| Message ID | 20180409122339.1709840-1-arnd@arndb.de |
|---|---|
| State | Accepted |
| Commit | bbe9a70a478129f3f9b2003415d0c36afcea210f |
| Headers | show |
| Series | tick-sched: avoid a maybe-uninitialized warning | expand |
* Arnd Bergmann <arnd@arndb.de> wrote: > The use of bitfields seems to confuse gcc, leading to a false-positive > warning in all compiler versions: > > kernel/time/tick-sched.c: In function 'tick_nohz_idle_exit': > kernel/time/tick-sched.c:538:2: error: 'now' may be used uninitialized in this function [-Werror=maybe-uninitialized] > > This introduces a temporary variable to track the flags so gcc > doesn't have to evaluate twice, eliminating the code path that > leads to the warning. > > Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85301 > Fixes: 1cae544d42d2 ("nohz: Gather tick_sched booleans under a common flag field") > Signed-off-by: Arnd Bergmann <arnd@arndb.de> Which tree is this against? There's no such commit either in -tip, upstream or in -next AFAICS. Thanks, Ingo
On Mon, Apr 9, 2018 at 6:18 PM, Ingo Molnar <mingo@kernel.org> wrote: > > * Arnd Bergmann <arnd@arndb.de> wrote: > >> The use of bitfields seems to confuse gcc, leading to a false-positive >> warning in all compiler versions: >> >> kernel/time/tick-sched.c: In function 'tick_nohz_idle_exit': >> kernel/time/tick-sched.c:538:2: error: 'now' may be used uninitialized in this function [-Werror=maybe-uninitialized] >> >> This introduces a temporary variable to track the flags so gcc >> doesn't have to evaluate twice, eliminating the code path that >> leads to the warning. >> >> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85301 >> Fixes: 1cae544d42d2 ("nohz: Gather tick_sched booleans under a common flag field") >> Signed-off-by: Arnd Bergmann <arnd@arndb.de> > > Which tree is this against? There's no such commit either in -tip, upstream or in > -next AFAICS. It's in today's linux-next. I found that it came in through Rafael's pm/linux-next tree. Arnd
On Monday, April 9, 2018 7:53:30 PM CEST Arnd Bergmann wrote: > On Mon, Apr 9, 2018 at 6:18 PM, Ingo Molnar <mingo@kernel.org> wrote: > > > > * Arnd Bergmann <arnd@arndb.de> wrote: > > > >> The use of bitfields seems to confuse gcc, leading to a false-positive > >> warning in all compiler versions: > >> > >> kernel/time/tick-sched.c: In function 'tick_nohz_idle_exit': > >> kernel/time/tick-sched.c:538:2: error: 'now' may be used uninitialized in this function [-Werror=maybe-uninitialized] > >> > >> This introduces a temporary variable to track the flags so gcc > >> doesn't have to evaluate twice, eliminating the code path that > >> leads to the warning. > >> > >> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85301 > >> Fixes: 1cae544d42d2 ("nohz: Gather tick_sched booleans under a common flag field") > >> Signed-off-by: Arnd Bergmann <arnd@arndb.de> > > > > Which tree is this against? There's no such commit either in -tip, upstream or in > > -next AFAICS. > > It's in today's linux-next. I found that it came in through Rafael's > pm/linux-next tree. That's the idle loop rework series. I'll add this patch on top of that if there are no objections. Thanks, Rafael
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 7eef9431ca24..646645e981f9 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -1143,6 +1143,7 @@ void tick_nohz_idle_restart_tick(void) void tick_nohz_idle_exit(void) { struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + bool idle_active, tick_stopped; ktime_t now; local_irq_disable(); @@ -1151,14 +1152,16 @@ void tick_nohz_idle_exit(void) WARN_ON_ONCE(ts->timer_expires_base); ts->inidle = 0; + idle_active = ts->idle_active; + tick_stopped = ts->tick_stopped; - if (ts->idle_active || ts->tick_stopped) + if (idle_active || tick_stopped) now = ktime_get(); - if (ts->idle_active) + if (idle_active) tick_nohz_stop_idle(ts, now); - if (ts->tick_stopped) + if (tick_stopped) __tick_nohz_idle_restart_tick(ts, now); local_irq_enable();
The use of bitfields seems to confuse gcc, leading to a false-positive warning in all compiler versions: kernel/time/tick-sched.c: In function 'tick_nohz_idle_exit': kernel/time/tick-sched.c:538:2: error: 'now' may be used uninitialized in this function [-Werror=maybe-uninitialized] This introduces a temporary variable to track the flags so gcc doesn't have to evaluate twice, eliminating the code path that leads to the warning. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85301 Fixes: 1cae544d42d2 ("nohz: Gather tick_sched booleans under a common flag field") Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- kernel/time/tick-sched.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) -- 2.9.0