| Message ID | 1341407737-1016-1-git-send-email-pgaikwad@nvidia.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wednesday 04 July 2012 06:45 PM, Prashant Gaikwad wrote: > Compiler optimizes code someway that even if clk->parents > is not NULL it tries to allocate parents array. Change the > condition so that compiler does not optimize it in wrong > way. > > Also, initialize i to num_parents to make sure parent > is searched using parent name if parents is NULL. > > Signed-off-by: Prashant Gaikwad<pgaikwad@nvidia.com> > --- > Mike, > > There could be some other way to fix problem. I have not > debugged it in detail but I think this simple change should do. Mike, Please ignore this patch as Rajendra has already sent patch to fix. http://git.linaro.org/gitweb?p=people/mturquette/linux.git;a=commitdiff;h=863b13271f1608ab3af6f7a371047d9a66693e38 > drivers/clk/clk.c | 10 +++++----- > 1 files changed, 5 insertions(+), 5 deletions(-) >
On 07/04/2012 07:15 AM, Prashant Gaikwad wrote: > Compiler optimizes code someway that even if clk->parents > is not NULL it tries to allocate parents array. Change the > condition so that compiler does not optimize it in wrong > way. If simply inverting the if test and swapping the if/else blocks solves some problem, that sounds like a compiler bug that we need to track down and file/fix. > Also, initialize i to num_parents to make sure parent > is searched using parent name if parents is NULL. Are you sure the change to initialize i wasn't all that was required to solve the problem though? Mike has applied a patch for this that'll be applied to 3.5-rcX and hence trickle into 3.6.
On Thursday 05 July 2012 09:37 PM, Stephen Warren wrote: > On 07/04/2012 07:15 AM, Prashant Gaikwad wrote: >> Compiler optimizes code someway that even if clk->parents >> is not NULL it tries to allocate parents array. Change the >> condition so that compiler does not optimize it in wrong >> way. > If simply inverting the if test and swapping the if/else blocks solves > some problem, that sounds like a compiler bug that we need to track down > and file/fix. > >> Also, initialize i to num_parents to make sure parent >> is searched using parent name if parents is NULL. > Are you sure the change to initialize i wasn't all that was required to > solve the problem though? Mike has applied a patch for this that'll be > applied to 3.5-rcX and hence trickle into 3.6. Just initializing i does not fix problem. The patch Mike has applied does two things 1. remove warning for uninitialized i 2. invert the if test
On 07/05/2012 11:21 AM, Prashant Gaikwad wrote: > On Thursday 05 July 2012 09:37 PM, Stephen Warren wrote: >> On 07/04/2012 07:15 AM, Prashant Gaikwad wrote: >>> Compiler optimizes code someway that even if clk->parents >>> is not NULL it tries to allocate parents array. Change the >>> condition so that compiler does not optimize it in wrong >>> way. >> If simply inverting the if test and swapping the if/else blocks solves >> some problem, that sounds like a compiler bug that we need to track down >> and file/fix. >> >>> Also, initialize i to num_parents to make sure parent >>> is searched using parent name if parents is NULL. >> Are you sure the change to initialize i wasn't all that was required to >> solve the problem though? Mike has applied a patch for this that'll be >> applied to 3.5-rcX and hence trickle into 3.6. > > Just initializing i does not fix problem. The patch Mike has applied > does two things > 1. remove warning for uninitialized i > 2. invert the if test Yes, but Mike's patch is very different to yours. Your patch description says that you need to invert the if test to work around the compiler optimizer so that it doesn't "optimize it in wrong way", whereas the patch Mike applied was for a legitimate bug in the code; those are two entirely different things.
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index 026d901..b28f2ae 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -1066,18 +1066,18 @@ static int __clk_set_parent(struct clk *clk, struct clk *parent) struct clk *old_parent; unsigned long flags; int ret = -EINVAL; - u8 i; + u8 i = clk->num_parents; old_parent = clk->parent; /* find index of new parent clock using cached parent ptrs */ - if (clk->parents) + if (!clk->parents) + clk->parents = kzalloc((sizeof(struct clk*) * clk->num_parents), + GFP_KERNEL); + else for (i = 0; i < clk->num_parents; i++) if (clk->parents[i] == parent) break; - else - clk->parents = kzalloc((sizeof(struct clk*) * clk->num_parents), - GFP_KERNEL); /* * find index of new parent clock using string name comparison
Compiler optimizes code someway that even if clk->parents is not NULL it tries to allocate parents array. Change the condition so that compiler does not optimize it in wrong way. Also, initialize i to num_parents to make sure parent is searched using parent name if parents is NULL. Signed-off-by: Prashant Gaikwad <pgaikwad@nvidia.com> --- Mike, There could be some other way to fix problem. I have not debugged it in detail but I think this simple change should do. drivers/clk/clk.c | 10 +++++----- 1 files changed, 5 insertions(+), 5 deletions(-)