U.S. stocks had modest gains.
Market continues to be volatile.
Oil slump has impact on markets.
Technology companies helped stocks rise on Wall Street.
U.S. decision to ban technology sales to China’s Huawei hurts chipmakers.
Investors’ worries about tariff dispute between U.S. and China loom over market.
Gains by tech companies, banks mark rebound from tariff worries.
Microsoft, Apple, Google lead modest rally.
S&P recovers nearly a third of loss from Monday.
Issues tumble for technology firms with interests in China.