0200, Vitaly Kuznetsov wrote: > Hyper-V serial port is very slow on multi-vCPU guest, this causes > soflockups on intensive console writes. Touch nmi watchdog after putting > every char on port to avoid the issue for all serial drivers, the overhead > should be

Re: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-03 Thread Greg Kroah-Hartman
On Mon, Aug 31, 2015 at 04:34:16PM +0200, Vitaly Kuznetsov wrote: > Hyper-V serial port is very slow on multi-vCPU guest, this causes > soflockups on intensive console writes. Touch nmi watchdog after putting > every char on port to avoid the issue for all serial drivers, the overhead > should be

Re: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-02 Thread Vitaly Kuznetsov
Peter Hurley writes: > Hi Vitaly, > > On 08/31/2015 10:34 AM, Vitaly Kuznetsov wrote: >> Hyper-V serial port is very slow on multi-vCPU guest > > How slow and why? > Not sure why, but here is a trace: 1) | serial8250_console_putchar() { 1) |

Re: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-02 Thread Peter Hurley
Hi Vitaly, On 08/31/2015 10:34 AM, Vitaly Kuznetsov wrote: > Hyper-V serial port is very slow on multi-vCPU guest How slow and why? > this causes > soflockups on intensive console writes. Touch nmi watchdog after putting > every char on port to avoid the issue for all serial drivers, the

Re: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-02 Thread Vitaly Kuznetsov
Peter Hurley writes: > Hi Vitaly, > > On 08/31/2015 10:34 AM, Vitaly Kuznetsov wrote: >> Hyper-V serial port is very slow on multi-vCPU guest > > How slow and why? > Not sure why, but here is a trace: 1) |

Re: [PATCH] serial: core: prevent softlockups on slow consoles

2015-09-02 Thread Peter Hurley
Hi Vitaly, On 08/31/2015 10:34 AM, Vitaly Kuznetsov wrote: > Hyper-V serial port is very slow on multi-vCPU guest How slow and why? > this causes > soflockups on intensive console writes. Touch nmi watchdog after putting > every char on port to avoid the issue for all serial drivers, the