Messages in this thread | | | Date | Fri, 30 Oct 2020 10:13:50 +0100 (CET) | From | Miroslav Benes <> | Subject | Re: [PATCH 1/9] ftrace: Move the recursion testing into global headers |
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Hi,
> +static __always_inline int trace_get_context_bit(void) > +{ > + int bit; > + > + if (in_interrupt()) { > + if (in_nmi()) > + bit = 0; > + > + else if (in_irq()) > + bit = 1; > + else > + bit = 2; > + } else > + bit = 3; > + > + return bit; > +} > + > +static __always_inline int trace_test_and_set_recursion(int start, int max) > +{ > + unsigned int val = current->trace_recursion; > + int bit; > + > + /* A previous recursion check was made */ > + if ((val & TRACE_CONTEXT_MASK) > max) > + return 0; > + > + bit = trace_get_context_bit() + start; > + if (unlikely(val & (1 << bit))) > + return -1; > + > + val |= 1 << bit; > + current->trace_recursion = val; > + barrier(); > + > + return bit; > +}
how does this work in case of NMI? trace_get_context_bit() returns 0 (it does not change later in the patch set). "start" in trace_test_and_set_recursion() is 0 zero too as used later in the patch set by ftrace_test_recursion_trylock(). So trace_test_and_set_recursion() returns 0. That is perfectly sane, but then...
> +static __always_inline void trace_clear_recursion(int bit) > +{ > + unsigned int val = current->trace_recursion; > + > + if (!bit) > + return;
... the bit is not cleared here.
> + bit = 1 << bit; > + val &= ~bit; > + > + barrier(); > + current->trace_recursion = val; > +}
Thanks Miroslav
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