| Message ID | 1308056600-17601-1-git-send-email-santosh.shilimkar@ti.com (mailing list archive) |
|---|---|
| State | Rejected, archived |
| Headers | show |
On Tue, Jun 14, 2011 at 08:03, Santosh Shilimkar <santosh.shilimkar@ti.com> wrote: > With RCU debug options enabled, below warning is observed. > > =================================================== > [ INFO: suspicious rcu_dereference_check() usage. ] > --------------------------------------------------- > drivers/base/power/opp.c:151 invoked rcu_dereference_check() without protection! > > other info that might help us debug this: > > rcu_scheduler_active = 1, debug_locks = 1 > no locks held by swapper/1. > ... > > --------------------------------------------------- > > Fix the same by protecting it with rcu_read lock. > > Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com> > Cc: Rafael J. Wysocki <rjw@sisk.pl> > Cc: Nishanth Menon <nm@ti.com> > Cc: Kevin Hilman <khilman@deeprootsystems.com> > --- > drivers/base/power/opp.c | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c > index 56a6899..cbed5e1 100644 > --- a/drivers/base/power/opp.c > +++ b/drivers/base/power/opp.c > @@ -148,7 +148,9 @@ unsigned long opp_get_voltage(struct opp *opp) > struct opp *tmp_opp; > unsigned long v = 0; > > + rcu_read_lock(); > tmp_opp = rcu_dereference(opp); > + rcu_read_unlock(); > if (unlikely(IS_ERR_OR_NULL(tmp_opp)) || !tmp_opp->available) > pr_err("%s: Invalid parameters\n", __func__); > else NAK. please read the Documentation/power/opp.txt the usage is as follows: rcu_read_lock(); opp = opp_find_freq_ceil(); voltage = opp_get_voltage(opp); rcu_read_unlock(); the reason for this is that the opp pointer is not safe if we lock just the dereferencing. Regards, Nishanth Menon
On 6/14/2011 9:08 PM, Menon, Nishanth wrote: > On Tue, Jun 14, 2011 at 08:03, Santosh Shilimkar > <santosh.shilimkar@ti.com> wrote: >> With RCU debug options enabled, below warning is observed. >> >> =================================================== >> [ INFO: suspicious rcu_dereference_check() usage. ] >> --------------------------------------------------- >> drivers/base/power/opp.c:151 invoked rcu_dereference_check() without protection! >> >> other info that might help us debug this: >> >> rcu_scheduler_active = 1, debug_locks = 1 >> no locks held by swapper/1. >> ... >> >> --------------------------------------------------- >> >> Fix the same by protecting it with rcu_read lock. >> >> Signed-off-by: Santosh Shilimkar<santosh.shilimkar@ti.com> >> Cc: Rafael J. Wysocki<rjw@sisk.pl> >> Cc: Nishanth Menon<nm@ti.com> >> Cc: Kevin Hilman<khilman@deeprootsystems.com> >> --- >> drivers/base/power/opp.c | 2 ++ >> 1 files changed, 2 insertions(+), 0 deletions(-) >> >> diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c >> index 56a6899..cbed5e1 100644 >> --- a/drivers/base/power/opp.c >> +++ b/drivers/base/power/opp.c >> @@ -148,7 +148,9 @@ unsigned long opp_get_voltage(struct opp *opp) >> struct opp *tmp_opp; >> unsigned long v = 0; >> >> + rcu_read_lock(); >> tmp_opp = rcu_dereference(opp); >> + rcu_read_unlock(); >> if (unlikely(IS_ERR_OR_NULL(tmp_opp)) || !tmp_opp->available) >> pr_err("%s: Invalid parameters\n", __func__); >> else > NAK. please read the Documentation/power/opp.txt > the usage is as follows: > rcu_read_lock(); > opp = opp_find_freq_ceil(); > voltage = opp_get_voltage(opp); > rcu_read_unlock(); > > the reason for this is that the opp pointer is not safe if we lock > just the dereferencing. > Fair enough. if the whole fn is under the lock then it's not necessary. Regards Santosh
=================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- drivers/base/power/opp.c:151 invoked rcu_dereference_check() without protection! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 1 no locks held by swapper/1. ... --------------------------------------------------- Fix the same by protecting it with rcu_read lock. Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Cc: Rafael J. Wysocki <rjw@sisk.pl> Cc: Nishanth Menon <nm@ti.com> Cc: Kevin Hilman <khilman@deeprootsystems.com> --- drivers/base/power/opp.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c index 56a6899..cbed5e1 100644 --- a/drivers/base/power/opp.c +++ b/drivers/base/power/opp.c @@ -148,7 +148,9 @@ unsigned long opp_get_voltage(struct opp *opp) struct opp *tmp_opp; unsigned long v = 0; + rcu_read_lock(); tmp_opp = rcu_dereference(opp); + rcu_read_unlock(); if (unlikely(IS_ERR_OR_NULL(tmp_opp)) || !tmp_opp->available) pr_err("%s: Invalid parameters\n", __func__); else