linux-kernel - Re: [PATCH v4 1/2] mm: refactor __vunmap() to avoid duplicated call to find_vm

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Message-ID: <05c40b0b-3621-6c07-346b-478679949d92@gmail.com>
Date:   Thu, 18 Apr 2019 16:17:59 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>
Cc:     Roman Gushchin <guroan@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-team@...com,
        Johannes Weiner <hannes@...xchg.org>,
        Vlastimil Babka <vbabka@...e.cz>, Roman Gushchin <guro@...com>,
        Christoph Hellwig <hch@....de>,
        Joel Fernandes <joelaf@...gle.com>
Subject: Re: [PATCH v4 1/2] mm: refactor __vunmap() to avoid duplicated call
 to find_vm_area()



On 04/18/2019 03:24 PM, Andrew Morton wrote:

> afaict, vfree() will only do a mutex_trylock() in
> try_purge_vmap_area_lazy().  So does vfree actually sleep in any
> situation?  Whether or not local interrupts are enabled?

We would be in a big trouble if vfree() could potentially sleep...

Random example : __free_fdtable() called from rcu callback.