* [LTP] [RFC PATCH] include: add two exponential backoff macros
@ 2018-04-11 10:56 Li Wang
2018-04-12 9:20 ` Cyril Hrubis
0 siblings, 1 reply; 3+ messages in thread
From: Li Wang @ 2018-04-11 10:56 UTC (permalink / raw)
To: ltp
Signed-off-by: Li Wang <liwang@redhat.com>
---
include/tst_common.h | 47 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 47 insertions(+)
diff --git a/include/tst_common.h b/include/tst_common.h
index e4466d5..4c96e6b 100644
--- a/include/tst_common.h
+++ b/include/tst_common.h
@@ -35,4 +35,51 @@
#define LTP_ALIGN(x, a) __LTP_ALIGN_MASK(x, (typeof(x))(a) - 1)
#define __LTP_ALIGN_MASK(x, mask) (((x) + (mask)) & ~(mask))
+/*
+ * Exponential backoff usleep for function repeat
+ * @FUNC: the function() which will be retried
+ * @ERET: an expected return value from the FUNC
+ */
+#define TST_RETRY_FUNC(FUNC, ERET) \
+ TST_RETRY_FUNC_WITH_EXPONENTIAL_BACKOFF(FUNC, ERET, 1)
+
+#define TST_RETRY_FUNC_WITH_EXPONENTIAL_BACKOFF(FUNC, ERET, MAX_DELAY) \
+do { int delay = 1; \
+ for (;;) { \
+ typeof(FUNC) ret = FUNC; \
+ if (ret == (typeof(FUNC))ERET) \
+ break; \
+ if (delay < MAX_DELAY * 1000000) { \
+ usleep(delay); \
+ delay *= 2; \
+ } else { \
+ tst_brk_(__FILE__, __LINE__, \
+ TBROK | TERRNO, #FUNC " failed"); \
+ } \
+ } \
+} while(0)
+
+/*
+ * Exponential backoff usleep for wating a varible change
+ * @VAR: the variable will be changed in other place
+ * @EXP: an expected value which VAR should be equal to
+ */
+#define TST_WAIT_ON_VAR(VAR, EXP) \
+ TST_WAIT_WITH_EXPONENTIAL_BACKOFF(VAR, EXP, 1)
+
+#define TST_WAIT_WITH_EXPONENTIAL_BACKOFF(VAR, EXP, MAX_DELAY) \
+do { int delay = 1; \
+ for (;;) { \
+ if (VAR == (typeof(VAR)) EXP) \
+ break; \
+ if (delay < MAX_DELAY * 1000000) { \
+ usleep(delay); \
+ delay *= 2; \
+ } else { \
+ tst_brk_(__FILE__, __LINE__, \
+ TBROK | TERRNO, #VAR " is not expected"); \
+ } \
+ } \
+} while(0)
+
#endif /* TST_COMMON_H__ */
--
1.9.3
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [LTP] [RFC PATCH] include: add two exponential backoff macros
2018-04-11 10:56 [LTP] [RFC PATCH] include: add two exponential backoff macros Li Wang
@ 2018-04-12 9:20 ` Cyril Hrubis
2018-04-13 9:27 ` Li Wang
0 siblings, 1 reply; 3+ messages in thread
From: Cyril Hrubis @ 2018-04-12 9:20 UTC (permalink / raw)
To: ltp
Hi!
> +/*
> + * Exponential backoff usleep for function repeat
> + * @FUNC: the function() which will be retried
> + * @ERET: an expected return value from the FUNC
> + */
> +#define TST_RETRY_FUNC(FUNC, ERET) \
> + TST_RETRY_FUNC_WITH_EXPONENTIAL_BACKOFF(FUNC, ERET, 1)
> +
> +#define TST_RETRY_FUNC_WITH_EXPONENTIAL_BACKOFF(FUNC, ERET, MAX_DELAY) \
That is quite a long name, I guess that we can shorten it a bit without
loosing too much clarity. Something as TST_RETRY_FN_EXP_BACKOFF()
carries all the information and is a bit shorter.
> +do { int delay = 1; \
We should at least prefix the delay with tst_ to make sure that it will
not alias with anything that has been passed to the FUNC, e.g. if the
FUNC is defined as foo_func(delay); the delay variable will be aliased
and the function will do something very unexpected.
> + for (;;) { \
> + typeof(FUNC) ret = FUNC; \
> + if (ret == (typeof(FUNC))ERET) \
> + break; \
Do we really need the (typeof(FUNC)) cast here?
> + if (delay < MAX_DELAY * 1000000) { \
> + usleep(delay); \
> + delay *= 2; \
Maybe we can be a bit more verbose and say something as:
tst_res(TINFO, #FUNC" returned %i, retrying in %ius", ret, delay);
> + } else { \
> + tst_brk_(__FILE__, __LINE__, \
> + TBROK | TERRNO, #FUNC " failed"); \
As far as I can tell we can just use the plain tst_brk() in macros since
the __LINE__ will be a constant in the whole macro and will represent
the line where the macro is called.
Also I'm not sure that adding the TERRNO here is a good idea, I suppose
that there may be a retry functions that are not seting it on a failure.
Maybe we can pass additional tst_res/tst_brk flags to the macro itself.
> + } \
> + } \
> +} while(0)
> +
> +/*
> + * Exponential backoff usleep for wating a varible change
> + * @VAR: the variable will be changed in other place
> + * @EXP: an expected value which VAR should be equal to
> + */
> +#define TST_WAIT_ON_VAR(VAR, EXP) \
> + TST_WAIT_WITH_EXPONENTIAL_BACKOFF(VAR, EXP, 1)
> +
> +#define TST_WAIT_WITH_EXPONENTIAL_BACKOFF(VAR, EXP, MAX_DELAY) \
> +do { int delay = 1; \
^
Trailing whitespace.
> + for (;;) { \
> + if (VAR == (typeof(VAR)) EXP) \
> + break; \
> + if (delay < MAX_DELAY * 1000000) { \
> + usleep(delay); \
> + delay *= 2; \
> + } else { \
> + tst_brk_(__FILE__, __LINE__, \
> + TBROK | TERRNO, #VAR " is not expected"); \
> + } \
> + } \
> +} while(0)
I would refrain from adding this function unless we have a use-case
already. Do you have a test in mind that could use this?
> #endif /* TST_COMMON_H__ */
> --
> 1.9.3
>
--
Cyril Hrubis
chrubis@suse.cz
^ permalink raw reply [flat|nested] 3+ messages in thread
* [LTP] [RFC PATCH] include: add two exponential backoff macros
2018-04-12 9:20 ` Cyril Hrubis
@ 2018-04-13 9:27 ` Li Wang
0 siblings, 0 replies; 3+ messages in thread
From: Li Wang @ 2018-04-13 9:27 UTC (permalink / raw)
To: ltp
Cyril Hrubis <chrubis@suse.cz> wrote:
> +#define TST_RETRY_FUNC_WITH_EXPONENTIAL_BACKOFF(FUNC, ERET, MAX_DELAY) \
>
> That is quite a long name, I guess that we can shorten it a bit without
> loosing too much clarity. Something as TST_RETRY_FN_EXP_BACKOFF()
> carries all the information and is a bit shorter.
>
Yes, and we can also take use this directly for looping more seconds.
> > +do { int delay = 1; \
>
> We should at least prefix the delay with tst_ to make sure that it will
> not alias with anything that has been passed to the FUNC, e.g. if the
> FUNC is defined as foo_func(delay); the delay variable will be aliased
> and the function will do something very unexpected.
>
You are right, I missed this problem.
> > + for (;;) { \
> > + typeof(FUNC) ret = FUNC; \
> > + if (ret == (typeof(FUNC))ERET) \
> > + break; \
>
> Do we really need the (typeof(FUNC)) cast here?
>
I set the type cast to ensure more safe in comparing, but it seems no
needed.
Will remove this.
> > + if (delay < MAX_DELAY * 1000000) { \
> > + usleep(delay); \
> > + delay *= 2; \
>
> Maybe we can be a bit more verbose and say something as:
>
> tst_res(TINFO, #FUNC" returned %i, retrying in %ius", ret, delay);
>
Agree.
> > + } else { \
> > + tst_brk_(__FILE__, __LINE__, \
> > + TBROK | TERRNO, #FUNC " failed"); \
>
> As far as I can tell we can just use the plain tst_brk() in macros since
> the __LINE__ will be a constant in the whole macro and will represent
> the line where the macro is called.
>
> Also I'm not sure that adding the TERRNO here is a good idea, I suppose
> that there may be a retry functions that are not seting it on a failure.
> Maybe we can pass additional tst_res/tst_brk flags to the macro itself.
>
>
Hmm, yes! But I don't want to add more flags to the macro since that will
make things more complicated for user. So, let's just abandon the TERRNO
to see how thing going on.
> > + } \
> > + } \
> > +} while(0)
> > +
> > +/*
> > + * Exponential backoff usleep for wating a varible change
> > + * @VAR: the variable will be changed in other place
> > + * @EXP: an expected value which VAR should be equal to
> > + */
> > +#define TST_WAIT_ON_VAR(VAR, EXP) \
> > + TST_WAIT_WITH_EXPONENTIAL_BACKOFF(VAR, EXP, 1)
> > +
> > +#define TST_WAIT_WITH_EXPONENTIAL_BACKOFF(VAR, EXP, MAX_DELAY) \
> > +do { int delay = 1; \
> ^
> Trailing whitespace.
> > + for (;;) { \
> > + if (VAR == (typeof(VAR)) EXP) \
> > + break; \
> > + if (delay < MAX_DELAY * 1000000) { \
> > + usleep(delay); \
> > + delay *= 2; \
> > + } else { \
> > + tst_brk_(__FILE__, __LINE__, \
> > + TBROK | TERRNO, #VAR " is not expected"); \
> > + } \
> > + } \
> > +} while(0)
>
> I would refrain from adding this function unless we have a use-case
> already. Do you have a test in mind that could use this?
>
No, I don't have any test so far, this is just came to my mind
for one situation. We could re-add it if necessary next time.
> > #endif /* TST_COMMON_H__ */
> > --
> > 1.9.3
> >
>
> --
> Cyril Hrubis
> chrubis@suse.cz
>
--
Li Wang
liwang@redhat.com
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