From: Alexnader Kuleshov <kuleshovmail@gmail.com>
To: open list <linux-kernel@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Andy Lutomirski <luto@kernel.org>,
Paul Gortmaker <paul.gortmaker@windriver.com>,
Jan Beulich <jbeulich@suse.com>, Tony Luck <tony.luck@intel.com>,
Jianyu Zhan <nasa4836@gmail.com>
Subject: Question: goal of twice disabling of preemption in exception handlers
Date: Sun, 20 Nov 2016 23:52:07 +0600 [thread overview]
Message-ID: <20161120175207.GA4354@localhost> (raw)
Hello everyone,
Exception handlers which may run on IST stack disable and enable preemption
twice. For example do_int3() [1]. This one calls ist_enter() which
disables preemption with preempt_disable() every time without any conditions.
And later do_int3() calls preempt_disable() again [2] before do_trap().
Of course we decrement preemption counter in the end of such exception
handlers twice too. But what's actual purpose of doing this two times?
[1] https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/arch/x86/kernel/traps.c?id=refs/tags/next-20161117#n530
[2] https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/arch/x86/kernel/traps.c?id=refs/tags/next-20161117#n566
Thank you.
next reply other threads:[~2016-11-20 17:52 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-20 17:52 Alexnader Kuleshov [this message]
2016-11-27 18:57 ` Question: goal of twice disabling of preemption in exception handlers Andy Lutomirski
2016-11-27 19:45 ` Alexnader Kuleshov
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=20161120175207.GA4354@localhost \
--to=kuleshovmail@gmail.com \
--cc=bp@alien8.de \
--cc=jbeulich@suse.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=nasa4836@gmail.com \
--cc=paul.gortmaker@windriver.com \
--cc=tglx@linutronix.de \
--cc=tony.luck@intel.com \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.