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U2FsdGVkX18ZRhren1xr5yjC3J81Ezwfm2F9ijkYGWCgJsZhk5a/KQrOCQ3tZCE08lQDIFJBl0XIpEZVebzmlu1EDxaptm+sjiVvZ1cA1ACJeELxOvAz54MvDCvwdRLh9hjv5Qby3cpQ+KtAJgFE9FpsS1Eiz5tMJilEQ8+bpa7u4wXiUQYN7ZQ7ACCE9UJ1l5zq9zifHhXaxhc4sz4mGmq8acxoX+A5OSZMIh0FOFvYOPs693895g1Nds5PWk31iFaLo07ppoVT7W7ITHDYp3S+xnmlWYh4r+967wv+WfJS0scyrWB6t+tMHTTHBtggo7ON/Qo4UZ4aMG72rYSiVViZyA61UQ2FzW29oqVBmmhneg0Dj1qRgMilt1SLK02+z21mSQ0jcOM7AO4iXSXX7+KY6QCxWfJdNeK1OJ/FZgO9jgPZd2MWZPeo5OAJg6lwXHIJ5uUwiXcvs36vFTx2Z4nLF/CGC0McY3VQn2wZUePt8KDAM/w8o8QRFcrW8t3ZTHQmdGoskT9i1kAoJMFcMoV8Cqb0gfKsnjZp+oHoB+EKxVTFQ1BZz/h5cXidgeBa7KeDhvUz+9wNloqnFsXVs6gQzes4t5SShE6HstvEjoTq1YApYk0bDcO8zTWeLcxBJ5votNX+wRBofLmLqwnpJFr/SZy8yHYXj25/z3s8L2RCrwFEBWkt76gt8WFlGwpQma4tiHWzG7HAjmwSPhOP/7mCqS2ZyzZgG7z4LV3VigRUdrtfnGIK2ihGGuXCjAE1AxM09d8+4r2NdPoQP51gaTNRYp7zhYURFVNhOWH906tOrPQBocOCgy5KAFMS0vIX1yWAnIk2lfKSEV12RrNmFLiK0bq62NhE+TEzpTDofgZQXee+sC9VyCafR8qLdGMqauE9hJTlMUebOGu8zEbkSEPMWvYLutclYp5clFsMo2pAB6M/aB6P9/BlaJHVatsBW3ssmWpPVF418oHTFT9 4W65xnB6 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This was necessary because lacking preempt_count, there was no way for the tick handler to know if we were executing in RCU read-side critical section or not. An always-on CONFIG_PREEMPT_COUNT, however, allows the tick to reliably report quiescent states. Accordingly, evaluate preempt_count() based quiescence in rcu_flavor_sched_clock_irq(). Suggested-by: Paul E. McKenney Signed-off-by: Ankur Arora --- kernel/rcu/tree_plugin.h | 3 ++- kernel/sched/core.c | 15 +-------------- 2 files changed, 3 insertions(+), 15 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index f87191e008ff..618f055f8028 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -963,7 +963,8 @@ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) */ static void rcu_flavor_sched_clock_irq(int user) { - if (user || rcu_is_cpu_rrupt_from_idle()) { + if (user || rcu_is_cpu_rrupt_from_idle() || + !(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK))) { /* * Get here if this CPU took its interrupt from user diff --git a/kernel/sched/core.c b/kernel/sched/core.c index bf5df2b866df..15db5fb7acc7 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8588,20 +8588,7 @@ int __sched _cond_resched(void) preempt_schedule_common(); return 1; } - /* - * In preemptible kernels, ->rcu_read_lock_nesting tells the tick - * whether the current CPU is in an RCU read-side critical section, - * so the tick can report quiescent states even for CPUs looping - * in kernel context. In contrast, in non-preemptible kernels, - * RCU readers leave no in-memory hints, which means that CPU-bound - * processes executing in kernel context might never report an - * RCU quiescent state. Therefore, the following code causes - * cond_resched() to report a quiescent state, but only when RCU - * is in urgent need of one. - */ -#ifndef CONFIG_PREEMPT_RCU - rcu_all_qs(); -#endif + return 0; } EXPORT_SYMBOL(_cond_resched);