usleep_range() min==max makes little sense at last for non-RT, so issue a warning if delta is 0.
Signed-off-by: Nicholas Mc Guire <hof...@osadl.org> --- As of 4.9.0 this finds about 20 cases - all of which look like the should be passing a range. Patch is against 4.9.0 (localversion-next is next-20161213) scripts/coccinelle/api/bad_usleep_range.cocci | 55 +++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) create mode 100644 scripts/coccinelle/api/bad_usleep_range.cocci diff --git a/scripts/coccinelle/api/bad_usleep_range.cocci b/scripts/coccinelle/api/bad_usleep_range.cocci new file mode 100644 index 0000000..7e05f3e --- /dev/null +++ b/scripts/coccinelle/api/bad_usleep_range.cocci @@ -0,0 +1,55 @@ +/// bad uslee_range - warn if min == max +// +//The problem is that usleep_range is calculating the delay by +// exp = ktime_add_us(ktime_get(), min) +// delta = (u64)(max - min) * NSEC_PER_USEC +//so delta is set to 0 if min==max +//and then calls +// schedule_hrtimeout_range(exp, 0,...) +//effectively this means that the clock subsystem has no room to +//optimize. usleep_range() is in non-atomic context so a 0 range +//makes very little sense as the task can be preempted anyway so +//there is no guarantee that the 0 range would be adding much +//precision - it just removes optimization potential, so it probably +//never really makes sense for any non-RT systems. +// +//see: Documentation/timers/timers-howto.txt and +//Link: http://lkml.org/lkml/2016/11/29/54 for some notes on +// when mdelay might not be a suitable replacement +// +// Confidence: Moderate +// Copyright: (C) 2016 Nicholas Mc Guire, OSADL. GPLv2. +// Comments: +// Options: --no-includes --include-headers + +virtual org +virtual report + +@nullrange@ +expression E; +constant C; +position p; +@@ + +<+... +( + usleep_range@p(C,C) +| + usleep_range@p(E,E) +) +...+> + + +@script:python depends on org@ +p << nullrange.p; +range << nullrange.C; +@@ + +cocci.print_main("WARNING: inefficient usleep_range with range 0 (min==max)",p) + +@script:python depends on report@ +p << nullrange.p; +@@ + +coccilib.report.print_report(p[0],"WARNING: inefficient usleep_range with range 0 (min==max)") + -- 2.1.4 _______________________________________________ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
