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| author | Soumya PN <soumya.p.n@hpe.com> | 2016-05-17 21:31:14 +0530 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2016-05-20 13:19:37 -0400 |
| commit | 6112a300c9e41993cc0dc56ac393743d28381284 (patch) | |
| tree | bfc725d59bb98e3726c6884add2445c233c64eb7 /Documentation | |
| parent | 91e6f1ce8657795cec83a81090c20cbaa8337c68 (diff) | |
ftrace: Don't disable irqs when taking the tasklist_lock read_lock
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: 8063e41d2ffc ("tracing: Change
syscall_*regfunc() to check PF_KTHREAD and use for_each_process_thread()")'
and 3472eaa1f12e ("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.com
Signed-off-by: Soumya PN <soumya.p.n@hpe.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'Documentation')