Re: [LTP] thp04: Fix PTRACE mode for CONFIG_PROC_MEM_FORCE_PTRACE=y

[linuxtestproject.agent@gmail.com]

Hi Jan,

On Wed, Jul 1, 2026 at 13:12:38 +0200, Jan Polensky wrote:
> thp04: Fix PTRACE mode for CONFIG_PROC_MEM_FORCE_PTRACE=y

> -#include "lapi/mmap.h"
> +#include "tst_checkpoint.h"
>  #include "tst_fuzzy_sync.h"
> +#include "tst_kconfig.h"
> +#include "tst_test.h"

The patch drops lapi/mmap.h but the test still uses MADV_HUGEPAGE (in
alloc_zero_page) and MADV_DONTNEED (multiple call sites). The fallback
defines for these constants live in lapi/mmap.h. On toolchains where
<sys/mman.h> does not provide them, this will fail to compile.

> +static void run_proc_mem_ptrace_race(void)
> +{
> +	/* After 1000 iterations, let tracee exit cleanly */
> +	SAFE_PTRACE(PTRACE_CONT, tracee_pid, NULL, NULL);
> +	SAFE_WAITPID(tracee_pid, &status, 0);

After run_proc_mem_ptrace_race() returns, the tracee has been reaped.
If the framework re-invokes run() (e.g. via -i 2), the next call to
SAFE_OPEN("/proc/<pid>/mem") will hit ENOENT and abort with TBROK.

The PROC_MEM_ALWAYS path survives re-invocation because
tst_fzsync_run_a() returns false immediately when runtime expires. The
ptrace path could either re-spawn the tracee in run(), or guard with
an early return when tracee_pid is no longer alive.

Verdict - Needs revision

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