From: Petr Mladek <pmladek@suse.com>
To: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Luis Chamberlain <mcgrof@kernel.org>,
david@redhat.com, patches@lists.linux.dev,
linux-modules@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, petr.pavlu@suse.com,
prarit@redhat.com, gregkh@linuxfoundation.org, rafael@kernel.org,
christophe.leroy@csgroup.eu, tglx@linutronix.de, song@kernel.org,
rppt@kernel.org, willy@infradead.org, vbabka@suse.cz,
mhocko@suse.com, dave.hansen@linux.intel.com
Subject: Re: [PATCH 4/7] sempahore: add a helper for a concurrency limiter
Date: Fri, 31 Mar 2023 10:05:48 +0200 [thread overview]
Message-ID: <ZCaUXHxYiPolI/lu@alley> (raw)
In-Reply-To: <20230331034209.GA12892@google.com>
On Fri 2023-03-31 12:42:09, Sergey Senozhatsky wrote:
> On (23/03/30 09:23), Linus Torvalds wrote:
> > Although we also do have some other issues - I think down_trylock() is
> > ok in irq contexts, but mutex_trylock() is not. Maybe that's why
> > printk uses semaphores? I forget.
>
> Yes, correct. IIRC we also cannot safely call mutex_unlock() from IRQ
> context because it takes some internal mutex spin_lock in a non-IRQ-safe
> manner. Semaphore is OK in this regard, both semaphore try_lock() and
> unlock() can be called from IRQ.
One more reason is that mutex must be released in the same context
that took it. And printk() tries to pass console_sem() to another context.
It was added by the commit dbdda842fe96 ("printk: Add console owner
and waiter logic to load balance console writes"). It was relatively
effective in reducing the risk of soft lockups.
Best Regards,
Petr
next prev parent reply other threads:[~2023-03-31 8:05 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-29 5:31 [PATCH 0/7] module: avoid userspace pressure on unwanted allocations Luis Chamberlain
2023-03-29 5:31 ` [PATCH 1/7] module: move finished_loading() Luis Chamberlain
2023-03-29 5:31 ` [PATCH 2/7] module: extract patient module check into helper Luis Chamberlain
2023-03-29 5:31 ` [PATCH 3/7] module: avoid allocation if module is already present and ready Luis Chamberlain
2023-03-29 5:31 ` [PATCH 4/7] sempahore: add a helper for a concurrency limiter Luis Chamberlain
2023-03-29 7:21 ` Peter Zijlstra
2023-03-29 7:51 ` Luis Chamberlain
2023-03-29 9:19 ` Peter Zijlstra
2023-03-29 9:49 ` Luis Chamberlain
2023-03-29 10:14 ` Peter Zijlstra
2023-03-29 16:50 ` Linus Torvalds
2023-03-30 11:56 ` Peter Zijlstra
2023-03-30 16:23 ` Linus Torvalds
2023-03-31 3:42 ` Sergey Senozhatsky
2023-03-31 8:05 ` Petr Mladek [this message]
2023-03-31 3:45 ` Luis Chamberlain
2023-03-31 4:06 ` Matthew Wilcox
2023-03-31 4:13 ` Luis Chamberlain
2023-03-31 4:11 ` Sergey Senozhatsky
2023-03-29 5:31 ` [PATCH 5/7] modules/kmod: replace implementation with a sempahore Luis Chamberlain
2023-03-29 5:31 ` [PATCH 6/7] debugfs: add debugfs_create_atomic64_t for atomic64_t Luis Chamberlain
2023-03-29 5:46 ` Greg KH
2023-03-29 5:31 ` [PATCH 7/7] module: add debug stats to help identify memory pressure Luis Chamberlain
2023-03-29 5:46 ` Greg KH
2023-03-29 6:04 ` Luis Chamberlain
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=ZCaUXHxYiPolI/lu@alley \
--to=pmladek@suse.com \
--cc=christophe.leroy@csgroup.eu \
--cc=dave.hansen@linux.intel.com \
--cc=david@redhat.com \
--cc=gregkh@linuxfoundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-modules@vger.kernel.org \
--cc=mcgrof@kernel.org \
--cc=mhocko@suse.com \
--cc=patches@lists.linux.dev \
--cc=peterz@infradead.org \
--cc=petr.pavlu@suse.com \
--cc=prarit@redhat.com \
--cc=rafael@kernel.org \
--cc=rppt@kernel.org \
--cc=senozhatsky@chromium.org \
--cc=song@kernel.org \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
--cc=vbabka@suse.cz \
--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