| Message ID | 1550609234-40861-1-git-send-email-liujian56@huawei.com |
|---|---|
| State | Superseded |
| Delegated to: | Vignesh R |
| Headers | show |
| Series | [v2] cfi: fix deadloop in cfi_cmdset_0002.c do_write_buffer | expand |
On 20/02/19 2:17 AM, Liu Jian wrote: > In function do_write_buffer(), in the for loop, there is a case > chip_ready() returns 1 while chip_good() returns 0, so it never > break the loop. > To fix this, chip_good() is enough and it should timeout if it stay > bad for a while. > > Fixes: dfeae1073583 ("mtd: cfi_cmdset_0002: Change write buffer to check correct value") > Signed-off-by: Yi Huaijie <yihuaijie@huawei.com> > Signed-off-by: Liu Jian <liujian56@huawei.com> > Reviewed-by: Tokunori Ikegami <ikegami_to@yahoo.co.jp> > --- > v1->v2: > change git log, put the Fixes tag on a single line > > drivers/mtd/chips/cfi_cmdset_0002.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c > index 72428b6..818e94b 100644 > --- a/drivers/mtd/chips/cfi_cmdset_0002.c > +++ b/drivers/mtd/chips/cfi_cmdset_0002.c > @@ -1876,14 +1876,14 @@ static int __xipram do_write_buffer(struct map_info *map, struct flchip *chip, > continue; > } > > - if (time_after(jiffies, timeo) && !chip_ready(map, adr)) > - break; > - > if (chip_good(map, adr, datum)) { > xip_enable(map, chip, adr); > goto op_done; > } > > + if (time_after(jiffies, timeo)) > + break; > + It is quite possible that this thread might be pre-empted just after chip_good() check but before before time_after(). If the thread, then resumes execution after timeo has elasped then, this code will wrongly indicate write failure. To avoid this case, you should add one more check for check_good() even when time_after() returns true. Something like: if (time_after(jiffies, timeo)) { if (chip_good(map, adr, datum)) { xip_enable(map, chip, adr); goto op_done; } break; } > /* Latency issues. Drop the lock, wait a while and retry */ > UDELAY(map, chip, adr, 1); > } >
On 22-Feb-19 8:20 PM, liujian (CE) wrote: > >> -----Original Message----- >> From: Vignesh R [mailto:vigneshr@ti.com] >> Sent: Friday, February 22, 2019 1:59 PM >> To: liujian (CE) <liujian56@huawei.com>; dwmw2@infradead.org; >> computersforpeace@gmail.com; bbrezillon@kernel.org; >> marek.vasut@gmail.com; richard@nod.at; joakim.tjernlund@infinera.com; >> ikegami@allied-telesis.co.jp; keescook@chromium.org >> Cc: linux-mtd@lists.infradead.org; linux-kernel@vger.kernel.org >> Subject: Re: [PATCH v2] cfi: fix deadloop in cfi_cmdset_0002.c do_write_buffer >> >> >> >> On 20/02/19 2:17 AM, Liu Jian wrote: >>> In function do_write_buffer(), in the for loop, there is a case >>> chip_ready() returns 1 while chip_good() returns 0, so it never break >>> the loop. >>> To fix this, chip_good() is enough and it should timeout if it stay >>> bad for a while. >>> >>> Fixes: dfeae1073583 ("mtd: cfi_cmdset_0002: Change write buffer to >>> check correct value") >>> Signed-off-by: Yi Huaijie <yihuaijie@huawei.com> >>> Signed-off-by: Liu Jian <liujian56@huawei.com> >>> Reviewed-by: Tokunori Ikegami <ikegami_to@yahoo.co.jp> >>> --- >>> v1->v2: >>> change git log, put the Fixes tag on a single line >>> >>> drivers/mtd/chips/cfi_cmdset_0002.c | 6 +++--- >>> 1 file changed, 3 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c >>> b/drivers/mtd/chips/cfi_cmdset_0002.c >>> index 72428b6..818e94b 100644 >>> --- a/drivers/mtd/chips/cfi_cmdset_0002.c >>> +++ b/drivers/mtd/chips/cfi_cmdset_0002.c >>> @@ -1876,14 +1876,14 @@ static int __xipram do_write_buffer(struct >> map_info *map, struct flchip *chip, >>> continue; >>> } >>> >>> - if (time_after(jiffies, timeo) && !chip_ready(map, adr)) >>> - break; >>> - >>> if (chip_good(map, adr, datum)) { >>> xip_enable(map, chip, adr); >>> goto op_done; >>> } >>> >>> + if (time_after(jiffies, timeo)) >>> + break; >>> + >> >> It is quite possible that this thread might be pre-empted just after >> chip_good() check but before before time_after(). If the thread, then resumes >> execution after timeo has elasped then, this code will wrongly indicate write >> failure. >> >> To avoid this case, you should add one more check for check_good() even when >> time_after() returns true. Something like: >> >> if (time_after(jiffies, timeo)) { >> if (chip_good(map, adr, datum)) { >> xip_enable(map, chip, adr); >> goto op_done; >> } >> break; >> } >> > So, the patch should like this ? > > diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c > index 72428b6..3da2376 100644 > --- a/drivers/mtd/chips/cfi_cmdset_0002.c > +++ b/drivers/mtd/chips/cfi_cmdset_0002.c > @@ -1876,7 +1876,7 @@ static int __xipram do_write_buffer(struct map_info *map, struct flchip *chip, > continue; > } > > - if (time_after(jiffies, timeo) && !chip_ready(map, adr)) > + if (time_after(jiffies, timeo) && !chip_good(map, adr, datum)) > break; > > if (chip_good(map, adr, datum)) { > > > > Any other opinions? > If there are no other comments, I will send a patch again Looks fine to me.. Please submit a new version. Thanks! Regards Vignesh
diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c index 72428b6..818e94b 100644 --- a/drivers/mtd/chips/cfi_cmdset_0002.c +++ b/drivers/mtd/chips/cfi_cmdset_0002.c @@ -1876,14 +1876,14 @@ static int __xipram do_write_buffer(struct map_info *map, struct flchip *chip, continue; } - if (time_after(jiffies, timeo) && !chip_ready(map, adr)) - break; - if (chip_good(map, adr, datum)) { xip_enable(map, chip, adr); goto op_done; } + if (time_after(jiffies, timeo)) + break; + /* Latency issues. Drop the lock, wait a while and retry */ UDELAY(map, chip, adr, 1); }
In function do_write_buffer(), in the for loop, there is a case chip_ready() returns 1 while chip_good() returns 0, so it never break the loop. To fix this, chip_good() is enough and it should timeout if it stay bad for a while. Fixes: dfeae1073583 ("mtd: cfi_cmdset_0002: Change write buffer to check correct value") Signed-off-by: Yi Huaijie <yihuaijie@huawei.com> Signed-off-by: Liu Jian <liujian56@huawei.com> Reviewed-by: Tokunori Ikegami <ikegami_to@yahoo.co.jp> --- v1->v2: change git log, put the Fixes tag on a single line drivers/mtd/chips/cfi_cmdset_0002.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)