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arm64: ftrace: Set FTRACE_MAY_SLEEP before ftrace_modify_all_code()

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It has been reported that ftrace_replace_code() which is called by
ftrace_modify_all_code() can cause a soft lockup warning for an
allmodconfig kernel. This is because all the debug options enabled
causes the loop in ftrace_replace_code() (which loops over all the
functions being enabled where there can be 10s of thousands), is too
slow, and never schedules out.

To solve this, setting FTRACE_MAY_SLEEP to the command passed into
ftrace_replace_code() will make it call cond_resched() in the loop,
which prevents the soft lockup warning from triggering.

Link: http://lkml.kernel.org/r/20181204192903.8193-1-anders.roxell@linaro.org
Link: http://lkml.kernel.org/r/20181205183304.000714627@goodmis.org

Acked-by: Will Deacon <will.deacon@arm.com>
Reported-by: Anders Roxell <anders.roxell@linaro.org>
Tested-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2018-12-05 12:48:54 -05:00
parent a0572f687f
commit e4c07bf986
1 changed files with 1 additions and 0 deletions
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arch/arm64/kernel/ftrace.c
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@ -193,6 +193,7 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
void arch_ftrace_update_code(int command) void arch_ftrace_update_code(int command)
{ {
command |= FTRACE_MAY_SLEEP;
ftrace_modify_all_code(command); ftrace_modify_all_code(command);
} }