Hi, On Tue, Sep 22, 2015 at 04:30:13PM -0700, David Rientjes wrote: > The oom killer takes task_lock() in a couple of places solely to protect > printing the task's comm. > > A process's comm, including current's comm, may change due to > /proc/pid/comm or PR_SET_NAME. > > The comm will always be NULL-terminated, so the worst race scenario would > only be during update. We can tolerate a comm being printed that is in > the middle of an update to avoid taking the lock. > > Other locations in the kernel have already dropped task_lock() when > printing comm, so this is consistent.
Without the protection, can't reading task->comm race with PR_SET_NAME as described below? Let T->comm[16] = "name\0rubbish1234" CPU1 CPU2 ---- ---- set_task_comm(T, "longname\0") T->comm[0] = 'l' T->comm[1] = 'o' T->comm[2] = 'n' T->comm[3] = 'g' T->comm[4] = 'n' printk("%s\n", T->comm) T->comm = "longnrubbish1234" OOPS: the string is not nil-terminated! T->comm[5] = 'a' T->comm[6] = 'm' T->comm[7] = 'e' T->comm[8] = '\0' Thanks, Vladimir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/