linux-kernel - Re: [PATCH] rcu: tree: correctly handle sparse possible CPUs

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Message-ID: <CAPAsAGzYxfEsc8EMVHr0NFP1x1CjtdHbi_GApfbu18of98mBvw@mail.gmail.com>
Date:	Wed, 18 May 2016 18:15:23 +0300
From:	Andrey Ryabinin <ryabinin.a.a@...il.com>
To:	Mark Rutland <mark.rutland@....com>
Cc:	paulmck@...ux.vnet.ibm.com,
	Catalin Marinas <catalin.marinas@....com>, dennis.chen@....com,
	jiangshanlai@...il.com, josh@...htriplett.org,
	LKML <linux-kernel@...r.kernel.org>,
	mathieu.desnoyers@...icios.com,
	Steven Rostedt <rostedt@...dmis.org>, steve.capper@....com,
	Will Deacon <will.deacon@....com>
Subject: Re: [PATCH] rcu: tree: correctly handle sparse possible CPUs

2016-05-16 19:48 GMT+03:00 Mark Rutland <mark.rutland@....com>:

>  /*
> + * Iterate over all possible CPUs in a leaf RCU node.
> + */
> +#define for_each_leaf_node_possible_cpu(rnp, cpu) \
> +       for ((cpu) = rnp->grplo; \
> +            cpu <= rnp->grphi; \
> +            cpu = cpumask_next((cpu), cpu_possible_mask))
> +
> +/*
> + * Iterate over all possible CPUs in a leaf RCU node, at each step providing a
> + * bit for comparison against rcu_node bitmasks.
> + */
> +#define for_each_leaf_node_possible_cpu_bit(rnp, cpu, bit) \
> +       for ((cpu) = rnp->grplo, (bit) = 1; \
> +            cpu <= rnp->grphi; \
> +            cpu = cpumask_next((cpu), cpu_possible_mask), \
> +                  (bit) = 1UL << (cpu - rnp->grplo))
> +


[    0.163652] UBSAN: Undefined behaviour in ../kernel/rcu/tree.c:2912:3
[    0.164000] shift exponent 64 is too large for 64-bit type 'long
unsigned int'