linux-stable.git/arch/mips/kernel/entry.S, branch v3.7

MIPS: Fix endless loop when processing signals for kernel tasks

2012-12-05T18:59:00+00:00

The problem occurs [1] when a kernel-mode task returns from a system
call with a pending signal.

A real-life scenario is a child of 'khelper' returning from a failed
kernel_execve() in ____call_usermodehelper() [ kernel/kmod.c ].
kernel_execve() fails due to a pending SIGKILL, which is the result of
"kill -9 -1" (at least, busybox's init does it upon reboot).

The loop is as follows:

* syscall_exit_work:
 - work_pending:            // start_of_the_loop
 - work_notifysig:
   - do_notify_resume()
     - do_signal()
       - if (!user_mode(regs)) return;
 - resume_userspace         // TIF_SIGPENDING is still set
 - work_pending             // so we call work_pending => goto
                            // start_of_the_loop

More information can be found in another LKML thread:
http://www.serverphorums.com/read.php?12,457826

[1] The problem was also reproduced on !CONFIG_VM86 x86, and the
following fix was accepted.

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=29a2e2836ff9ea65a603c89df217f4198973a74f

Signed-off-by: Dmitry Adamushko 
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3571/
Signed-off-by: Ralf Baechle

MIPS: Merge the identical "return from syscall" per-ABI code

2012-09-22T13:47:31+00:00

No need to keep 4 copies of that stuff; merged and taken to
entry.S, unused public symbols there killed off.

Signed-off-by: Al Viro 
Signed-off-by: Ralf Baechle

MIPS: Prevent hitting do_notify_resume() with !user_mode(regs).

2012-09-22T13:47:11+00:00

Too late to do anything there...

Signed-off-by: Al Viro 
Signed-off-by: Ralf Baechle

MIPS: Split do_syscall_trace into two functions.

2011-05-19T08:55:44+00:00

Signed-off-by: Ralf Baechle

MIPS: Use single define for pending work on syscall exit

2011-05-19T08:55:44+00:00

Signed-off-by: Ralf Baechle

[MIPS] SMTC: Close tiny holes in the SMTC IPI replay system.

2008-10-03T16:58:58+00:00

Signed-off-by: Kevin D. Kissell 
Signed-off-by: Ralf Baechle

[MIPS] SMTC: Interrupt mask backstop hack

2007-07-12T16:41:17+00:00

To support multiple TC microthreads acting as "CPUs" within a VPE,
VPE-wide interrupt mask bits must be specially manipulated during
interrupt handling. To support legacy drivers and interrupt controller
management code, SMTC has a "backstop" to track and if necessary restore
the interrupt mask. This has some performance impact on interrupt service
overhead. Disable it only if you know what you are doing.

Signed-off-by: Ralf Baechle

[MIPS] lockdep: Handle interrupts in R3000 style c0_status register.

2007-03-29T22:46:35+00:00

Check the IEP bit for R3000 style processors when checking to see if
interrupts will be reenabled in restore_all.

Signed-off-by: Chris Dearman 
Signed-off-by: Ralf Baechle

[MIPS] Make entry.S a little more readable.

2007-02-13T22:40:51+00:00

When CONFIG_PREEMPT is not set, it also moves one branch instruction from
ret_from_irq() to ret_from_exception().  Therefore we favour the return
from irq case which should be more common than the other one.

Signed-off-by: Franck Bui-Huu 
Acked-by: Atsushi Nemoto 
Signed-off-by: Ralf Baechle

[MIPS] SMTC: Fix crash if # of TC's > # of VPE's after pt_regs irq cleanup.

2006-11-01T17:46:09+00:00

Signed-off-by: Ralf Baechle