From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753446AbYIJJbF (ORCPT ); Wed, 10 Sep 2008 05:31:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751729AbYIJJay (ORCPT ); Wed, 10 Sep 2008 05:30:54 -0400 Received: from mx2.redhat.com ([66.187.237.31]:34325 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751650AbYIJJay (ORCPT ); Wed, 10 Sep 2008 05:30:54 -0400 Subject: Re: [PATCH] make setpriority POSIX compliant; introduce PRIO_THREAD extension From: Denys Vlasenko To: Michael Kerrisk Cc: linux-kernel@vger.kernel.org, Andrew Morton , Ulrich Drepper , Peter Zijlstra In-Reply-To: <517f3f820809090845o5dc772f8r2308a6c010f69561@mail.gmail.com> References: <1220278355.3866.21.camel@localhost.localdomain> <517f3f820809090845o5dc772f8r2308a6c010f69561@mail.gmail.com> Content-Type: text/plain Date: Wed, 10 Sep 2008 11:28:14 +0200 Message-Id: <1221038894.8848.9.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2008-09-09 at 17:45 +0200, Michael Kerrisk wrote: > > Patch is run tested. I will post test program etc as a reply. > > Tested-by: Michael Kerrisk > > Please do CC me on API changes, so that they might get documented in > the man pages. > > Thanks for this work. (I'm not sure whether or not it's a response to > my bug report, http://bugzilla.kernel.org/show_bug.cgi?id=6258 ) I worked on it because of this bug report: https://bugzilla.redhat.com/show_bug.cgi?id=455251 > I tested your patch. Most things seem to work as I would expect, but > there is one strangeness. > > I would expect > setpriority(PRIO_PROCESS, getpid()) > and > setpriority(PRIO_PROCESS, 0) > to have the same affect (because: which == PRIO_PRCESS, who == 0 > conventionally means "the calling process"). > > But they do not: the latter call only changes the priority of the > calling thread. Is this intended? No, it was not intended. I think this error is here: + case PRIO_PROCESS: + if (who) + pid = find_vpid(who); + else { + pid = task_pid(current); + who = current->pid; + } I was confused. ->pid is TID, had to use ->tgid to get PID. The fix: replace who = current->pid; with who = current->tgid; There are two places where you need to do it. Updated patch is below. Signed-off-by: Denys Vlasenko -- vda diff --git a/include/linux/resource.h b/include/linux/resource.h index aaa423a..f292690 100644 --- a/include/linux/resource.h +++ b/include/linux/resource.h @@ -51,6 +51,7 @@ struct rlimit { #define PRIO_PROCESS 0 #define PRIO_PGRP 1 #define PRIO_USER 2 +#define PRIO_THREAD 3 /* * Limit the stack by to some sane default: root can always diff --git a/kernel/sys.c b/kernel/sys.c index 038a7bc..d339c1a 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -142,9 +142,9 @@ asmlinkage long sys_setpriority(int which, int who, int niceval) struct task_struct *g, *p; struct user_struct *user; int error = -EINVAL; - struct pid *pgrp; + struct pid *pgrp, *pid; - if (which > PRIO_USER || which < PRIO_PROCESS) + if (which > PRIO_THREAD || which < PRIO_PROCESS) goto out; /* normalize: avoid signed division (rounding problems) */ @@ -156,7 +156,7 @@ asmlinkage long sys_setpriority(int which, int who, int niceval) read_lock(&tasklist_lock); switch (which) { - case PRIO_PROCESS: + case PRIO_THREAD: if (who) p = find_task_by_vpid(who); else @@ -164,6 +164,19 @@ asmlinkage long sys_setpriority(int which, int who, int niceval) if (p) error = set_one_prio(p, niceval, error); break; + case PRIO_PROCESS: + if (who) + pid = find_vpid(who); + else { + pid = task_pid(current); + who = current->tgid; + } + do_each_pid_thread(pid, PIDTYPE_PID, p) { + if (who == p->pid || who == p->tgid) { + error = set_one_prio(p, niceval, error); + } + } while_each_pid_thread(pid, PIDTYPE_PID, p); + break; case PRIO_PGRP: if (who) pgrp = find_vpid(who); @@ -206,14 +219,14 @@ asmlinkage long sys_getpriority(int which, int who) struct task_struct *g, *p; struct user_struct *user; long niceval, retval = -ESRCH; - struct pid *pgrp; + struct pid *pgrp, *pid; - if (which > PRIO_USER || which < PRIO_PROCESS) + if (which > PRIO_THREAD || which < PRIO_PROCESS) return -EINVAL; read_lock(&tasklist_lock); switch (which) { - case PRIO_PROCESS: + case PRIO_THREAD: if (who) p = find_task_by_vpid(who); else @@ -224,6 +237,21 @@ asmlinkage long sys_getpriority(int which, int who) retval = niceval; } break; + case PRIO_PROCESS: + if (who) + pid = find_vpid(who); + else { + pid = task_pid(current); + who = current->tgid; + } + do_each_pid_thread(pid, PIDTYPE_PID, p) { + if (who == p->pid || who == p->tgid) { + niceval = 20 - task_nice(p); + if (niceval > retval) + retval = niceval; + } + } while_each_pid_thread(pid, PIDTYPE_PID, p); + break; case PRIO_PGRP: if (who) pgrp = find_vpid(who);