linux-kernel - Re: [PATCH] Clockevents: Always call clockevents_program

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 24 Oct 2017 02:21:26 -0700
From:   Sodagudi Prasad <psodagud@...eaurora.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     mingo@...nel.org, viresh.kumar@...aro.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Clockevents: Always call clockevents_program_event

On 2017-10-24 01:37, Thomas Gleixner wrote:
> On Tue, 24 Oct 2017, Prasad Sodagudi wrote:
> 
>> Currently tick_program_event function is not calling
>> clockevents_program_event when  'expires == KTIME_MAX',
>> it is just updating clockevent state to 
>> CLOCK_EVT_STATE_ONESHOT_STOPPED.
>> clockevents_program_event function updates clockevent
>> device next_event by checking clockevent device state,
>> so always call clockevents_program_event() from tick_program_event.
> 
> No. This is fundmentally wrong. If the clockevent is in oneshot stopped
> mode then you cannot call clockevents_program_event(). There is even a
> warning in that code which will trigger.

<Prasad> Yes. There is warning and I overlooked at that part of the code 
and thought
it would return from the clockevents_program_event function after 
next_event update.
   dev->next_event = expires;

         if (clockevent_state_shutdown(dev))
                 return 0;

Thanks tglx for reviewing patch.

How to clean next next_event from clockevent device in the 
ONESHOT_STOPPED state from tick_program_event()?

Shall I update the next patch set with following condition?  Or Any 
other suggestions to fix this path?

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 4237e07..21104b6 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -317,7 +317,8 @@ int clockevents_program_event(struct 
clock_event_device *dev, ktime_t expires,

         dev->next_event = expires;

-       if (clockevent_state_shutdown(dev))
+       if (clockevent_state_shutdown(dev) ||
+               clockevent_state_oneshot_stopped(dev))
                 return 0;

> 
> Thanks,
> 
> 	tglx

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
Forum,
Linux Foundation Collaborative Project