Hi Anshuman, On Wed, May 20, 2020 at 06:52:54AM +0530, Anshuman Khandual wrote: > There is no way to proceed when requested register could not be searched in > arm64_ftr_reg[]. Requesting for a non present register would be an error as > well. Hence lets just BUG_ON() when the search fails in get_arm64_ftr_reg() > rather than checking for return value and doing the same in some individual > callers. > > But there are some callers that dont BUG_ON() upon search failure. It adds > an argument 'failsafe' that provides required switch between callers based > on whether they could proceed or not. > > Cc: Catalin Marinas <[email protected]> > Cc: Will Deacon <[email protected]> > Cc: Suzuki K Poulose <[email protected]> > Cc: Mark Brown <[email protected]> > Cc: [email protected] > Cc: [email protected] > > Signed-off-by: Anshuman Khandual <[email protected]> > --- > Applies on next-20200518 that has recent cpufeature changes from Will. > > arch/arm64/kernel/cpufeature.c | 26 +++++++++++++------------- > 1 file changed, 13 insertions(+), 13 deletions(-) > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index bc5048f152c1..62767cc540c3 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -557,7 +557,7 @@ static int search_cmp_ftr_reg(const void *id, const void > *regp) > * - NULL on failure. It is upto the caller to decide > * the impact of a failure. > */ > -static struct arm64_ftr_reg *get_arm64_ftr_reg(u32 sys_id) > +static struct arm64_ftr_reg *get_arm64_ftr_reg(u32 sys_id, bool failsafe)
Generally, I'm not a big fan of boolean arguments because they are really opaque at the callsite. It also seems bogus to me that we don't trust the caller to pass a valid sys_id, but we trust it to get "failsafe" right, which seems to mean "I promise to check the result isn't NULL before dereferencing it." So I don't see how this patch improves anything. I'd actually be more inclined to stick a WARN() in get_arm64_ftr_reg() when it returns NULL and have the callers handle NULL by returning early, getting rid of all the BUG_ONs in here. Sure, the system might end up in a funny state, but we WARN()d about it and tried to keep going (and Linus has some strong opinions on this too). Will
