linux-kernel - Re: [PATCH 1/11] Add generic helpers for arch IPI function calls

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]

Message-ID: <480DACDD.7040108@qumranet.com>
Date:	Tue, 22 Apr 2008 12:16:13 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	Jens Axboe <jens.axboe@...cle.com>
CC:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	npiggin@...e.de, torvalds@...ux-foundation.org
Subject: Re: [PATCH 1/11] Add generic helpers for arch IPI function calls

Jens Axboe wrote:
> This adds kernel/smp.c which contains helpers for IPI function calls. In
> addition to supporting the existing smp_call_function() in a more efficient
> manner, it also adds a more scalable variant called smp_call_function_single()
> for calling a given function on a single CPU only.
>
> The core of this is based on the x86-64 patch from Nick Piggin, lots of
> changes since then. "Alan D. Brunelle" <Alan.Brunelle@...com> has
> contributed lots of fixes and suggestions as well.
>
> +int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
> +			     int retry, int wait)
> +{
> +	unsigned long flags;
> +	/* prevent preemption and reschedule on another processor */
> +	int me = get_cpu();
> +	int ret = 0;
> +
> +	/* Can deadlock when called with interrupts disabled */
> +	WARN_ON(wait && irqs_disabled());
> +
> +	if (cpu == me) {
> +		local_irq_save(flags);
> +		func(info);
> +		local_irq_restore(flags);
> +	} else {
> +		struct call_single_data d;
> +		struct call_single_data *data;
> +
> +		if (!wait) {
> +			data = kmalloc(sizeof(*data), GFP_ATOMIC);
> +			if (unlikely(!data)) {
> +				ret = -ENOMEM;
> +				goto out;
> +			}
> +			data->flags = CSD_FLAG_ALLOC;
> +		} else {
> +			data = &d;
> +			data->flags = CSD_FLAG_WAIT;
> +		}
> +
>   

Instead of introducing a rare error case, how about falling back to the 
wait case if the allocation fails?

Of course, if the called function relies on the calling cpu doing 
something else, then this fails, but I don't think anybody would do 
that?  On the other hand, there is at least one use of 
smp_call_function_single() with !wait, which doesn't check the error return.

-- 
error compiling committee.c: too many arguments to function

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/