Re: lib: Use backoff polling to wait for loop device nodes

Hi Wake,

On Aug 5, 2026, Wake Liu wrote:
> lib: Use backoff polling to wait for loop device nodes

> +				path_set = TST_RETRY_FN_EXP_BACKOFF(
> +					set_dev_loop_path(rc, path, path_len),
> +					TST_RETVAL_EQ0, 1);

Could the declaration of tst_multiply_timeout() be made available to this
legacy-API library, or could polling avoid this macro? The macro expands to a
call to tst_multiply_timeout(), but test.h does not declare it. GCC reports an
implicit declaration and Clang rejects both new call sites under C99:

> error: call to undeclared function 'tst_multiply_timeout'; ISO C99 and later do not support implicit function declarations

> tst_find_free_loopdev() and tst_attach_device() (starting at 1ms delay,
> doubling each try, capped at 100ms) to wait for the device node to be
> successfully populated.

Could this timing description be corrected or the requested timing be
implemented? TST_RETRY_FN_EXP_BACKOFF(..., 1) starts at one microsecond and
uses one second as its maximum-delay threshold, subject to
tst_multiply_timeout().

Verdict - Needs revision

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