From: Jeff Johnston <jjohnstn@redhat.com>
To: "Torbjörn SVENSSON" <torbjorn.svensson@foss.st.com>
Cc: Newlib <newlib@sourceware.org>
Subject: Re: [PATCH 1/2] Used chunk needs to be removed from free_list
Date: Thu, 1 Sep 2022 14:41:15 -0400 [thread overview]
Message-ID: <CAOox84tWOzRzUCZxfFQfep3VCY3LEvi8DhMakT+i=A+4oXOCaA@mail.gmail.com> (raw)
In-Reply-To: <20220830135625.2247198-1-torbjorn.svensson@foss.st.com>
Patch applied. Thanks.
-- Jeff J.
On Tue, Aug 30, 2022 at 9:57 AM Torbjörn SVENSSON <
torbjorn.svensson@foss.st.com> wrote:
> When using nano malloc and the remaning heap space is not big enough to
> fullfill the allocation, malloc will attempt to merge the last chunk in
> the free list with a new allocation in order to create a bigger chunk.
> This is successful, but the chunk still remains in the free_list, so
> any later call to malloc can give out the same region without it first
> being freed.
>
> Possible sequence to verify:
>
> void *p1 = malloc(3000);
> void *p2 = malloc(4000);
> void *p3 = malloc(5000);
> void *p4 = malloc(6000);
> void *p5 = malloc(7000);
> free(p2);
> free(p4);
> void *p6 = malloc(35000);
> free(p6);
> void *p7 = malloc(42000);
> void *p8 = malloc(32000);
>
> Without the change, p7 and p8 points to the same address.
> Requirement, after malloc(35000), there is less than 42000 bytes
> available on the heap.
>
> Contributed by STMicroelectronics
>
> Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>
> ---
> newlib/libc/stdlib/nano-mallocr.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/newlib/libc/stdlib/nano-mallocr.c
> b/newlib/libc/stdlib/nano-mallocr.c
> index 99ad60dd0..43eb20e07 100644
> --- a/newlib/libc/stdlib/nano-mallocr.c
> +++ b/newlib/libc/stdlib/nano-mallocr.c
> @@ -336,6 +336,15 @@ void * nano_malloc(RARG malloc_size_t s)
> if (sbrk_aligned(RCALL alloc_size) != (void *)-1)
> {
> p->size += alloc_size;
> +
> + /* Remove chunk from free_list */
> + r = free_list;
> + while (r && p != r->next)
> + {
> + r = r->next;
> + }
> + r->next = NULL;
> +
> r = p;
> }
> else
> --
> 2.25.1
>
>
prev parent reply other threads:[~2022-09-01 18:41 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-30 13:56 Torbjörn SVENSSON
2022-08-30 13:56 ` Torbjörn SVENSSON
2022-08-30 13:56 ` [PATCH 2/2] Don't allocate another header when merging chunks Torbjörn SVENSSON
2022-08-30 13:56 ` Torbjörn SVENSSON
2022-09-01 18:44 ` Jeff Johnston
2022-09-01 19:04 ` Torbjorn SVENSSON
2022-09-01 19:36 ` Jeff Johnston
2022-09-01 19:39 ` Jeff Johnston
2022-09-01 18:41 ` Jeff Johnston [this message]
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