On Tue, 2017-04-04 at 12:42 +0200, Paolo Valente wrote: > > Il giorno 31 mar 2017, alle ore 17:31, Bart Van Assche > > <bart.vanass...@sandisk.com> ha scritto: > > > > On Fri, 2017-03-31 at 14:47 +0200, Paolo Valente wrote: > > > + delta_ktime = ktime_get(); > > > + delta_ktime = ktime_sub(delta_ktime, bfqd->last_budget_start); > > > + delta_usecs = ktime_to_us(delta_ktime); > > > > This patch changes the type of the variable in which the result of > > ktime_to_us() > > is stored from u64 into u32 and next compares that result with LONG_MAX. > > Since > > ktime_to_us() returns a signed 64-bit number, are you sure you want to > > store that > > result in a 32-bit variable? If ktime_to_us() would e.g. return > > 0xffffffff00000100 > > or 0x100000100 then the assignment will truncate these numbers to 0x100. > > The instruction above the assignment you highlight stores in > delta_ktime the difference between 'now' and the last budget start. > The latter may have happened at most about 100 ms before 'now'. So > there should be no overflow issue.
Hello Paolo, Please double check the following code: if (delta_usecs < 1000 || delta_usecs >= LONG_MAX) Since delta_usecs is a 32-bit variable and LONG_MAX a 64-bit constant on 64-bit systems I'm not sure that code will do what it is intended to do. Thanks, Bart.
