safe: add race test to ensure Writer's safety
safe: add race test to ensure Writer's safety

ggarnier/tsuru,firebitsbr/tsuru,ggarnier/tsuru,RichardKnop/tsuru,gciotta/tsuru,ggarnier/tsuru,tsuru/tsuru,ggarnier/tsuru,hugoantunes/tsuru,jblancett/tsuru,ArxdSilva/tsuru,tsuru/tsuru,tuxmonteiro/tsuru,gciotta/tsuru,RichardKnop/tsuru,gwmoura/tsuru,RichardKnop/tsuru,4eek/tsuru,hcxiong/tsuru,cezarsa/tsuru,mderaldo/tsuru,kgrvamsi/tsuru,tsuru/tsuru,cezarsa/tsuru,guilhermebr/tsuru,cgvarela/tsuru,Endika/tsuru,Endika/tsuru,hugoantunes/tsuru,cgvarela/tsuru,guilhermebr/tsuru,mderaldo/tsuru,cezarsa/tsuru,ArxdSilva/tsuru,firebitsbr/tsuru,4eek/tsuru,cezarsa/tsuru,Endika/tsuru,tuxmonteiro/tsuru,guilhermebr/tsuru,gciotta/tsuru,gwmoura/tsuru,hcxiong/tsuru,hcxiong/tsuru,tuxmonteiro/tsuru,jblancett/tsuru,4eek/tsuru,ArxdSilva/tsuru,kgrvamsi/tsuru,jblancett/tsuru,gwmoura/tsuru,mderaldo/tsuru,kgrvamsi/tsuru,tsuru/tsuru,firebitsbr/tsuru,guilhermebr/tsuru,cgvarela/tsuru,ArxdSilva/tsuru