Paul Mackerras [Sat, 27 Aug 2005 23:40:01 +0000 (09:40 +1000)]
[PATCH] Remove race between con_open and con_close
[ Same race and same patch also by Steven Rostedt <rostedt@goodmis.org> ]
I have a laptop (G3 powerbook) which will pretty reliably hit a race
between con_open and con_close late in the boot process and oops in
vt_ioctl due to tty->driver_data being NULL.
What happens is this: process A opens /dev/tty6; it comes into
con_open() (drivers/char/vt.c) and assign a non-NULL value to
tty->driver_data. Then process A closes that and concurrently process
B opens /dev/tty6. Process A gets through con_close() and clears
tty->driver_data, since tty->count == 1. However, before process A
can decrement tty->count, we switch to process B (e.g. at the
down(&tty_sem) call at drivers/char/tty_io.c line 1626).
So process B gets to run and comes into con_open with tty->count == 2,
as tty->count is incremented (in init_dev) before con_open is called.
Because tty->count != 1, we don't set tty->driver_data. Then when the
process tries to do anything with that fd, it oopses.
The simple and effective fix for this is to test tty->driver_data
rather than tty->count in con_open. The testing and setting of
tty->driver_data is serialized with respect to the clearing of
tty->driver_data in con_close by the console_sem. We can't get a
situation where con_open sees tty->driver_data != NULL and then
con_close on a different fd clears tty->driver_data, because
tty->count is incremented before con_open is called. Thus this patch
eliminates the race, and in fact with this patch my laptop doesn't
oops.
Signed-off-by: Paul Mackerras <paulus@samba.org>
[ Same patch Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
in http://marc.theaimsgroup.com/?l=linux-kernel&m=112450820432121&w=2 ] Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Jan Blunck [Sat, 27 Aug 2005 18:07:52 +0000 (11:07 -0700)]
[PATCH] sg.c: fix a memory leak in devices seq_file implementation
I know that scsi procfs is legacy code but this is a fix for a memory leak.
While reading through sg.c I realized that the implementation of
/proc/scsi/sg/devices with seq_file is leaking memory due to freeing the
pointer returned by the next() iterator method. Since next() might return
NULL or an error this is wrong. This patch fixes it through using the
seq_files private field for holding the reference to the iterator object.
Here is a small bash script to trigger the leak. Use slabtop to watch
the size-32 usage grow and grow.
#!/bin/sh
while true; do
cat /proc/scsi/sg/devices > /dev/null
done
Signed-off-by: Jan Blunck <j.blunck@tu-harburg.de> Acked-by: James Bottomley <James.Bottomley@steeleye.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
[PATCH] fix for race problem in DVB USB drivers (dibusb)
Fixed race between submitting streaming URBs in the driver and starting
the actual transfer in hardware (demodulator and USB controller) which
sometimes lead to garbled data transfers. URBs are now submitted first,
then the transfer is enabled. Dibusb devices and clones are now fully
functional again.
Signed-off-by: Patrick Boettcher <pb@linuxtv.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Ralf Baechle [Wed, 24 Aug 2005 17:01:33 +0000 (18:01 +0100)]
[PATCH] Fix 6pack setting of MAC address
Don't check type of sax25_family; dev_set_mac_address has already done
that before and anyway, the type to check against would have been
ARPHRD_AX25. We only got away because AF_AX25 and ARPHRD_AX25 both happen
to be defined to the same value.
Don't check sax25_ndigis either; it's value is insignificant for the
purpose of setting the MAC address and the check has shown to break
some application software for no good reason.
Signed-off-by: Ralf Baechle DL5RB <ralf@linux-mips.org> Signed-off-by: Jeff Garzik <jgarzik@pobox.com>
James Bottomley [Sat, 27 Aug 2005 01:34:17 +0000 (18:34 -0700)]
[PATCH] Fix oops in sysfs_hash_and_remove_file()
The problem arises if an entity in sysfs is created and removed without
ever having been made completely visible. In SCSI this is triggered by
removing a device while it's initialising.
The problem appears to be that because it was never made visible in sysfs,
the sysfs dentry has a null d_inode which oopses when a reference is made
to it. The solution is simply to check d_inode and assume the object was
never made visible (and thus doesn't need deleting) if it's NULL.
(akpm: possibly a stopgap for 2.6.13 scsi problems. May not be the
long-term fix)
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com> Cc: Greg KH <greg@kroah.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Deepak Saxena [Sat, 27 Aug 2005 01:34:11 +0000 (18:34 -0700)]
[PATCH] arm: fix IXP4xx flash resource range
We are currently reserving one byte more than actually needed by the flash
device and overlapping into the next I/O expansion bus window. This a)
causes us to allocate an extra page of VM due to ARM ioremap() alignment
code and b) could cause problems if another driver tries to request the
next expansion bus window.
Signed-off-by: Deepak Saxena <dsaxena@plexity.net> Cc: Russell King <rmk@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Andi Kleen [Sat, 27 Aug 2005 01:34:10 +0000 (18:34 -0700)]
[PATCH] x86_64: Tell VM about holes in nodes
Some nodes can have large holes on x86-64.
This fixes problems with the VM allowing too many dirty pages because it
overestimates the number of available RAM in a node. In extreme cases you
can end up with all RAM filled with dirty pages which can lead to deadlocks
and other nasty behaviour.
This patch just tells the VM about the known holes from e820. Reserved
(like the kernel text or mem_map) is still not taken into account, but that
should be only a few percent error now.
Small detail is that the flat setup uses the NUMA free_area_init_node() now
too because it offers more flexibility.
(akpm: lotsa thanks to Martin for working this problem out)
Cc: Martin Bligh <mbligh@mbligh.org> Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Anton Blanchard [Sat, 27 Aug 2005 01:34:07 +0000 (18:34 -0700)]
[PATCH] ppc64: Fix issue with gcc 4.0 compiled kernels
I recently had a BUG_ON() go off spuriously on a gcc 4.0 compiled kernel.
It turns out gcc-4.0 was removing a sign extension while earlier gcc
versions would not. Thinking this to be a compiler bug, I submitted a
report:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23422
It turns out we need to cast the input in order to tell gcc to sign extend
it.
Thanks to Andrew Pinski for his help on this bug.
Signed-off-by: Anton Blanchard <anton@samba.org> Cc: Paul Mackerras <paulus@samba.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
At the suggestion of Nick Piggin and Dinakar, totally disable
the facility to allow cpu_exclusive cpusets to define dynamic
sched domains in Linux 2.6.13, in order to avoid problems
first reported by John Hawkes (corrupt sched data structures
and kernel oops).
This has been built for ppc64, i386, ia64, x86_64, sparc, alpha.
It has been built, booted and tested for cpuset functionality
on an SN2 (ia64).
Dinakar or Nick - could you verify that it for sure does avoid
the problems Hawkes reported. Hawkes is out of town, and I don't
have the recipe to reproduce what he found.
Signed-off-by: Paul Jackson <pj@sgi.com> Acked-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The partial disabling of Dinakar's new facility to allow
cpu_exclusive cpusets to define dynamic sched domains
doesn't go far enough. At the suggestion of Nick Piggin
and Dinakar, let us instead totally disable this facility
for 2.6.13, in order to avoid problems first reported
by John Hawkes (corrupt sched data structures and kernel oops).
This patch removes the partial disabling code in 2.6.13-rc7,
in anticipation of the next patch, which will totally disable
it instead.
Signed-off-by: Paul Jackson <pj@sgi.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Jean Delvare [Thu, 25 Aug 2005 16:43:37 +0000 (18:43 +0200)]
[PATCH] hwmon: Off-by-one error in fscpos driver
Coverity uncovered an off-by-one error in the fscpos driver, in function
set_temp_reset(). Writing to the temp3_reset sysfs file will lead to an
array overrun, in turn causing an I2C write to a random register of the
FSC Poseidon chip. Additionally, writing to temp1_reset and temp2_reset
will not work as expected. The fix is straightforward.
Signed-off-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Al Viro [Thu, 25 Aug 2005 22:13:14 +0000 (23:13 +0100)]
[PATCH] late spinlock initialization in ieee1394/ohci
spinlock used in irq handler should be initialized before registering
irq, even if we know that our device has interrupts disabled; handler
is registered shared and taking spinlock is done unconditionally. As
it is, we can and do get oopsen on boot for some configuration, depending
on irq routing - I've got a reproducer.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk> Signed-off-by: Ben Collins <bcollins@debian.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Al Viro [Thu, 25 Aug 2005 22:03:35 +0000 (23:03 +0100)]
[PATCH] bogus function type in qdio
In qdio_get_micros() volatile in return type is plain noise (even with old
gccisms it would make no sense - noreturn function returning __u64 is a
bit odd ;-)
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Alexey Dobriyan [Thu, 25 Aug 2005 21:49:14 +0000 (01:49 +0400)]
[PATCH] drivers/hwmon/*: kfree() correct pointers
The adm9240 driver, in adm9240_detect(), allocates a structure. The
error path attempts to kfree() ->client field of it (second one),
resulting in an oops (or slab corruption) if the hardware is not present.
->client field in adm1026, adm1031, smsc47b397 and smsc47m1 is the first in
${HWMON}_data structure, but fix them too.
Steve French [Fri, 26 Aug 2005 19:42:59 +0000 (14:42 -0500)]
[PATCH] Fix oops in fs/locks.c on close of file with pending locks
The recent change to locks_remove_flock code in fs/locks.c changes how
byte range locks are removed from closing files, which shows up a bug in
cifs.
The assumption in the cifs code was that the close call sent to the
server would remove any pending locks on the server on this file, but
that is no longer safe as the fs/locks.c code on the client wants unlock
of 0 to PATH_MAX to remove all locks (at least from this client, it is
not possible AFAIK to remove all locks from other clients made to the
server copy of the file).
Note that cifs locks are different from posix locks - and it is not
possible to map posix locks perfectly on the wire yet, due to
restrictions of the cifs network protocol, even to Samba without adding
a new request type to the network protocol (which we plan to do for
Samba 3.0.21 within a few months), but the local client will have the
correct, posix view, of the lock in most cases.
The correct fix for cifs for this would involve a bigger change than I
would like to do this late in the 2.6.13-rc cycle - and would involve
cifs keeping track of all unmerged (uncoalesced) byte range locks for
each remote inode and scanning that list to remove locks that intersect
or fall wholly within the range - locks that intersect may have to be
reaquired with the smaller, remaining range.
Signed-off-by: Steve French <sfrench@us.ibm.com> Signed-off-by: Dave Kleikamp <shaggy@austin.ibm.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
There is an off by one problem with idr_get_new_above.
The comment and function name suggest that it will return an id >
starting_id, but it actually returned an id >= starting_id, and kernel
callers other than inotify treated it as such.
The patch below fixes the comment, and fixes inotifys usage. The
function name still doesn't match the behaviour, but it never did.
Signed-off-by: John McCutchan <ttb@tentacle.dhs.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Linus Torvalds [Fri, 26 Aug 2005 17:49:22 +0000 (10:49 -0700)]
Ignore disabled ROM resources at setup
Writing even a disabled value seems to mess up some matrox graphics
cards. It may be a card-related issue, but we may also be writing
reserved low bits in the result.
This was a fall-out of switching x86 over to the generic PCI resource
allocation code, and needs more debugging. In particular, the old x86
code defaulted to not doing any resource allocations at all for ROM
resources.
In the meantime, this has been reported to make X happier by Helge
Hafting <helgehaf@aitel.hist.no>.
Linus Torvalds [Fri, 26 Aug 2005 17:40:10 +0000 (10:40 -0700)]
Only pre-allocate 256 bytes of cardbio IO range
It may seem small, but most cards need much less, if any, and this not
only makes the code adhere to the comment, it seems to fix a boot-time
lockup on a ThinkPad 380XD laptop reported by Tero Roponen <teanropo@cc.jyu.fi>
Michael Chan [Thu, 25 Aug 2005 22:31:41 +0000 (15:31 -0700)]
[TG3]: Fix ethtool loopback test lockup
The tg3_abort_hw() call in tg3_test_loopback() is causing lockups on
some devices. tg3_abort_hw() disables the memory arbiter, causing
tg3_reset_hw() to hang when it tries to write the pre-reset signature.
tg3_abort_hw() should only be called after the pre-reset signature has
been written. This is all done in tg3_reset_hw() so the tg3_abort_hw()
call is unnecessary and can be removed.
[ Also bump driver version and release date. -DaveM ]
Signed-off-by: Michael Chan <mchan@broadcom.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Jens Axboe [Wed, 24 Aug 2005 12:57:54 +0000 (14:57 +0200)]
[PATCH] cfq-iosched.c: minor fixes
One critical fix and two minor fixes for 2.6.13-rc7:
- Max depth must currently be 2 to allow barriers to function on SCSI
- Prefer sync request over async in choosing the next request
- Never allow async request to preempt or disturb the "anticipation" for
a single cfq process context. This is as-designed, the code right now
is buggy in that area.
Keith Owens [Wed, 24 Aug 2005 06:06:25 +0000 (16:06 +1000)]
[PATCH] Export pcibios_bus_to_resource
pcibios_bus_to_resource is exported on all architectures except ia64
and sparc. Add exports for the two missing architectures. Needed when
Yenta socket support is compiled as a module.
Signed-off-by: Keith Owens <kaos@sgi.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
I mistakedly disabled fusion support in an earlier update. Fusion
is commonly used on many x86-64 systems, so this was a problem.
This patch fixes that.
Signed-off-by: And Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
[PATCH] ppc64: Export machine_power_off for therm_pm72 module
This patch puts back the export of machine_power_off() that was removed
by some janitor as it's used for emergency shutdown by the G5 thermal
control driver. Wether that driver should use kernel_power_off() instead
is debatable and a post-2.6.13 decision. In the meantime, please commit
that patch that fixes the driver for now.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Paul Jackson [Wed, 24 Aug 2005 11:15:10 +0000 (04:15 -0700)]
[PATCH] cpu_exclusive sched domains build fix
As reported by Paul Mackerras <paulus@samba.org>, the previous patch
"cpu_exclusive sched domains fix" broke the ppc64 build with
CONFIC_CPUSET, yielding error messages:
kernel/cpuset.c: In function 'update_cpu_domains':
kernel/cpuset.c:648: error: invalid lvalue in unary '&'
kernel/cpuset.c:648: error: invalid lvalue in unary '&'
On some arch's, the node_to_cpumask() is a function, returning
a cpumask_t. But the for_each_cpu_mask() requires an lvalue mask.
The following patch fixes this build failure by making a copy
of the cpumask_t on the stack.
Signed-off-by: Paul Jackson <pj@sgi.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Patrick McHardy [Wed, 24 Aug 2005 05:06:09 +0000 (22:06 -0700)]
[FIB_TRIE]: Don't ignore negative results from fib_semantic_match
When a semantic match occurs either success, not found or an error
(for matching unreachable routes/blackholes) is returned. fib_trie
ignores the errors and looks for a different matching route. Treat
results other than "no match" as success and end lookup.
Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Paul Jackson [Tue, 23 Aug 2005 08:04:27 +0000 (01:04 -0700)]
[PATCH] cpu_exclusive sched domains on partial nodes temp fix
This keeps the kernel/cpuset.c routine update_cpu_domains() from
invoking the sched.c routine partition_sched_domains() if the cpuset in
question doesn't fall on node boundaries.
I have boot tested this on an SN2, and with the help of a couple of ad
hoc printk's, determined that it does indeed avoid calling the
partition_sched_domains() routine on partial nodes.
I did not directly verify that this avoids setting up bogus sched
domains or avoids the oops that Hawkes saw.
This patch imposes a silent artificial constraint on which cpusets can
be used to define dynamic sched domains.
This patch should allow proceeding with this new feature in 2.6.13 for
the configurations in which it is useful (node alligned sched domains)
while avoiding trying to setup sched domains in the less useful cases
that can cause the kernel corruption and oops.
Signed-off-by: Paul Jackson <pj@sgi.com> Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: Dinakar Guniguntala <dino@in.ibm.com> Acked-by: John Hawkes <hawkes@sgi.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Andi Kleen [Tue, 23 Aug 2005 01:14:27 +0000 (03:14 +0200)]
[PATCH] x86_64: Don't oops at boot when empty Opteron node has IO
The code to detect IO links on Opteron would not check
if the node had actually memory. This could lead to pci_bus_to_node
returning an invalid node, which might cause crashes later
when dma_alloc_coherent passes it to page_alloc_node().
The bug has been there forever but for some reason
it is causing now crashes.
lepton [Tue, 23 Aug 2005 00:06:14 +0000 (17:06 -0700)]
[PATCH] usbnet oops fix
There's a "return the wrong SKB" error in the GL620A cable minidriver
(for "usbnet") which can oops. This would not appear when talking
Linux-to-Linux, only Linux-to-Windows (for recent Linuxes).
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Chuck Ebbert [Wed, 24 Aug 2005 01:36:40 +0000 (21:36 -0400)]
[PATCH] i386: fix incorrect FP signal code
i386 floating-point exception handling has a bug that can cause error
code 0 to be sent instead of the proper code during signal delivery.
This is caused by unconditionally checking the IS and c1 bits from the
FPU status word when they are not always relevant. The IS bit tells
whether an exception is a stack fault and is only relevant when the
exception is IE (invalid operation.) The C1 bit determines whether a
stack fault is overflow or underflow and is only relevant when IS and IE
are set.
Al Viro [Tue, 23 Aug 2005 21:47:32 +0000 (22:47 +0100)]
[PATCH] broken inline asm on s390 (misuse of labels)
use of explicit labels in inline asm is a Bad Idea(tm), since gcc can
decide to inline the function in several places. Fixed by use of 1f/f:
instead of .Lfitsin/.Lfitsin:
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Al Viro [Tue, 23 Aug 2005 21:47:22 +0000 (22:47 +0100)]
[PATCH] m32r icu_data gcc4 fixes
either icu_data declaration for SMP case should be taken out of m32102.h,
or its declarations for m32700ut and opsput should not be static for SMP.
Patch does the latter - judging by comments in m32102.h it is intended to
be non-static.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Al Viro [Tue, 23 Aug 2005 21:47:12 +0000 (22:47 +0100)]
[PATCH] alpha spinlock code and bogus constraints
"=m" (lock->lock) / "1" (lock->lock) makes gcc4 unhappy; fixed by s/1/m/,
same as in case of i386 rwsem.h where such variant had been accepted
by both Linus and rth.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Al Viro [Tue, 23 Aug 2005 21:47:07 +0000 (22:47 +0100)]
[PATCH] alpha xchg fix
alpha xchg has to be a macro - alpha disables always_inline and if that
puppy does not get inlined, we immediately blow up on undefined reference.
Happens even on gcc3; with gcc4 that happens a _lot_.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
since sparc32 Kconfig includes drivers/char/Kconfig (instead of duplicating
its parts) we need several new dependencies there to exclude the stuff
broken on sparc32 and not excluded by existing dependencies.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Al Viro [Tue, 23 Aug 2005 21:45:56 +0000 (22:45 +0100)]
[PATCH] Kconfig fix (airo_cs on m32r)
airo_cs is broken on m32r; marked as such. [Proper fix would involve
separating PCI-dependent parts and making sure they don't get in the
way _and_ arranging for asm/scatterlist.h getting picked on m32r]
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Al Viro [Tue, 23 Aug 2005 21:45:46 +0000 (22:45 +0100)]
[PATCH] Kconfig fix (arv)
arv uses constants provided only by include/asm-m32r/m32700ut/m32700ut_lan.h
It won't build for any subarchitecture other than M32700UT; marked as such.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Al Viro [Tue, 23 Aug 2005 21:45:36 +0000 (22:45 +0100)]
[PATCH] Kconfig fix (DEBUG_PAGEALLOC on m32r)
DEBUG_PAGEALLOC is broken on m32r - the option had been blindly copied from
i386; kernel_map_pages() had not and that's what is needed for DEBUG_PAGEALLOC
to work (or link, while we are at it).
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
NeilBrown [Mon, 22 Aug 2005 20:11:08 +0000 (13:11 -0700)]
[PATCH] md: make sure resync gets started when array starts.
We weren't actually waking up the md thread after setting
MD_RECOVERY_NEEDED when assembling an array, so it is possible to lose a
race and not actually start resync.
So add a call to md_wakeup_thread, and while we are at it, remove all the
"if (mddev->thread)" guards as md_wake_thread does its own checking.
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
David Meybohm [Mon, 22 Aug 2005 20:11:08 +0000 (13:11 -0700)]
[PATCH] preempt race in getppid
With CONFIG_PREEMPT && !CONFIG_SMP, it's possible for sys_getppid to
return a bogus value if the parent's task_struct gets reallocated after
current->group_leader->real_parent is read:
asmlinkage long sys_getppid(void)
{
int pid;
struct task_struct *me = current;
struct task_struct *parent;
parent = me->group_leader->real_parent;
RACE HERE => for (;;) {
pid = parent->tgid;
#ifdef CONFIG_SMP
{
struct task_struct *old = parent;
/*
* Make sure we read the pid before re-reading the
* parent pointer:
*/
smp_rmb();
parent = me->group_leader->real_parent;
if (old != parent)
continue;
}
#endif
break;
}
return pid;
}
If the process gets preempted at the indicated point, the parent process
can go ahead and call exit() and then get wait()'d on to reap its
task_struct. When the preempted process gets resumed, it will not do any
further checks of the parent pointer on !CONFIG_SMP: it will read the
bad pid and return.
So, the same algorithm used when SMP is enabled should be used when
preempt is enabled, which will recheck ->real_parent in this case.
Signed-off-by: David Meybohm <dmeybohmlkml@bellsouth.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>