<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux.git/drivers/tty/serial, branch v3.9-rc2</title>
<subtitle>Linux kernel source tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/'/>
<entry>
<title>Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus</title>
<updated>2013-03-02T15:44:16+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2013-03-02T15:44:16+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=aebb2afd5420c860b7fbc3882a323ef1247fbf16'/>
<id>aebb2afd5420c860b7fbc3882a323ef1247fbf16</id>
<content type='text'>
Pull MIPS updates from Ralf Baechle:

 o Add basic support for the Mediatek/Ralink Wireless SoC family.

 o The Qualcomm Atheros platform is extended by support for the new
   QCA955X SoC series as well as a bunch of patches that get the code
   ready for OF support.

 o Lantiq and BCM47XX platform have a few improvements and bug fixes.

 o MIPS has sent a few patches that get the kernel ready for the
   upcoming microMIPS support.

 o The rest of the series is made up of small bug fixes and cleanups
   that relate to various parts of the MIPS code.  The biggy in there is
   a whitespace cleanup.  After I was sent another set of whitespace
   cleanup patches I decided it was the time to clean the whitespace
   "issues" for once and and that touches many files below arch/mips/.

Fix up silly conflicts, mostly due to whitespace cleanups.

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: (105 commits)
  MIPS: Quit exporting kernel internel break codes to uapi/asm/break.h
  MIPS: remove broken conditional inside vpe loader code
  MIPS: SMTC: fix implicit declaration of set_vi_handler
  MIPS: early_printk: drop __init annotations
  MIPS: Probe for and report hardware virtualization support.
  MIPS: ath79: add support for the Qualcomm Atheros AP136-010 board
  MIPS: ath79: add USB controller registration code for the QCA955X SoCs
  MIPS: ath79: add PCI controller registration code for the QCA955X SoCs
  MIPS: ath79: add WMAC registration code for the QCA955X SoCs
  MIPS: ath79: register UART for the QCA955X SoCs
  MIPS: ath79: add QCA955X specific glue to ath79_device_reset_{set, clear}
  MIPS: ath79: add GPIO setup code for the QCA955X SoCs
  MIPS: ath79: add IRQ handling code for the QCA955X SoCs
  MIPS: ath79: add clock setup code for the QCA955X SoCs
  MIPS: ath79: add SoC detection code for the QCA955X SoCs
  MIPS: ath79: add early printk support for the QCA955X SoCs
  MIPS: ath79: fix WMAC IRQ resource assignment
  mips: reserve elfcorehdr
  mips: Make sure kernel memory is in iomem
  MIPS: ath79: use dynamically allocated USB platform devices
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull MIPS updates from Ralf Baechle:

 o Add basic support for the Mediatek/Ralink Wireless SoC family.

 o The Qualcomm Atheros platform is extended by support for the new
   QCA955X SoC series as well as a bunch of patches that get the code
   ready for OF support.

 o Lantiq and BCM47XX platform have a few improvements and bug fixes.

 o MIPS has sent a few patches that get the kernel ready for the
   upcoming microMIPS support.

 o The rest of the series is made up of small bug fixes and cleanups
   that relate to various parts of the MIPS code.  The biggy in there is
   a whitespace cleanup.  After I was sent another set of whitespace
   cleanup patches I decided it was the time to clean the whitespace
   "issues" for once and and that touches many files below arch/mips/.

Fix up silly conflicts, mostly due to whitespace cleanups.

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: (105 commits)
  MIPS: Quit exporting kernel internel break codes to uapi/asm/break.h
  MIPS: remove broken conditional inside vpe loader code
  MIPS: SMTC: fix implicit declaration of set_vi_handler
  MIPS: early_printk: drop __init annotations
  MIPS: Probe for and report hardware virtualization support.
  MIPS: ath79: add support for the Qualcomm Atheros AP136-010 board
  MIPS: ath79: add USB controller registration code for the QCA955X SoCs
  MIPS: ath79: add PCI controller registration code for the QCA955X SoCs
  MIPS: ath79: add WMAC registration code for the QCA955X SoCs
  MIPS: ath79: register UART for the QCA955X SoCs
  MIPS: ath79: add QCA955X specific glue to ath79_device_reset_{set, clear}
  MIPS: ath79: add GPIO setup code for the QCA955X SoCs
  MIPS: ath79: add IRQ handling code for the QCA955X SoCs
  MIPS: ath79: add clock setup code for the QCA955X SoCs
  MIPS: ath79: add SoC detection code for the QCA955X SoCs
  MIPS: ath79: add early printk support for the QCA955X SoCs
  MIPS: ath79: fix WMAC IRQ resource assignment
  mips: reserve elfcorehdr
  mips: Make sure kernel memory is in iomem
  MIPS: ath79: use dynamically allocated USB platform devices
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux into mips-for-linux-next</title>
<updated>2013-02-22T09:07:30+00:00</updated>
<author>
<name>Ralf Baechle</name>
<email>ralf@linux-mips.org</email>
</author>
<published>2013-02-21T15:16:55+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=edb15d83a875a1f4b1576188844db5c330c3267d'/>
<id>edb15d83a875a1f4b1576188844db5c330c3267d</id>
<content type='text'>
Conflicts:
    include/linux/ssb/ssb_driver_gige.h

Also resolves a logical merge conflict in drivers/net/ethernet/broadcom/-
bgmac.c due to change of an API.
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Conflicts:
    include/linux/ssb/ssb_driver_gige.h

Also resolves a logical merge conflict in drivers/net/ethernet/broadcom/-
bgmac.c due to change of an API.
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'tty-3.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty</title>
<updated>2013-02-21T21:41:04+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2013-02-21T21:41:04+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=21eaab6d19ed43e82ed39c8deb7f192134fb4a0e'/>
<id>21eaab6d19ed43e82ed39c8deb7f192134fb4a0e</id>
<content type='text'>
Pull tty/serial patches from Greg Kroah-Hartman:
 "Here's the big tty/serial driver patches for 3.9-rc1.

  More tty port rework and fixes from Jiri here, as well as lots of
  individual serial driver updates and fixes.

  All of these have been in the linux-next tree for a while."

* tag 'tty-3.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (140 commits)
  tty: mxser: improve error handling in mxser_probe() and mxser_module_init()
  serial: imx: fix uninitialized variable warning
  serial: tegra: assume CONFIG_OF
  TTY: do not update atime/mtime on read/write
  lguest: select CONFIG_TTY to build properly.
  ARM defconfigs: add missing inclusions of linux/platform_device.h
  fb/exynos: include platform_device.h
  ARM: sa1100/assabet: include platform_device.h directly
  serial: imx: Fix recursive locking bug
  pps: Fix build breakage from decoupling pps from tty
  tty: Remove ancient hardpps()
  pps: Additional cleanups in uart_handle_dcd_change
  pps: Move timestamp read into PPS code proper
  pps: Don't crash the machine when exiting will do
  pps: Fix a use-after free bug when unregistering a source.
  pps: Use pps_lookup_dev to reduce ldisc coupling
  pps: Add pps_lookup_dev() function
  tty: serial: uartlite: Support uartlite on big and little endian systems
  tty: serial: uartlite: Fix sparse and checkpatch warnings
  serial/arc-uart: Miscll DT related updates (Grant's review comments)
  ...

Fix up trivial conflicts, mostly just due to the TTY config option
clashing with the EXPERIMENTAL removal.
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull tty/serial patches from Greg Kroah-Hartman:
 "Here's the big tty/serial driver patches for 3.9-rc1.

  More tty port rework and fixes from Jiri here, as well as lots of
  individual serial driver updates and fixes.

  All of these have been in the linux-next tree for a while."

* tag 'tty-3.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (140 commits)
  tty: mxser: improve error handling in mxser_probe() and mxser_module_init()
  serial: imx: fix uninitialized variable warning
  serial: tegra: assume CONFIG_OF
  TTY: do not update atime/mtime on read/write
  lguest: select CONFIG_TTY to build properly.
  ARM defconfigs: add missing inclusions of linux/platform_device.h
  fb/exynos: include platform_device.h
  ARM: sa1100/assabet: include platform_device.h directly
  serial: imx: Fix recursive locking bug
  pps: Fix build breakage from decoupling pps from tty
  tty: Remove ancient hardpps()
  pps: Additional cleanups in uart_handle_dcd_change
  pps: Move timestamp read into PPS code proper
  pps: Don't crash the machine when exiting will do
  pps: Fix a use-after free bug when unregistering a source.
  pps: Use pps_lookup_dev to reduce ldisc coupling
  pps: Add pps_lookup_dev() function
  tty: serial: uartlite: Support uartlite on big and little endian systems
  tty: serial: uartlite: Fix sparse and checkpatch warnings
  serial/arc-uart: Miscll DT related updates (Grant's review comments)
  ...

Fix up trivial conflicts, mostly just due to the TTY config option
clashing with the EXPERIMENTAL removal.
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'driver-core-3.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core</title>
<updated>2013-02-21T20:05:51+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2013-02-21T20:05:51+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=06991c28f37ad68e5c03777f5c3b679b56e3dac1'/>
<id>06991c28f37ad68e5c03777f5c3b679b56e3dac1</id>
<content type='text'>
Pull driver core patches from Greg Kroah-Hartman:
 "Here is the big driver core merge for 3.9-rc1

  There are two major series here, both of which touch lots of drivers
  all over the kernel, and will cause you some merge conflicts:

   - add a new function called devm_ioremap_resource() to properly be
     able to check return values.

   - remove CONFIG_EXPERIMENTAL

  Other than those patches, there's not much here, some minor fixes and
  updates"

Fix up trivial conflicts

* tag 'driver-core-3.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (221 commits)
  base: memory: fix soft/hard_offline_page permissions
  drivercore: Fix ordering between deferred_probe and exiting initcalls
  backlight: fix class_find_device() arguments
  TTY: mark tty_get_device call with the proper const values
  driver-core: constify data for class_find_device()
  firmware: Ignore abort check when no user-helper is used
  firmware: Reduce ifdef CONFIG_FW_LOADER_USER_HELPER
  firmware: Make user-mode helper optional
  firmware: Refactoring for splitting user-mode helper code
  Driver core: treat unregistered bus_types as having no devices
  watchdog: Convert to devm_ioremap_resource()
  thermal: Convert to devm_ioremap_resource()
  spi: Convert to devm_ioremap_resource()
  power: Convert to devm_ioremap_resource()
  mtd: Convert to devm_ioremap_resource()
  mmc: Convert to devm_ioremap_resource()
  mfd: Convert to devm_ioremap_resource()
  media: Convert to devm_ioremap_resource()
  iommu: Convert to devm_ioremap_resource()
  drm: Convert to devm_ioremap_resource()
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull driver core patches from Greg Kroah-Hartman:
 "Here is the big driver core merge for 3.9-rc1

  There are two major series here, both of which touch lots of drivers
  all over the kernel, and will cause you some merge conflicts:

   - add a new function called devm_ioremap_resource() to properly be
     able to check return values.

   - remove CONFIG_EXPERIMENTAL

  Other than those patches, there's not much here, some minor fixes and
  updates"

Fix up trivial conflicts

* tag 'driver-core-3.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (221 commits)
  base: memory: fix soft/hard_offline_page permissions
  drivercore: Fix ordering between deferred_probe and exiting initcalls
  backlight: fix class_find_device() arguments
  TTY: mark tty_get_device call with the proper const values
  driver-core: constify data for class_find_device()
  firmware: Ignore abort check when no user-helper is used
  firmware: Reduce ifdef CONFIG_FW_LOADER_USER_HELPER
  firmware: Make user-mode helper optional
  firmware: Refactoring for splitting user-mode helper code
  Driver core: treat unregistered bus_types as having no devices
  watchdog: Convert to devm_ioremap_resource()
  thermal: Convert to devm_ioremap_resource()
  spi: Convert to devm_ioremap_resource()
  power: Convert to devm_ioremap_resource()
  mtd: Convert to devm_ioremap_resource()
  mmc: Convert to devm_ioremap_resource()
  mfd: Convert to devm_ioremap_resource()
  media: Convert to devm_ioremap_resource()
  iommu: Convert to devm_ioremap_resource()
  drm: Convert to devm_ioremap_resource()
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'for-3.9-cleanups' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq</title>
<updated>2013-02-20T05:58:52+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2013-02-20T05:58:52+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=1eaec8212e35aef6606a4e8b40aa9ad9ba87672a'/>
<id>1eaec8212e35aef6606a4e8b40aa9ad9ba87672a</id>
<content type='text'>
Pull workqueue [delayed_]work_pending() cleanups from Tejun Heo:
 "This is part of on-going cleanups to remove / minimize usages of
  workqueue interfaces which are deprecated and/or misleading.

  This round drops a number of usages of [delayed_]work_pending(), which
  are dangerous as they lack any form of synchronization and thus often
  lead to buggy / unnecessary code.  There are a couple legitimate use
  cases in kernel.  Hopefully, they can be converted and
  [delayed_]work_pending() can be removed completely.  Even if not,
  removing most of misuses should make it more difficult to find
  examples of misuses and thus slow down growth of them.

  These changes are independent from other workqueue changes."

* 'for-3.9-cleanups' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  wimax/i2400m: fix i2400m-&gt;wake_tx_skb handling
  kprobes: fix wait_for_kprobe_optimizer()
  ipw2x00: simplify scan_event handling
  video/exynos: don't use [delayed_]work_pending()
  tty/max3100: don't use [delayed_]work_pending()
  x86/mce: don't use [delayed_]work_pending()
  rfkill: don't use [delayed_]work_pending()
  wl1251: don't use [delayed_]work_pending()
  thinkpad_acpi: don't use [delayed_]work_pending()
  mwifiex: don't use [delayed_]work_pending()
  sja1000: don't use [delayed_]work_pending()
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull workqueue [delayed_]work_pending() cleanups from Tejun Heo:
 "This is part of on-going cleanups to remove / minimize usages of
  workqueue interfaces which are deprecated and/or misleading.

  This round drops a number of usages of [delayed_]work_pending(), which
  are dangerous as they lack any form of synchronization and thus often
  lead to buggy / unnecessary code.  There are a couple legitimate use
  cases in kernel.  Hopefully, they can be converted and
  [delayed_]work_pending() can be removed completely.  Even if not,
  removing most of misuses should make it more difficult to find
  examples of misuses and thus slow down growth of them.

  These changes are independent from other workqueue changes."

* 'for-3.9-cleanups' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  wimax/i2400m: fix i2400m-&gt;wake_tx_skb handling
  kprobes: fix wait_for_kprobe_optimizer()
  ipw2x00: simplify scan_event handling
  video/exynos: don't use [delayed_]work_pending()
  tty/max3100: don't use [delayed_]work_pending()
  x86/mce: don't use [delayed_]work_pending()
  rfkill: don't use [delayed_]work_pending()
  wl1251: don't use [delayed_]work_pending()
  thinkpad_acpi: don't use [delayed_]work_pending()
  mwifiex: don't use [delayed_]work_pending()
  sja1000: don't use [delayed_]work_pending()
</pre>
</div>
</content>
</entry>
<entry>
<title>serial: imx: fix uninitialized variable warning</title>
<updated>2013-02-18T19:05:14+00:00</updated>
<author>
<name>Shawn Guo</name>
<email>shawn.guo@linaro.org</email>
</author>
<published>2013-02-18T05:15:36+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=f30e826069918da0876493e2de9ba13287b68e0a'/>
<id>f30e826069918da0876493e2de9ba13287b68e0a</id>
<content type='text'>
Commit 677fe55 (serial: imx: Fix recursive locking bug) introduces an
uninitialized variable warning as below.

  CC      drivers/tty/serial/imx.o
drivers/tty/serial/imx.c: In function ‘imx_console_write’:
include/linux/spinlock.h:340:2: warning: ‘flags’ may be used uninitialized in this function [-Wuninitialized]
drivers/tty/serial/imx.c:1214:16: note: ‘flags’ was declared here

Initialize the variable to suppress the warning.

Signed-off-by: Shawn Guo &lt;shawn.guo@linaro.org&gt;
Acked-by: Dirk Behme &lt;dirk.behme@de.bosch.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Commit 677fe55 (serial: imx: Fix recursive locking bug) introduces an
uninitialized variable warning as below.

  CC      drivers/tty/serial/imx.o
drivers/tty/serial/imx.c: In function ‘imx_console_write’:
include/linux/spinlock.h:340:2: warning: ‘flags’ may be used uninitialized in this function [-Wuninitialized]
drivers/tty/serial/imx.c:1214:16: note: ‘flags’ was declared here

Initialize the variable to suppress the warning.

Signed-off-by: Shawn Guo &lt;shawn.guo@linaro.org&gt;
Acked-by: Dirk Behme &lt;dirk.behme@de.bosch.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>serial: tegra: assume CONFIG_OF</title>
<updated>2013-02-15T22:47:04+00:00</updated>
<author>
<name>Stephen Warren</name>
<email>swarren@nvidia.com</email>
</author>
<published>2013-02-15T22:04:45+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=c3e1becebfe115f827ea2242218c9a8f627c094f'/>
<id>c3e1becebfe115f827ea2242218c9a8f627c094f</id>
<content type='text'>
Tegra only supports, and always enables, device tree. Remove all ifdefs
for DT support from the driver.

Signed-off-by: Stephen Warren &lt;swarren@nvidia.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Tegra only supports, and always enables, device tree. Remove all ifdefs
for DT support from the driver.

Signed-off-by: Stephen Warren &lt;swarren@nvidia.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>serial: imx: Fix recursive locking bug</title>
<updated>2013-02-14T20:17:20+00:00</updated>
<author>
<name>Thomas Gleixner</name>
<email>tglx@linutronix.de</email>
</author>
<published>2013-02-14T20:01:06+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=677fe555cbfb188af58cce105f4dae9505e58c31'/>
<id>677fe555cbfb188af58cce105f4dae9505e58c31</id>
<content type='text'>
commit 9ec1882df2 (tty: serial: imx: console write routing is unsafe
on SMP) introduced a recursive locking bug in imx_console_write().

The callchain is:

imx_rxint()
  spin_lock_irqsave(&amp;sport-&gt;port.lock,flags);
  ...
  uart_handle_sysrq_char();
    sysrq_function();
      printk();
        imx_console_write();
          spin_lock_irqsave(&amp;sport-&gt;port.lock,flags); &lt;--- DEAD

The bad news is that the kernel debugging facilities can dectect the
problem, but the printks never surface on the serial console for
obvious reasons.

There is a similar issue with oops_in_progress. If the kernel crashes
we really don't want to be stuck on the lock and unable to tell what
happened.

In general most UP originated drivers miss these checks and nobody
ever notices because CONFIG_PROVE_LOCKING seems to be still ignored by
a large number of developers.

The solution is to avoid locking in the sysrq case and trylock in the
oops_in_progress case.

This scheme is used in other drivers as well and it would be nice if
we could move this to a common place, so the usual copy/paste/modify
bugs can be avoided.

Now there is another issue with this scheme:

CPU0 	    	     	 CPU1
printk()
			 rxint()
			   sysrq_detection() -&gt; sets port-&gt;sysrq
			 return from interrupt
  console_write()
     if (port-&gt;sysrq)
     	avoid locking

port-&gt;sysrq is reset with the next receive character. So as long as
the port-&gt;sysrq is not reset and this can take an endless amount of
time if after the break no futher receive character follows, all
console writes happen unlocked.

While the current writer is protected against other console writers by
the console sem, it's unprotected against open/close or other
operations which fiddle with the port. That's what the above mentioned
commit tried to solve.

That's an issue in all drivers which use that scheme and unfortunately
there is no easy workaround. The only solution is to have a separate
indicator port-&gt;sysrq_cpu. uart_handle_sysrq_char() then sets it to
smp_processor_id() before calling into handle_sysrq() and resets it to
-1 after that. Then change the locking check to:

     if (port-&gt;sysrq_cpu == smp_processor_id())
     	 locked = 0;
     else if (oops_in_progress)
         locked = spin_trylock_irqsave(port-&gt;lock, flags);
     else
  	 spin_lock_irqsave(port-&gt;lock, flags);

That would force all other cpus into the spin_lock path. Problem
solved, but that's way beyond the scope of this fix and really wants
to be implemented in a common function which calls the uart specific
write function to avoid another gazillion of hard to debug
copy/paste/modify bugs.

Reported-and-tested-by: Tim Sander &lt;tim@krieglstein.org&gt;
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: stable &lt;stable@vger.kernel.org&gt;  # 3.6+
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
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<pre>
commit 9ec1882df2 (tty: serial: imx: console write routing is unsafe
on SMP) introduced a recursive locking bug in imx_console_write().

The callchain is:

imx_rxint()
  spin_lock_irqsave(&amp;sport-&gt;port.lock,flags);
  ...
  uart_handle_sysrq_char();
    sysrq_function();
      printk();
        imx_console_write();
          spin_lock_irqsave(&amp;sport-&gt;port.lock,flags); &lt;--- DEAD

The bad news is that the kernel debugging facilities can dectect the
problem, but the printks never surface on the serial console for
obvious reasons.

There is a similar issue with oops_in_progress. If the kernel crashes
we really don't want to be stuck on the lock and unable to tell what
happened.

In general most UP originated drivers miss these checks and nobody
ever notices because CONFIG_PROVE_LOCKING seems to be still ignored by
a large number of developers.

The solution is to avoid locking in the sysrq case and trylock in the
oops_in_progress case.

This scheme is used in other drivers as well and it would be nice if
we could move this to a common place, so the usual copy/paste/modify
bugs can be avoided.

Now there is another issue with this scheme:

CPU0 	    	     	 CPU1
printk()
			 rxint()
			   sysrq_detection() -&gt; sets port-&gt;sysrq
			 return from interrupt
  console_write()
     if (port-&gt;sysrq)
     	avoid locking

port-&gt;sysrq is reset with the next receive character. So as long as
the port-&gt;sysrq is not reset and this can take an endless amount of
time if after the break no futher receive character follows, all
console writes happen unlocked.

While the current writer is protected against other console writers by
the console sem, it's unprotected against open/close or other
operations which fiddle with the port. That's what the above mentioned
commit tried to solve.

That's an issue in all drivers which use that scheme and unfortunately
there is no easy workaround. The only solution is to have a separate
indicator port-&gt;sysrq_cpu. uart_handle_sysrq_char() then sets it to
smp_processor_id() before calling into handle_sysrq() and resets it to
-1 after that. Then change the locking check to:

     if (port-&gt;sysrq_cpu == smp_processor_id())
     	 locked = 0;
     else if (oops_in_progress)
         locked = spin_trylock_irqsave(port-&gt;lock, flags);
     else
  	 spin_lock_irqsave(port-&gt;lock, flags);

That would force all other cpus into the spin_lock path. Problem
solved, but that's way beyond the scope of this fix and really wants
to be implemented in a common function which calls the uart specific
write function to avoid another gazillion of hard to debug
copy/paste/modify bugs.

Reported-and-tested-by: Tim Sander &lt;tim@krieglstein.org&gt;
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: stable &lt;stable@vger.kernel.org&gt;  # 3.6+
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
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</entry>
<entry>
<title>tty: Remove ancient hardpps()</title>
<updated>2013-02-13T18:17:06+00:00</updated>
<author>
<name>Peter Hurley</name>
<email>peter@hurleysoftware.com</email>
</author>
<published>2013-02-06T15:55:16+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=bc80fbe46be7430487a45ad92841932bb2eaa3e6'/>
<id>bc80fbe46be7430487a45ad92841932bb2eaa3e6</id>
<content type='text'>
hardpps() functionality is provided through the N_PPS line
discipline now. The new function signature was added in commit
025b40ab (2011-01-12). There was no previous macro or
function hardpps(), at least since before the initial commit of
v2.6.12 in 2005. It's unlikely this code has been compiled since.

Signed-off-by: Peter Hurley &lt;peter@hurleysoftware.com&gt;
Signed-off-by: George Spelvin &lt;linux@horizon.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
hardpps() functionality is provided through the N_PPS line
discipline now. The new function signature was added in commit
025b40ab (2011-01-12). There was no previous macro or
function hardpps(), at least since before the initial commit of
v2.6.12 in 2005. It's unlikely this code has been compiled since.

Signed-off-by: Peter Hurley &lt;peter@hurleysoftware.com&gt;
Signed-off-by: George Spelvin &lt;linux@horizon.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>pps: Additional cleanups in uart_handle_dcd_change</title>
<updated>2013-02-13T18:17:06+00:00</updated>
<author>
<name>George Spelvin</name>
<email>linux@horizon.com</email>
</author>
<published>2013-02-10T09:44:30+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=42381572f586d4da57e7d65e0fcb45422be3ba7b'/>
<id>42381572f586d4da57e7d65e0fcb45422be3ba7b</id>
<content type='text'>
An extension of the previous commit, there is no semantic change
here, just fewer lines of source code.

Signed-off-by: George Spelvin &lt;linux@horizon.com&gt;
Acked-by: Rodolfo Giometti &lt;giometti@enneenne.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
An extension of the previous commit, there is no semantic change
here, just fewer lines of source code.

Signed-off-by: George Spelvin &lt;linux@horizon.com&gt;
Acked-by: Rodolfo Giometti &lt;giometti@enneenne.com&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
</feed>
