tests: brk_near_huge: Avoid malloc assertion failure

[la ya]

When I run run_tests.py on my computer, I get the following error:

-------

brk_near_huge (2M: 32): brk_near_huge: malloc.c:2379: sysmalloc: Assertion `(old_top == initial_top (av) && old_size == 0) || ((unsigned long) (old_size) >= MINSIZE && prev_inuse (old_top) && ((unsigned long) old_end & (pagesize - 1)) == 0)' failed.

brk_near_huge (2M: 64): brk_near_huge: malloc.c:2379: sysmalloc: Assertion `(old_top == initial_top (av) && old_size == 0) || ((unsigned long) (old_size) >= MINSIZE && prev_inuse (old_top) && ((unsigned long) old_end & (pagesize - 1)) == 0)' failed.

-------

My uname is "Linux GW-Boat 5.4.0-47-generic #51-Ubuntu SMP Fri Sep 4 19:50:52 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux"

This error only occurs when the QUIET_TEST environment variable is set.

After tracking the heap information, I found that calling malloc for the first time after sbrk(0) would cause the brk0 obtained by sbrk(0) to fail. The following is bt information:

 ► f 0     7ffff7dfb260 malloc

   f 1     7ffff7de3aae fopen64+30

   f 2     7ffff7de3aae fopen64+30

   f 3     5555555568ee read_maps+78

   f 4     555555557204 test_addr_huge+52

Because malloc needs a heap to save malloc_chunk related information, and will apply for a large of virtual memory from the kernel through brk(), so the heap has grown

When executing memset(brk0, 0, newbrk-brk0);, malloc_chunk information will also be erased, so an error will occur when executing PASS();->printf->·····->malloc.The following is bt information:

 ► f 0     7ffff7da418b raise+203

   f 1     7ffff7d83859 abort+299

   f 2     7ffff7df645a

   f 3     7ffff7df8abf sysmalloc+1855

   f 4     7ffff7df9913 _int_malloc+3363

   f 5     7ffff7dfb2d4 malloc+116

   f 6     7ffff7de2e84 _IO_file_doallocate+148

   f 7     7ffff7df3050 _IO_doallocbuf+80

   f 8     7ffff7df20b0 _IO_file_overflow+432

   f 9     7ffff7df0835 _IO_file_xsputn+229

   f 10     7ffff7df0835 _IO_file_xsputn+229

So we should call malloc() explicitly to initialize heap-related information.

The following is my solution for reference, maybe there is a better solution

---

diff --git a/tests/brk_near_huge.c b/tests/brk_near_huge.c

index c9662f4..f323ec8 100644

--- a/tests/brk_near_huge.c

+++ b/tests/brk_near_huge.c

@@ -73,8 +73,13 @@ int main(int argc, char *argv[])

        int fd;

        void *brk0, *hugemap_addr, *newbrk;

        char *p;

+       void *tmp;

        int err;

 

+       /*Let malloc be initialized explicitly*/

+       tmp = malloc(32);

+       free(tmp);

+

        test_init(argc, argv);

 

        hpage_size = check_hugepagesize();

[Sandipan Das]

Hi,

I have come across this problem as well and have a slightly
different solution.

https://groups.google.com/forum/#!topic/libhugetlbfs/WCSvOt8UESg

Please have a look.

--
With Regards,
Sandipan