linux-kernel - Re: [PATCH v4 7/9] liblockdep: Support using LD

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Message-ID: <20130522092453.GH18810@twins.programming.kicks-ass.net>
Date:	Wed, 22 May 2013 11:24:53 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	torvalds@...ux-foundation.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 7/9] liblockdep: Support using LD_PRELOAD

On Wed, May 15, 2013 at 11:15:39PM -0400, Sasha Levin wrote:
> +static struct lock_lookup __locks[LIBLOCKDEP_STATIC_ENTRIES];
> +static int __locks_nr;
> +
> +static inline bool is_static_lock(struct lock_lookup *lock)
> +{
> +	return lock >= __locks && lock < __locks + ARRAY_SIZE(__locks);
> +}
> +
> +static struct lock_lookup *alloc_lock(void)
> +{
> +	if (__init_state != done) {
> +		/*
> +		 * Some programs attempt to initialize and use locks in their
> +		 * allocation path. This means that a call to malloc() would
> +		 * result in locks being initialized and locked.
> +		 *
> +		 * Why is it an issue for us? dlsym() below will try allocating
> +		 * to give us the original function. Since this allocation will
> +		 * result in a locking operations, we have to let pthread deal
> +		 * with it, but we can't! we don't have the pointer to the
> +		 * original API since we're inside dlsym() trying to get it 
> +		 */
> +
> +		int idx = __locks_nr++;
> +		if (idx >= ARRAY_SIZE(__locks)) {
> +			fprintf(stderr,
> +		"LOCKDEP error: insufficient LIBLOCKDEP_STATIC_ENTRIES\n");
> +			exit(EX_UNAVAILABLE);
> +		}
> +		return __locks + idx;
> +	}
> +
> +	return malloc(sizeof(struct lock_lookup));
> +}

Do we still need this with the glibc __pthread_* static initialization?
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