From: Byungchul Park <byungchul.park@lge.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@kernel.org, tglx@linutronix.de, walken@google.com,
boqun.feng@gmail.com, kirill@shutemov.name,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
akpm@linux-foundation.org, willy@infradead.org,
npiggin@gmail.com, kernel-team@lge.com
Subject: Re: [PATCH v7 06/16] lockdep: Detect and handle hist_lock ring buffer overwrite
Date: Thu, 13 Jul 2017 11:07:45 +0900 [thread overview]
Message-ID: <20170713020745.GG20323@X58A-UD3R> (raw)
In-Reply-To: <20170712075617.o2jds2giuoqxjqic@hirez.programming.kicks-ass.net>
On Wed, Jul 12, 2017 at 09:56:17AM +0200, Peter Zijlstra wrote:
> On Wed, Jul 12, 2017 at 11:00:53AM +0900, Byungchul Park wrote:
> > On Tue, Jul 11, 2017 at 06:12:32PM +0200, Peter Zijlstra wrote:
>
> > > Right, like I wrote in the comment; I don't think you need quite this
> > > much.
> > >
> > > The problem only happens if you rewind more than MAX_XHLOCKS_NR;
> > > although I realize it can be an accumulative rewind, which makes it
> > > slightly more tricky.
> > >
> > > We can either make the rewind more expensive and make xhlock_valid()
> > > false for each rewound entry; or we can keep the max_idx and account
> >
> > Does max_idx mean the 'original position - 1'?
>
> orig_idx = current->hist_idx;
> current->hist_idx++;
> if ((int)(current->hist_idx - orig_idx) > 0)
> current->hist_idx_max = current->hist_idx;
>
>
> I've forgotten if the idx points to the most recent entry or beyond it.
>
> Given the circular nature, and tail being one ahead of head, the max
> effectively tracks the tail (I suppose we can also do an explicit tail
> tracking, but that might end up more difficult).
>
> This allows rewinds of less than array_size() while still maintaining a
> correct tail.
>
> Only once we (cummulative or not) rewind past the tail -- iow, loose the
> _entire_ history, do we need to do something drastic.
I am sorry but I don't understand why we have to do the drastic work.
Does my approach have problems, rewinding to 'original idx' on exit and
deciding whether overwrite or not? I think, this way, no need to do the
drastic work. Or.. does my one get more overhead in usual case?
>
> > > from there. If we rewind >= MAX_XHLOCKS_NR from the max_idx we need to
> > > invalidate the entire state, which we can do by invaliding
> >
> > Could you explain what the entire state is?
>
> All hist_lock[]. Did the above help?
>
> > > xhlock_valid() or by re-introduction of the hist_gen_id. When we
> >
> > What does the re-introduction of the hist_gen_id mean?
>
> What you used to call work_id or something like that. A generation count
> for the hist_lock[].
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-07-13 2:08 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-24 8:59 [PATCH v7 00/16] lockdep: Implement crossrelease feature Byungchul Park
2017-05-24 8:59 ` [PATCH v7 01/16] lockdep: Refactor lookup_chain_cache() Byungchul Park
2017-05-24 8:59 ` [PATCH v7 02/16] lockdep: Add a function building a chain between two classes Byungchul Park
2017-05-24 8:59 ` [PATCH v7 03/16] lockdep: Change the meaning of check_prev_add()'s return value Byungchul Park
2017-05-24 8:59 ` [PATCH v7 04/16] lockdep: Make check_prev_add() able to handle external stack_trace Byungchul Park
2017-05-24 8:59 ` [PATCH v7 05/16] lockdep: Implement crossrelease feature Byungchul Park
2017-06-13 0:33 ` Byungchul Park
2017-06-22 23:27 ` Byungchul Park
2017-07-11 16:04 ` Peter Zijlstra
2017-07-12 2:24 ` Byungchul Park
2017-05-24 8:59 ` [PATCH v7 06/16] lockdep: Detect and handle hist_lock ring buffer overwrite Byungchul Park
2017-07-11 16:12 ` Peter Zijlstra
2017-07-12 2:00 ` Byungchul Park
2017-07-12 7:56 ` Peter Zijlstra
2017-07-13 2:07 ` Byungchul Park [this message]
2017-07-13 8:14 ` Peter Zijlstra
2017-07-13 8:57 ` Byungchul Park
2017-07-13 9:50 ` Peter Zijlstra
2017-07-13 10:09 ` Byungchul Park
2017-07-13 10:29 ` Peter Zijlstra
2017-07-13 11:12 ` Peter Zijlstra
2017-07-13 11:23 ` Byungchul Park
2017-07-14 1:41 ` Byungchul Park
2017-07-14 6:42 ` Byungchul Park
2017-07-21 13:54 ` Peter Zijlstra
2017-07-25 6:29 ` Byungchul Park
2017-07-25 8:45 ` Peter Zijlstra
2017-07-13 11:19 ` Byungchul Park
2017-07-18 1:25 ` Byungchul Park
2017-05-24 8:59 ` [PATCH v7 07/16] lockdep: Handle non(or multi)-acquisition of a crosslock Byungchul Park
2017-05-24 8:59 ` [PATCH v7 08/16] lockdep: Avoid adding redundant direct links of crosslocks Byungchul Park
2017-07-25 15:41 ` Peter Zijlstra
2017-07-26 7:16 ` Byungchul Park
2017-05-24 8:59 ` [PATCH v7 09/16] lockdep: Fix incorrect condition to print bug msgs for MAX_LOCKDEP_CHAIN_HLOCKS Byungchul Park
2017-05-24 8:59 ` [PATCH v7 10/16] lockdep: Make print_circular_bug() aware of crossrelease Byungchul Park
2017-05-24 8:59 ` [PATCH v7 11/16] lockdep: Apply crossrelease to completions Byungchul Park
2017-05-24 8:59 ` [PATCH v7 12/16] pagemap.h: Remove trailing white space Byungchul Park
2017-05-24 8:59 ` [PATCH v7 13/16] lockdep: Apply crossrelease to PG_locked locks Byungchul Park
2017-05-24 8:59 ` [PATCH v7 14/16] lockdep: Apply lock_acquire(release) on __Set(__Clear)PageLocked Byungchul Park
2017-05-24 8:59 ` [PATCH v7 15/16] lockdep: Move data of CONFIG_LOCKDEP_PAGELOCK from page to page_ext Byungchul Park
2017-05-24 8:59 ` [PATCH v7 16/16] lockdep: Crossrelease feature documentation Byungchul Park
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170713020745.GG20323@X58A-UD3R \
--to=byungchul.park@lge.com \
--cc=akpm@linux-foundation.org \
--cc=boqun.feng@gmail.com \
--cc=kernel-team@lge.com \
--cc=kirill@shutemov.name \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mingo@kernel.org \
--cc=npiggin@gmail.com \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=walken@google.com \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).