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Date: Mon, 7 Feb 2022 22:43:03 +0800 From: Jia-Ju Bai <baijiaju1990@...il.com> To: davem@...emloft.net, kuba@...nel.org, grygorii.strashko@...com, vladimir.oltean@....com, vigneshr@...com, yangyingliang@...wei.com Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: [BUG] net: ti: possible deadlock in cpts_ptp_gettimeex() and cpts_overflow_check() Hello, My static analysis tool reports a possible deadlock in the ti driver in Linux 5.16: cpts_ptp_gettimeex() mutex_lock(&cpts->ptp_clk_mutex); --> Line 260 (Lock A) cpts_update_cur_time() wait_for_completion_timeout(&cpts->ts_push_complete, HZ); --> Line 210 (Wait X) cpts_overflow_check() mutex_lock(&cpts->ptp_clk_mutex); --> Line 411 (Lock A) cpts_update_cur_time() cpts_fifo_read() complete(&cpts->ts_push_complete); --> Line 142 (Wake X) When cpts_ptp_gettimeex() is executed, "Wait X" is performed by holding "Lock A". If cpts_overflow_check() is executed at this time, "Wake X" cannot be performed to wake up "Wait X" in cpts_ptp_gettimeex(), because "Lock A" has been already hold by cpts_ptp_gettimeex(), causing a possible deadlock. I find that "Wait X" is performed with a timeout, to relieve the possible deadlock; but I think this timeout can cause inefficient execution. I am not quite sure whether this possible problem is real and how to fix it if it is real. Any feedback would be appreciated, thanks :) Best wishes, Jia-Ju Bai
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