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blk-iocost: Fix error on iocost_ioc_vrate_adj 

Systemtap 4.2 is unable to correctly interpret the "u32 (*missed_ppm)[2]"
argument of the iocost_ioc_vrate_adj trace entry defined in
include/trace/events/iocost.h leading to the following error:

  /tmp/stapAcz0G0/stap_c89c58b83cea1724e26395efa9ed4939_6321_aux_6.c:78:8:
  error: expected ‘;’, ‘,’ or ‘)’ before ‘*’ token
   , u32[]* __tracepoint_arg_missed_ppm

That argument type is indeed rather complex and hard to read. Looking
at block/blk-iocost.c. It is just a 2-entry u32 array. By simplifying
the argument to a simple "u32 *missed_ppm" and adjusting the trace
entry accordingly, the compilation error was gone.

Fixes: 7caa47151a ("blkcg: implement blk-iocost")
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Waiman Long 2020-04-21 09:07:55 -04:00 committed by Jens Axboe
parent b849dd84b6
commit d6c8e949a3
2 changed files with 5 additions and 5 deletions
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4
block/blk-iocost.c
View File

@ -1591,7 +1591,7 @@ static void ioc_timer_fn(struct timer_list *timer)
vrate_min, vrate_max);
}
trace_iocost_ioc_vrate_adj(ioc, vrate, &missed_ppm, rq_wait_pct,
trace_iocost_ioc_vrate_adj(ioc, vrate, missed_ppm, rq_wait_pct,
nr_lagging, nr_shortages,
nr_surpluses);
@ -1600,7 +1600,7 @@ static void ioc_timer_fn(struct timer_list *timer)
ioc->period_us * vrate * INUSE_MARGIN_PCT, 100);
} else if (ioc->busy_level != prev_busy_level || nr_lagging) {
trace_iocost_ioc_vrate_adj(ioc, atomic64_read(&ioc->vtime_rate),
&missed_ppm, rq_wait_pct, nr_lagging,
missed_ppm, rq_wait_pct, nr_lagging,
nr_shortages, nr_surpluses);
}

6
include/trace/events/iocost.h
View File

@ -130,7 +130,7 @@ DEFINE_EVENT(iocg_inuse_update, iocost_inuse_reset,
TRACE_EVENT(iocost_ioc_vrate_adj,
TP_PROTO(struct ioc *ioc, u64 new_vrate, u32 (*missed_ppm)[2],
TP_PROTO(struct ioc *ioc, u64 new_vrate, u32 *missed_ppm,
u32 rq_wait_pct, int nr_lagging, int nr_shortages,
int nr_surpluses),
@ -155,8 +155,8 @@ TRACE_EVENT(iocost_ioc_vrate_adj,
__entry->old_vrate = atomic64_read(&ioc->vtime_rate);;
__entry->new_vrate = new_vrate;
__entry->busy_level = ioc->busy_level;
__entry->read_missed_ppm = (*missed_ppm)[READ];
__entry->write_missed_ppm = (*missed_ppm)[WRITE];
__entry->read_missed_ppm = missed_ppm[READ];
__entry->write_missed_ppm = missed_ppm[WRITE];
__entry->rq_wait_pct = rq_wait_pct;
__entry->nr_lagging = nr_lagging;
__entry->nr_shortages = nr_shortages;