On Tue, 31 May 2011 09:13:47 +0600 Rakib Mullick <rakib.mullick@xxxxxxxxx> wrote: > On Tue, May 31, 2011 at 5:38 AM, KAMEZAWA Hiroyuki > <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > On Mon, 30 May 2011 22:59:04 +0600 > > Rakib Mullick <rakib.mullick@xxxxxxxxx> wrote: > > > >> commit 468fd62ed9 (vmstats: add cond_resched() to refresh_cpu_vm_stats()) added cond_resched() in refresh_cpu_vm_stats. Purpose of that patch was to allow other threads to run in non-preemptive case. This patch, makes sure that cond_resched() gets called when !CONFIG_PREEMPT is set. In a preemptiable kernel we don't need to call cond_resched(). > >> > >> Signed-off-by: Rakib Mullick <rakib.mullick@xxxxxxxxx> > > > > Hmm, what benefit do we get by adding this extra #ifdef in the code directly ? > > Other cond_resched() callers are not guilty in !CONFIG_PREEMPT ? > > > Well, in preemptible kernel this context will get preempted if > requires, so we don't need cond_resched(). If you checkout the git log > of the mentioned commit, you'll find the explanation. It says: > "Adding a cond_resched() to allow other threads to run in the > non-preemptive > case." > IOW, my question is "why only this cond_resched() should be fixed ?" What's bad with all cond_resched() in the kernel as no-op in CONFIG_PREEMPT ? Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>