  We present preliminary results for an updated extraction of the transversity
parton distribution based on the analysis of pion-pair production in
deep-inelastic scattering off transversely polarized targets in collinear
factorization. Data for proton and deuteron targets by HERMES and COMPASS allow
for a flavor separation of the valence components of transversity, while
di-hadron fragmentation functions are taken from the semi-inclusive production
of two pion pairs in back-to-back jets in $e^+ e^-$ annihilation. The latter
data from Belle have been reanalyzed using the replica method and a more
realistic estimate of the uncertainties on the chiral-odd interference
fragmentation function has been obtained. After encoding this piece of
information into the deep-inelastic scattering cross section, the transversity
has been re-extracted by using the most recent and more precise COMPASS data
for proton target. This picture represents the current most realistic estimate
of the uncertainties on our knowledge of transversity. The preliminary results
indicate that the valence up component seems smaller and with a narrower error
band than in previous extraction.
