Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Mon, Oct 12, 2015 at 09:09:24PM +0800, Boqun Feng wrote: > On Mon, Oct 12, 2015 at 01:54:38PM +0200, Peter Zijlstra wrote: > > On Mon, Oct 12, 2015 at 05:06:36PM +0800, Boqun Feng wrote: > > > Understood. > > > > > > But, IMO, the position of this section is already misleading: > > > > > >

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Mon, Oct 12, 2015 at 01:54:38PM +0200, Peter Zijlstra wrote: > On Mon, Oct 12, 2015 at 05:06:36PM +0800, Boqun Feng wrote: > > Understood. > > > > But, IMO, the position of this section is already misleading: > > > > (*) Implicit kernel memory barriers. > > - Locking functions. > >

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Mon, Oct 12, 2015 at 05:06:36PM +0800, Boqun Feng wrote: > Understood. > > But, IMO, the position of this section is already misleading: > > (*) Implicit kernel memory barriers. > - Locking functions. > - Interrupt disabling functions. >->- Sleep and wake-up functions.<- >

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Sun, Oct 11, 2015 at 05:40:44PM -0700, Paul E. McKenney wrote: > On Sun, Oct 11, 2015 at 11:26:40PM +0800, Boqun Feng wrote: > > On Tue, Oct 06, 2015 at 06:06:50PM +0200, Peter Zijlstra wrote: > > > On Thu, Sep 24, 2015 at 09:21:22PM +0800, Boqun Feng wrote: > > > > > Included in it are some of

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Sun, Oct 11, 2015 at 05:40:44PM -0700, Paul E. McKenney wrote: > On Sun, Oct 11, 2015 at 11:26:40PM +0800, Boqun Feng wrote: > > On Tue, Oct 06, 2015 at 06:06:50PM +0200, Peter Zijlstra wrote: > > > On Thu, Sep 24, 2015 at 09:21:22PM +0800, Boqun Feng wrote: > > > > > Included in it are some of

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Mon, Oct 12, 2015 at 09:09:24PM +0800, Boqun Feng wrote: > On Mon, Oct 12, 2015 at 01:54:38PM +0200, Peter Zijlstra wrote: > > On Mon, Oct 12, 2015 at 05:06:36PM +0800, Boqun Feng wrote: > > > Understood. > > > > > > But, IMO, the position of this section is already misleading: > > > > > >

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Mon, Oct 12, 2015 at 05:06:36PM +0800, Boqun Feng wrote: > Understood. > > But, IMO, the position of this section is already misleading: > > (*) Implicit kernel memory barriers. > - Locking functions. > - Interrupt disabling functions. >->- Sleep and wake-up functions.<- >

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Mon, Oct 12, 2015 at 01:54:38PM +0200, Peter Zijlstra wrote: > On Mon, Oct 12, 2015 at 05:06:36PM +0800, Boqun Feng wrote: > > Understood. > > > > But, IMO, the position of this section is already misleading: > > > > (*) Implicit kernel memory barriers. > > - Locking functions. > >

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Sun, Oct 11, 2015 at 11:26:40PM +0800, Boqun Feng wrote: > On Tue, Oct 06, 2015 at 06:06:50PM +0200, Peter Zijlstra wrote: > > On Thu, Sep 24, 2015 at 09:21:22PM +0800, Boqun Feng wrote: > > > > Included in it are some of the details on this subject, because a wakeup > > > > has two prior

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Tue, Oct 06, 2015 at 06:06:50PM +0200, Peter Zijlstra wrote: > On Thu, Sep 24, 2015 at 09:21:22PM +0800, Boqun Feng wrote: > > > Included in it are some of the details on this subject, because a wakeup > > > has two prior states that are of importance, the tasks own prior state > > > and the

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Tue, Oct 06, 2015 at 06:06:50PM +0200, Peter Zijlstra wrote: > On Thu, Sep 24, 2015 at 09:21:22PM +0800, Boqun Feng wrote: > > > Included in it are some of the details on this subject, because a wakeup > > > has two prior states that are of importance, the tasks own prior state > > > and the

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Sun, Oct 11, 2015 at 11:26:40PM +0800, Boqun Feng wrote: > On Tue, Oct 06, 2015 at 06:06:50PM +0200, Peter Zijlstra wrote: > > On Thu, Sep 24, 2015 at 09:21:22PM +0800, Boqun Feng wrote: > > > > Included in it are some of the details on this subject, because a wakeup > > > > has two prior

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Wed, Oct 07, 2015 at 01:10:24PM +0200, Peter Zijlstra wrote: > On Tue, Oct 06, 2015 at 06:04:50PM +0200, Peter Zijlstra wrote: > > That said, it would be good if Paul (or anyone really) can explain to me > > the reason for: 5af4692a75da ("smp: Make control dependencies work on > > Alpha,

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Tue, Oct 06, 2015 at 06:04:50PM +0200, Peter Zijlstra wrote: > That said, it would be good if Paul (or anyone really) can explain to me > the reason for: 5af4692a75da ("smp: Make control dependencies work on > Alpha, improve documentation"). The Changelog simply states that Alpha > needs the

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Tue, Oct 06, 2015 at 06:04:50PM +0200, Peter Zijlstra wrote: > That said, it would be good if Paul (or anyone really) can explain to me > the reason for: 5af4692a75da ("smp: Make control dependencies work on > Alpha, improve documentation"). The Changelog simply states that Alpha > needs the

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Wed, Oct 07, 2015 at 01:10:24PM +0200, Peter Zijlstra wrote: > On Tue, Oct 06, 2015 at 06:04:50PM +0200, Peter Zijlstra wrote: > > That said, it would be good if Paul (or anyone really) can explain to me > > the reason for: 5af4692a75da ("smp: Make control dependencies work on > > Alpha,

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

> On Mon, Sep 21, 2015 at 07:46:11PM +0200, Oleg Nesterov wrote: > > In short, I got lost ;) Now I don't even understand why we do not need > > another rmb() between p->on_rq and p->on_cpu. Suppose a thread T does > > > > set_current_state(...); > > schedule(); > > > > it can be

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Tue, Oct 06, 2015 at 06:24:23PM +0200, Peter Zijlstra wrote: > On Tue, Oct 06, 2015 at 06:04:50PM +0200, Peter Zijlstra wrote: > > On Mon, Sep 21, 2015 at 07:46:11PM +0200, Oleg Nesterov wrote: > > > On 09/18, Peter Zijlstra wrote: > > > > > > > > the text is correct, right? > > > > > > Yes,

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Tue, Oct 06, 2015 at 06:04:50PM +0200, Peter Zijlstra wrote: > On Mon, Sep 21, 2015 at 07:46:11PM +0200, Oleg Nesterov wrote: > > On 09/18, Peter Zijlstra wrote: > > > > > > the text is correct, right? > > > > Yes, it looks good to me and helpful. > > > > But damn. I forgot why exactly

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Thu, Sep 24, 2015 at 09:21:22PM +0800, Boqun Feng wrote: > > Included in it are some of the details on this subject, because a wakeup > > has two prior states that are of importance, the tasks own prior state > > and the wakeup state, both should be considered in the 'program order' > > flow. >

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Mon, Sep 21, 2015 at 07:46:11PM +0200, Oleg Nesterov wrote: > On 09/18, Peter Zijlstra wrote: > > > > the text is correct, right? > > Yes, it looks good to me and helpful. > > But damn. I forgot why exactly try_to_wake_up() needs rmb() after > ->on_cpu check... It looks reasonable in any

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

> On Mon, Sep 21, 2015 at 07:46:11PM +0200, Oleg Nesterov wrote: > > In short, I got lost ;) Now I don't even understand why we do not need > > another rmb() between p->on_rq and p->on_cpu. Suppose a thread T does > > > > set_current_state(...); > > schedule(); > > > > it can be

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Tue, Oct 06, 2015 at 06:24:23PM +0200, Peter Zijlstra wrote: > On Tue, Oct 06, 2015 at 06:04:50PM +0200, Peter Zijlstra wrote: > > On Mon, Sep 21, 2015 at 07:46:11PM +0200, Oleg Nesterov wrote: > > > On 09/18, Peter Zijlstra wrote: > > > > > > > > the text is correct, right? > > > > > > Yes,

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Thu, Sep 24, 2015 at 09:21:22PM +0800, Boqun Feng wrote: > > Included in it are some of the details on this subject, because a wakeup > > has two prior states that are of importance, the tasks own prior state > > and the wakeup state, both should be considered in the 'program order' > > flow. >

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Mon, Sep 21, 2015 at 07:46:11PM +0200, Oleg Nesterov wrote: > On 09/18, Peter Zijlstra wrote: > > > > the text is correct, right? > > Yes, it looks good to me and helpful. > > But damn. I forgot why exactly try_to_wake_up() needs rmb() after > ->on_cpu check... It looks reasonable in any

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Tue, Oct 06, 2015 at 06:04:50PM +0200, Peter Zijlstra wrote: > On Mon, Sep 21, 2015 at 07:46:11PM +0200, Oleg Nesterov wrote: > > On 09/18, Peter Zijlstra wrote: > > > > > > the text is correct, right? > > > > Yes, it looks good to me and helpful. > > > > But damn. I forgot why exactly

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

Hi Peter, On Thu, Sep 17, 2015 at 03:01:26PM +0200, Peter Zijlstra wrote: > On Thu, Sep 10, 2015 at 07:55:57PM +0200, Oleg Nesterov wrote: > > On 09/10, Boqun Feng wrote: > > > > > > On Wed, Sep 09, 2015 at 12:28:22PM -0700, Paul E. McKenney wrote: > > > > My feeling is > > > > that we should

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

Hi Peter, On Thu, Sep 17, 2015 at 03:01:26PM +0200, Peter Zijlstra wrote: > On Thu, Sep 10, 2015 at 07:55:57PM +0200, Oleg Nesterov wrote: > > On 09/10, Boqun Feng wrote: > > > > > > On Wed, Sep 09, 2015 at 12:28:22PM -0700, Paul E. McKenney wrote: > > > > My feeling is > > > > that we should

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On 09/18, Peter Zijlstra wrote: > > the text is correct, right? Yes, it looks good to me and helpful. But damn. I forgot why exactly try_to_wake_up() needs rmb() after ->on_cpu check... It looks reasonable in any case, but I do not see any strong reason immediately. Say,

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On 09/18, Peter Zijlstra wrote: > > the text is correct, right? Yes, it looks good to me and helpful. But damn. I forgot why exactly try_to_wake_up() needs rmb() after ->on_cpu check... It looks reasonable in any case, but I do not see any strong reason immediately. Say,

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Thu, Sep 17, 2015 at 07:01:11PM +0200, Oleg Nesterov wrote: > On 09/17, Peter Zijlstra wrote: > > > > Included in it are some of the details on this subject, because a wakeup > > has two prior states that are of importance, the tasks own prior state > > and the wakeup state, both should be

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Thu, Sep 17, 2015 at 07:01:11PM +0200, Oleg Nesterov wrote: > On 09/17, Peter Zijlstra wrote: > > > > Included in it are some of the details on this subject, because a wakeup > > has two prior states that are of importance, the tasks own prior state > > and the wakeup state, both should be

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On 09/17, Peter Zijlstra wrote: > > Included in it are some of the details on this subject, because a wakeup > has two prior states that are of importance, the tasks own prior state > and the wakeup state, both should be considered in the 'program order' > flow. Great. Just one question, > + *

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Thu, Sep 10, 2015 at 07:55:57PM +0200, Oleg Nesterov wrote: > On 09/10, Boqun Feng wrote: > > > > On Wed, Sep 09, 2015 at 12:28:22PM -0700, Paul E. McKenney wrote: > > > My feeling is > > > that we should avoid saying too much about the internals of wait_event() > > > and wake_up(). > > I feel

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Thu, Sep 10, 2015 at 07:55:57PM +0200, Oleg Nesterov wrote: > On 09/10, Boqun Feng wrote: > > > > On Wed, Sep 09, 2015 at 12:28:22PM -0700, Paul E. McKenney wrote: > > > My feeling is > > > that we should avoid saying too much about the internals of wait_event() > > > and wake_up(). > > I feel

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On 09/17, Peter Zijlstra wrote: > > Included in it are some of the details on this subject, because a wakeup > has two prior states that are of importance, the tasks own prior state > and the wakeup state, both should be considered in the 'program order' > flow. Great. Just one question, > + *

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

Hi Oleg, On Thu, Sep 10, 2015 at 07:55:57PM +0200, Oleg Nesterov wrote: > On 09/10, Boqun Feng wrote: > > > > On Wed, Sep 09, 2015 at 12:28:22PM -0700, Paul E. McKenney wrote: > > > My feeling is > > > that we should avoid saying too much about the internals of wait_event() > > > and wake_up(). >

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

Hi Oleg, On Thu, Sep 10, 2015 at 07:55:57PM +0200, Oleg Nesterov wrote: > On 09/10, Boqun Feng wrote: > > > > On Wed, Sep 09, 2015 at 12:28:22PM -0700, Paul E. McKenney wrote: > > > My feeling is > > > that we should avoid saying too much about the internals of wait_event() > > > and wake_up(). >

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On 09/10, Boqun Feng wrote: > > On Wed, Sep 09, 2015 at 12:28:22PM -0700, Paul E. McKenney wrote: > > My feeling is > > that we should avoid saying too much about the internals of wait_event() > > and wake_up(). I feel the same. I simply can't understand what we are trying to document ;) For

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On 09/10, Boqun Feng wrote: > > On Wed, Sep 09, 2015 at 12:28:22PM -0700, Paul E. McKenney wrote: > > My feeling is > > that we should avoid saying too much about the internals of wait_event() > > and wake_up(). I feel the same. I simply can't understand what we are trying to document ;) For

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Wed, Sep 09, 2015 at 12:28:22PM -0700, Paul E. McKenney wrote: > On Tue, Sep 08, 2015 at 09:14:01AM +0800, Boqun Feng wrote: > > Two examples for barriers in wake_up() and co. in memory-barriers.txt > > are misleading, along with their explanations: > > > > 1. The example which wanted to

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Tue, Sep 08, 2015 at 09:14:01AM +0800, Boqun Feng wrote: > Two examples for barriers in wake_up() and co. in memory-barriers.txt > are misleading, along with their explanations: > > 1.The example which wanted to explain the write barrier in > wake_up() and co. [spotted by Oleg

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Wed, Sep 09, 2015 at 12:28:22PM -0700, Paul E. McKenney wrote: > On Tue, Sep 08, 2015 at 09:14:01AM +0800, Boqun Feng wrote: > > Two examples for barriers in wake_up() and co. in memory-barriers.txt > > are misleading, along with their explanations: > > > > 1. The example which wanted to

Re: [PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

On Tue, Sep 08, 2015 at 09:14:01AM +0800, Boqun Feng wrote: > Two examples for barriers in wake_up() and co. in memory-barriers.txt > are misleading, along with their explanations: > > 1.The example which wanted to explain the write barrier in > wake_up() and co. [spotted by Oleg

[PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

Two examples for barriers in wake_up() and co. in memory-barriers.txt are misleading, along with their explanations: 1. The example which wanted to explain the write barrier in wake_up() and co. [spotted by Oleg Nesterov ] 2. The example which wanted to explain that the write

[PATCH] Documentation: Remove misleading examples of the barriers in wake_*()

Two examples for barriers in wake_up() and co. in memory-barriers.txt are misleading, along with their explanations: 1. The example which wanted to explain the write barrier in wake_up() and co. [spotted by Oleg Nesterov ] 2. The example which wanted to explain