From: Alan Stern <stern@rowland.harvard.edu>
To: Andrea Vai <andrea.vai@unipv.it>
Cc: Greg KH <gregkh@linuxfoundation.org>, <linux-usb@vger.kernel.org>
Subject: Re: Slow I/O on USB media
Date: Wed, 5 Jun 2019 12:11:54 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1906051206350.1788-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <4f2e5b456eb0f53b8c921465c1b1c4813b918f65.camel@unipv.it>
On Wed, 5 Jun 2019, Andrea Vai wrote:
> Hi,
> Il giorno mer, 05/06/2019 alle 10.26 -0400, Alan Stern ha scritto:
> > On Wed, 5 Jun 2019, Andrea Vai wrote:
> >
> > > Hi,
> > > Il giorno mar, 04/06/2019 alle 07.43 +0200, Greg KH ha scritto:
> > > > On Mon, Jun 03, 2019 at 01:13:48PM +0200, Andrea Vai wrote:
> > > > > Il giorno gio, 30/05/2019 alle 06.25 -0700, Greg KH ha
> > scritto:
> > > > > > [...]
> > > > > Hi,
> > > > >
> > > > > > Any chance you can use 'git bisect' to find the offending
> > > > commit?
> > > > > Yes, I am doing it as I managed to build the kernel from
> > source
> > > >
> > > > Great! What did you find?
> > >
> > > # first bad commit: [534903d60376b4989b76ec445630aa10f2bc3043]
> > > drm/atomic: Use explicit old crtc state in
> > > drm_atomic_add_affected_planes()
> > >
> > > By the way, as I am not expert, is there a way to double-check
> > that I
> > > bisected correctly? (such as, e.g., test with the version before
> > this
> > > one, and then with this commit applied?)
> >
> > That is exactly the way to do it: Build a kernel from that commit
> > and
> > see that it fails, then revert the commit and see that the
> > resulting
> > kernel succeeds.
> >
> > (Note: The notion of "version before" doesn't have a firm meaning
> > in
> > the kernel, because some commits have multiple parents. The best
> > way
> > to see if a single commit caused a change is to do what I said
> > above:
> > revert the commit and see what happens.)
> ok, thank you for pointing it out. So, my question is: how to revert a
> commit? (sorry, I prefer to ask you because I am afraid I could do
> something wrong, and don't trust too much myself and what I pick up
> searching on the web. In the special case, I found "git revert", but
> for example how could I revert back a "reversion"? :-/ (I know I miss
> the basis, I never worked with git, so sorry for the stupid
> question)).
In this case it's very simple, since the 534903d60376 commit does have
a single parent. You can just do "git checkout 534903d60376^".
More generally, you could do "git show 534903d60376 | git apply -R -".
That would tell git to write out the commit in the form of a patch and
then apply the patch in reverse.
Alan Stern
> > Incidentally, it seems very unlikely that a commit for the drm
> > subsystem would have any effect on the behavior of a USB storage
> > device.
>
> well, I had the same doubt and that's the reason I was trying to do
> the check: I'm afraid I have done something wrong or made a mess with
> the bisect process.
>
> Thank you,
> Andrea
next prev parent reply other threads:[~2019-06-05 16:11 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-30 13:18 Slow I/O on USB media Andrea Vai
2019-05-30 13:25 ` Greg KH
2019-06-03 11:13 ` Andrea Vai
2019-06-04 5:43 ` Greg KH
2019-06-04 7:26 ` Andrea Vai
2019-06-05 7:36 ` Andrea Vai
2019-06-05 14:26 ` Alan Stern
2019-06-05 15:46 ` Andrea Vai
2019-06-05 16:11 ` Alan Stern [this message]
2019-06-05 14:55 ` Greg KH
[not found] ` <0c2adde7154b0a6c8b2ad7fc5258916731b78775.camel@unipv.it>
2019-06-05 16:23 ` Andrea Vai
2019-06-05 17:39 ` Greg KH
2019-06-06 8:41 ` Andrea Vai
2019-06-06 9:03 ` Andrea Vai
2019-06-06 14:00 ` Andrea Vai
2019-06-06 14:30 ` Alan Stern
2019-06-06 14:47 ` Greg KH
2019-06-07 7:59 ` Andrea Vai
2019-06-08 7:43 ` Andrea Vai
2019-06-08 9:29 ` Andrea Vai
2019-06-10 14:38 ` Greg KH
2019-06-11 6:48 ` Andrea Vai
2019-06-10 14:40 ` Alan Stern
2019-06-10 14:55 ` Andrea Vai
2019-06-10 16:20 ` Alan Stern
2019-06-17 15:52 ` Andrea Vai
2019-06-17 16:14 ` Alan Stern
2019-06-17 16:34 ` Andrea Vai
2019-06-17 17:28 ` Alan Stern
2019-07-01 17:52 ` Andrea Vai
2019-07-01 18:57 ` Alan Stern
2019-06-10 14:37 ` Greg KH
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