From: Jes Sorensen <jsoren...@fb.com> I came across this in 4.16, but I believe the bug is still present in current 5.x, even if it is less likely to trigger.
Basially stop_timer_and_thread() only calls del_timer_sync() if timer_running == true. However smi_mod_timer enables the timer before setting timer_running = true. I was able to reproduce this in 4.16 running the following on a host while :; do rmmod ipmi_si ; modprobe ipmi_si; done while rebooting the BMC on it in parallel. 5.2 moves the error handling around and does it more centralized, but relying on timer_running still seems dubious to me. static void smi_mod_timer(struct smi_info *smi_info, unsigned long new_val) { if (!smi_info->timer_can_start) return; smi_info->last_timeout_jiffies = jiffies; mod_timer(&smi_info->si_timer, new_val); smi_info->timer_running = true; } static inline void stop_timer_and_thread(struct smi_info *smi_info) { if (smi_info->thread != NULL) { kthread_stop(smi_info->thread); smi_info->thread = NULL; } smi_info->timer_can_start = false; if (smi_info->timer_running) del_timer_sync(&smi_info->si_timer); } Cheers, Jes Jes Sorensen (1): ipmi_si_intf: Fix race in timer shutdown handling drivers/char/ipmi/ipmi_si_intf.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) -- 2.21.0