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Soumya PN authored
In ftrace.c inside the function alloc_retstack_tasklist() (which will be invoked when function_graph tracing is on) the tasklist_lock is being held as reader while iterating through a list of threads. Here the lock is being held as reader with irqs disabled. The tasklist_lock is never write_locked in interrupt context so it is safe to not disable interrupts for the duration of read_lock in this block which, can be significant, given the block of code iterates through all threads. Hence changing the code to call read_lock() and read_unlock() instead of read_lock_irqsave() and read_unlock_irqrestore(). A similar change was made in commits: 8063e41d ("tracing: Change syscall_*regfunc() to check PF_KTHREAD and use for_each_process_thread()")' and 3472eaa1 ("sched: normalize_rt_tasks(): Don't use _irqsave for tasklist_lock, use task_rq_lock()")' Link: http://lkml.kernel.org/r/1463500874-77480-1-git-send-email-soumya.p.n@hpe.comSigned-off-by: Soumya PN <soumya.p.n@hpe.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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