From: Joe Perches <joe@perches.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Bart Van Assche <bart.vanassche@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Arjan van de Ven <arjan@infradead.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] timer: Fix jiffies wrap behavior of round_jiffies*()
Date: Wed, 29 May 2013 16:17:47 -0700 [thread overview]
Message-ID: <1369869467.22004.122.camel@joe-AO722> (raw)
In-Reply-To: <20130529160150.f0a498d188dc790d018200e9@linux-foundation.org>
On Wed, 2013-05-29 at 16:01 -0700, Andrew Morton wrote:
> On Tue, 21 May 2013 20:43:50 +0200 Bart Van Assche <bart.vanassche@gmail.com> wrote:
>
> > Make sure that the round_jiffies*() functions return a time that is
> > in the future when the jiffies counter is about to wrap.
>
> Actually "when the jiffies counter has recently wrapped".
>
> I assume this was found by inspection?
>
> > @@ -149,9 +149,7 @@ static unsigned long round_jiffies_common(unsigned long j, int cpu,
> > /* now that we have rounded, subtract the extra skew again */
> > j -= cpu * 3;
> > - if (j <= jiffies) /* rounding ate our timeout entirely; */
>
> This used to be a very common bug - we've weeded out many instances but
> I'm sure more still remain.
This list probably isn't comprehensive.
$ git grep -E "if\s*\((\s*jiffies\s*[\<\>]|.*[\<\>]=?\s*jiffies\b)"
drivers/acpi/acpi_pad.c: if (last_jiffies + round_robin_time * HZ < jiffies) {
drivers/acpi/acpi_pad.c: if (jiffies > expire_time) {
drivers/dma/ioat/dma_v2.c: if (jiffies > chan->timer.expires && timer_pending(&chan->timer)) {
drivers/infiniband/hw/ipath/ipath_sdma.c: if (jiffies < dd->ipath_sdma_abort_intr_timeout)
drivers/infiniband/hw/ipath/ipath_sdma.c: if (jiffies > dd->ipath_sdma_abort_jiffies) {
drivers/infiniband/ulp/ipoib/ipoib_cm.c: if (p && time_after_eq(jiffies, p->jiffies + IPOIB_CM_RX_UPDATE
drivers/infiniband/ulp/ipoib/ipoib_cm.c: if (time_before_eq(jiffies, p->jiffies + IPOIB_CM_RX_TIMEOUT))
drivers/input/misc/ati_remote2.c: if (!time_after_eq(jiffies, ar2->jiffies))
drivers/md/dm-log-userspace-base.c: else if (jiffies < limit)
drivers/misc/sgi-gru/grumain.c: if (gts->ts_steal_jiffies + GRU_STEAL_DELAY < jiffies)
drivers/net/ethernet/intel/e1000/e1000_ethtool.c: if (jiffies >= (time + 2)) {
drivers/net/ethernet/intel/e1000e/ethtool.c: if (jiffies >= (time + 20)) {
drivers/net/ethernet/micrel/ksz884x.c: if (next_jiffies < jiffies)
drivers/net/ethernet/micrel/ksz884x.c: } else if (jiffies >= hw_priv->counter[i].time) {
drivers/net/ethernet/micrel/ksz884x.c: if (hw_priv->pme_wait <= jiffies) {
drivers/net/ethernet/neterion/vxge/vxge-main.c: if (jiffies > fifo->jiffies + HZ / 100) {
drivers/net/ethernet/neterion/vxge/vxge-main.c: if (jiffies > ring->jiffies + HZ / 100) {
drivers/net/ethernet/qlogic/qlcnic/qlcnic_hw.c: if (jiffies > (QLCNIC_FILTER_AGE * HZ + time)) {
drivers/net/ethernet/qlogic/qlcnic/qlcnic_hw.c: if (jiffies > (QLCNIC_FILTER_AGE * HZ + time)) {
drivers/net/ethernet/qlogic/qlcnic/qlcnic_io.c: if (jiffies > (QLCNIC_READD_AGE * HZ + time))
drivers/net/ethernet/qlogic/qlcnic/qlcnic_io.c: if (jiffies > (QLCNIC_READD_AGE * HZ + tmp_fil->ftime))
drivers/scsi/lpfc/lpfc_scsi.c: if ((phba->last_ramp_down_time + QUEUE_RAMP_DOWN_INTERVAL) > jiffies) {
drivers/staging/bcm/InterfaceIdleMode.c: if (timeout < jiffies )
drivers/staging/lustre/include/linux/libcfs/linux/linux-prim.h: if (jiffies > expire) { \
drivers/staging/speakup/speakup_acntpc.c: if (jiffies >= jiff_max && ch == SPACE) {
drivers/staging/speakup/speakup_decext.c: if (jiffies >= jiff_max) {
drivers/staging/speakup/speakup_decpc.c: if (jiffies >= jiff_max) {
drivers/staging/speakup/speakup_dectlk.c: if (jiffies >= jiff_max) {
kernel/timer.c: if (j <= jiffies) /* rounding ate our timeout entirely; */
net/rds/ib_send.c: if (ic->i_ack_queued + HZ/2 < jiffies)
net/rds/ib_send.c: if (send->s_queued + HZ/2 < jiffies)
net/rds/iw_send.c: if (ic->i_ack_queued + HZ/2 < jiffies)
net/rds/iw_send.c: if (send->s_queued + HZ/2 < jiffies)
> We could perhaps have a checkpatch rule
> which looks for comparisons against jiffes (and any other
> time-measuring variables we can detect)
other variables like?
> and tells people to use
> time_after() and friends, or time_is_*_jiffies().
next prev parent reply other threads:[~2013-05-29 23:18 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-21 18:43 Bart Van Assche
2013-05-29 23:01 ` Andrew Morton
2013-05-29 23:17 ` Joe Perches [this message]
2013-05-29 23:38 ` Andrew Morton
2013-05-29 23:48 ` Joe Perches
2013-05-30 0:13 ` Joe Perches
2013-05-30 4:50 ` Andrew Morton
2013-05-30 6:19 ` Bart Van Assche
2013-06-28 15:12 ` [tip:timers/core] timer: Fix jiffies wrap behavior of round_jiffies_common() tip-bot for Bart Van Assche
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