From: Julien Thierry <julien.thierry@arm.com>
To: Valentin Schneider <valentin.schneider@arm.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Cc: peterz@infradead.org, catalin.marinas@arm.com,
will.deacon@arm.com, mingo@redhat.com, james.morse@arm.com,
hpa@zytor.com
Subject: Re: [PATCH v3 3/4] uaccess: Check no rescheduling function is called in unsafe region
Date: Mon, 4 Feb 2019 13:27:17 +0000 [thread overview]
Message-ID: <f2e6ea55-40fa-6d4d-3262-6f6b3791c9d4@arm.com> (raw)
In-Reply-To: <9ba3c7a7-80a8-da29-ffb7-3841ea8548b5@arm.com>
On 30/01/2019 16:58, Valentin Schneider wrote:
> On 15/01/2019 13:58, Julien Thierry wrote:
> [...]> @@ -6151,6 +6159,20 @@ void ___might_sleep(const char *file, int line, int preempt_offset)
>> EXPORT_SYMBOL(___might_sleep);
>> #endif
>>
>> +#ifdef CONFIG_DEBUG_UACCESS_SLEEP
>> +void __might_resched(const char *file, int line)
>> +{
>> + if (!unsafe_user_region_active())
>> + return;
>> +
>> + printk(KERN_ERR
>> + "BUG: rescheduling function called from user access context at %s:%d\n",
>> + file, line);
>> + dump_stack();
>
> Since I've been staring intensely at ___might_sleep() lately, I was thinking
> we could "copy" it a bit more closely (sorry for going back on what I said
> earlier).
>
> Coming back to the double warnings (__might_resched() + schedule_debug()),
> it might be better to drop the schedule_debug() warning and just have the
> one in __might_resched() - if something goes wrong, there'll already be a
> "BUG" in the log.
>
My only worry with that approach is that if someone has a function that
does resched but does not include the annotation __might_resched() we'd
miss the fact that something went wrong.
But that might be a lot of "if"s since that assumes that something does
go wrong.
Could I have a maintainers opinion on this to know if I respin it?
>> +}
>> +EXPORT_SYMBOL(__might_resched);
>> +#endif
>> +
>> #ifdef CONFIG_MAGIC_SYSRQ
>> void normalize_rt_tasks(void)
>> {
>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>> index d4df5b2..d030e31 100644
>> --- a/lib/Kconfig.debug
>> +++ b/lib/Kconfig.debug
>> @@ -2069,6 +2069,14 @@ config IO_STRICT_DEVMEM
>>
>> If in doubt, say Y.
>>
>> +config DEBUG_UACCESS_SLEEP
>> + bool "Check sleep inside a user access region"
>> + depends on DEBUG_KERNEL
>> + help
>> + If you say Y here, various routines which may sleep will become very
>> + noisy if they are called inside a user access region (i.e. between
>> + a user_access_begin() and a user_access_end())
>
> If it does get noisy, we should go for some ratelimiting - it's probably
> good practice even if it is not noisy actually.
>
> ___might_sleep() has this:
>
> if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
> return;
> prev_jiffy = jiffies;
>
I guess the noisiness could depend on the arch specific handling of user
accesses. So yes I guess it might be a good idea to add this.
Thanks,
--
Julien Thierry
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next prev parent reply other threads:[~2019-02-04 13:27 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-15 13:58 [PATCH v3 0/4] uaccess: Add unsafe accessors for arm64 Julien Thierry
2019-01-15 13:58 ` [PATCH v3 1/4] arm64: uaccess: Cleanup get/put_user() Julien Thierry
2019-01-15 13:58 ` [PATCH v3 2/4] arm64: uaccess: Implement unsafe accessors Julien Thierry
2019-01-15 13:58 ` [PATCH v3 3/4] uaccess: Check no rescheduling function is called in unsafe region Julien Thierry
2019-01-30 16:58 ` Valentin Schneider
2019-02-04 13:27 ` Julien Thierry [this message]
2019-02-11 13:45 ` Ingo Molnar
2019-02-11 13:51 ` Peter Zijlstra
2019-02-12 9:15 ` Julien Thierry
2019-02-13 8:21 ` Ingo Molnar
2019-02-13 10:35 ` Peter Zijlstra
2019-02-13 10:50 ` Julien Thierry
2019-02-13 13:17 ` Peter Zijlstra
2019-02-13 13:20 ` Peter Zijlstra
2019-02-13 14:00 ` Will Deacon
2019-02-13 14:07 ` Julien Thierry
2019-02-13 14:17 ` Peter Zijlstra
2019-02-13 14:24 ` Julien Thierry
2019-02-13 14:40 ` Peter Zijlstra
2019-02-13 15:08 ` Peter Zijlstra
2019-02-13 14:25 ` Peter Zijlstra
2019-02-13 14:39 ` Julien Thierry
2019-02-13 14:41 ` Peter Zijlstra
2019-02-13 15:45 ` Peter Zijlstra
2019-02-13 18:54 ` Peter Zijlstra
[not found] ` <D61C430D-4321-4114-AB85-671A3C7B8EAE@amacapital.net>
2019-02-13 22:21 ` Peter Zijlstra
2019-02-13 22:49 ` Andy Lutomirski
2019-02-14 10:14 ` [PATCH] sched/x86: Save [ER]FLAGS on context switch Peter Zijlstra
2019-02-14 16:18 ` Brian Gerst
2019-02-14 19:34 ` Peter Zijlstra
2019-02-15 14:34 ` Brian Gerst
2019-02-15 17:18 ` Linus Torvalds
2019-02-15 17:40 ` Peter Zijlstra
2019-02-15 18:28 ` Andy Lutomirski
2019-02-15 23:34 ` Peter Zijlstra
2019-02-16 0:21 ` Linus Torvalds
2019-02-16 10:32 ` Peter Zijlstra
2019-02-16 4:06 ` hpa
2019-02-16 10:30 ` Peter Zijlstra
2019-02-18 22:30 ` H. Peter Anvin
2019-02-19 0:24 ` Linus Torvalds
2019-02-19 2:20 ` Andy Lutomirski
2019-02-19 2:46 ` H. Peter Anvin
2019-02-19 9:07 ` Julien Thierry
2019-02-19 8:53 ` Julien Thierry
2019-02-19 9:15 ` Peter Zijlstra
2019-02-19 9:19 ` Peter Zijlstra
2019-02-19 9:04 ` Peter Zijlstra
2019-02-19 9:21 ` hpa
2019-02-19 9:44 ` Peter Zijlstra
2019-02-19 11:38 ` Thomas Gleixner
2019-02-19 11:58 ` Peter Zijlstra
2019-02-19 12:48 ` Will Deacon
2019-02-20 22:55 ` H. Peter Anvin
2019-02-21 12:06 ` Julien Thierry
2019-02-21 21:35 ` Thomas Gleixner
2019-02-21 22:08 ` Linus Torvalds
2019-02-22 12:58 ` Peter Zijlstra
2019-02-22 18:10 ` Thomas Gleixner
2019-02-22 22:26 ` [RFC][PATCH] objtool: STAC/CLAC validation Peter Zijlstra
2019-02-22 23:34 ` Linus Torvalds
2019-02-23 8:43 ` Peter Zijlstra
2019-02-22 23:39 ` hpa
2019-02-23 8:39 ` Peter Zijlstra
2019-02-25 8:47 ` hpa
2019-02-25 13:21 ` Peter Zijlstra
2019-03-01 15:07 ` Peter Zijlstra
2019-02-25 8:49 ` hpa
2019-02-22 23:55 ` Andy Lutomirski
2019-02-23 8:37 ` Peter Zijlstra
2019-02-23 10:52 ` Peter Zijlstra
2019-02-25 10:51 ` Peter Zijlstra
2019-02-25 11:53 ` Peter Zijlstra
2019-02-25 15:36 ` Andy Lutomirski
2019-02-23 0:34 ` Andy Lutomirski
2019-02-23 1:12 ` Linus Torvalds
2019-02-23 1:16 ` Andy Lutomirski
2019-02-23 1:33 ` Linus Torvalds
2019-02-23 1:40 ` Linus Torvalds
2019-02-25 8:33 ` Julien Thierry
2019-02-25 11:55 ` Peter Zijlstra
2019-02-21 12:46 ` [PATCH] sched/x86: Save [ER]FLAGS on context switch Will Deacon
2019-02-21 22:06 ` Andy Lutomirski
2019-02-18 9:03 ` [PATCH v2] " Peter Zijlstra
2019-02-13 23:19 ` [PATCH v3 3/4] uaccess: Check no rescheduling function is called in unsafe region Linus Torvalds
2019-01-15 13:58 ` [PATCH v3 4/4] arm64: uaccess: Implement user_access_region_active Julien Thierry
2019-01-25 14:27 ` [PATCH v3 0/4] uaccess: Add unsafe accessors for arm64 Catalin Marinas
2019-01-30 16:17 ` Julien Thierry
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