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

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

2015-08-31 Thread Vitaly Kuznetsov
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 small. This is just a part of the fix: serial8250_console_write()

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

2015-08-31 Thread Vitaly Kuznetsov
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 small. This is just a part of the fix: serial8250_console_write()