On Fri, 30 Nov 2018 16:09:56 +0100 Anders Roxell <anders.rox...@linaro.org> wrote:
> Both of those functions end up calling ftrace_modify_code(), which is > expensive because it changes the page tables and flush caches. > Microseconds add up because this is called in a loop for each dyn_ftrace > record, and this triggers the softlockup watchdog unless we let it sleep > occasionally. > Rework so that we call cond_resched() before going into the > ftrace_modify_code() function. > > Co-developed-by: Arnd Bergmann <a...@arndb.de> > Signed-off-by: Arnd Bergmann <a...@arndb.de> > Signed-off-by: Anders Roxell <anders.rox...@linaro.org> I'm fine with this patch, but I'm not placing an ack on this patch just because I don't know the repercussions of such a change. I'll let you folks take full responsibility ;-) -- Steve > --- > arch/arm64/kernel/ftrace.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c > index de1a397d2d3f..9da38da58df7 100644 > --- a/arch/arm64/kernel/ftrace.c > +++ b/arch/arm64/kernel/ftrace.c > @@ -130,6 +130,11 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned > long addr) > old = aarch64_insn_gen_nop(); > new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK); > > + /* This function can take a long time when sanitizers are enabled, so > + * lets make sure we allow RCU processing. > + */ > + cond_resched(); > + > return ftrace_modify_code(pc, old, new, true); > } > > @@ -188,6 +193,11 @@ int ftrace_make_nop(struct module *mod, struct > dyn_ftrace *rec, > > new = aarch64_insn_gen_nop(); > > + /* This function can take a long time when sanitizers are enabled, so > + * lets make sure we allow RCU processing. > + */ > + cond_resched(); > + > return ftrace_modify_code(pc, old, new, validate); > } >
