I encountered the run_timer_softirq lockup issue[1] many times during fuzz tests. We analyze __run_timers() and find the following problem. In the while loop of __run_timers(), because there are too many timers or improper timer handler functions, if the processing time of the expired timers is always greater than the time wheel's next_expiry, the function will loop infinitely. Here base on Peter's softirq_needs_break patchset[2], use the timeout/break logic jump out of the loop. [1] https://lore.kernel.org/lkml/fb8d80434b2148e78c0032c6c70a8b4d@xxxxxxxxxx/ [2] https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/log/?h=core/softirq Liu Jian (1): softirq, timer: Use softirq_needs_break() Peter Zijlstra (8): softirq: Rewrite softirq processing loop softirq: Use sched_clock() based timeout softirq: Factor loop termination condition softirq: Allow early break softirq: Context aware timeout softirq: Provide a softirq_needs_break() API softirq,net: Use softirq_needs_break() softirq,rcu: Use softirq_needs_break() Documentation/admin-guide/sysctl/net.rst | 11 +-- include/linux/interrupt.h | 5 ++ kernel/rcu/tree.c | 29 ++----- kernel/rcu/tree_nocb.h | 2 +- kernel/softirq.c | 97 +++++++++++++++--------- kernel/time/timer.c | 12 ++- net/core/dev.c | 6 +- net/core/dev.h | 1 - net/core/sysctl_net_core.c | 8 -- 9 files changed, 86 insertions(+), 85 deletions(-) -- 2.34.1
