kernel.git/arch/s390/kernel, branch linux-2.6.37.y

s390: remove task_show_regs

2011-02-24T22:54:30Z

commit 261cd298a8c363d7985e3482946edb4bfedacf98 upstream. task_show_regs used to be a debugging aid in the early bringup days of Linux on s390. /proc//status is a world readable file, it is not a good idea to show the registers of a process. The only correct fix is to remove task_show_regs. Reported-by: Al Viro Signed-off-by: Martin Schwidefsky Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

[S390] nohz/s390: fix arch_needs_cpu() return value on offline cpus

2010-12-01T09:08:17Z

This fixes the same problem as described in the patch "nohz: fix printk_needs_cpu() return value on offline cpus" for the arch_needs_cpu() primitive: arch_needs_cpu() may return 1 if called on offline cpus. When a cpu gets offlined it schedules the idle process which, before killing its own cpu, will call tick_nohz_stop_sched_tick(). That function in turn will call arch_needs_cpu() in order to check if the local tick can be disabled. On offline cpus this function should naturally return 0 since regardless if the tick gets disabled or not the cpu will be dead short after. That is besides the fact that __cpu_disable() should already have made sure that no interrupts on the offlined cpu will be delivered anyway. In this case it prevents tick_nohz_stop_sched_tick() to call select_nohz_load_balancer(). No idea if that really is a problem. However what made me debug this is that on 2.6.32 the function get_nohz_load_balancer() is used within __mod_timer() to select a cpu on which a timer gets enqueued. If arch_needs_cpu() returns 1 then the nohz_load_balancer cpu doesn't get updated when a cpu gets offlined. It may contain the cpu number of an offline cpu. In turn timers get enqueued on an offline cpu and not very surprisingly they never expire and cause system hangs. This has been observed 2.6.32 kernels. On current kernels __mod_timer() uses get_nohz_timer_target() which doesn't have that problem. However there might be other problems because of the too early exit tick_nohz_stop_sched_tick() in case a cpu goes offline. This specific bug was indrocuded with 3c5d92a0 "nohz: Introduce arch_needs_cpu". In this case a cpu hotplug notifier is used to fix the issue in order to keep the normal/fast path small. All we need to do is to clear the condition that makes arch_needs_cpu() return 1 since it is just a performance improvement which is supposed to keep the local tick running for a short period if a cpu goes idle. Nothing special needs to be done except for clearing the condition. Cc: stable@kernel.org Acked-by: Peter Zijlstra Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

[S390] nmi: fix clock comparator revalidation

2010-11-25T08:52:59Z

On each machine check all registers are revalidated. The save area for the clock comparator however only contains the upper most seven bytes of the former contents, if valid. Therefore the machine check handler uses a store clock instruction to get the current time and writes that to the clock comparator register which in turn will generate an immediate timer interrupt. However within the lowcore the expected time of the next timer interrupt is stored. If the interrupt happens before that time the handler won't be called. In turn the clock comparator won't be reprogrammed and therefore the interrupt condition stays pending which causes an interrupt loop until the expected time is reached. On NOHZ machines this can result in unresponsive machines since the time of the next expected interrupted can be a couple of days in the future. To fix this just revalidate the clock comparator register with the expected value. In addition the special handling for udelay must be changed as well. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

BKL: remove extraneous #include

2010-11-17T16:59:32Z

The big kernel lock has been removed from all these files at some point, leaving only the #include. Remove this too as a cleanup. Signed-off-by: Arnd Bergmann Signed-off-by: Linus Torvalds

[S390] kprobes: Fix the return address of multiple kretprobes

2010-11-10T09:05:54Z

Analog to git commit 737480a0d525dae13306296da08029dff545bc72 fix the return address of subsequent kretprobes when multiple kretprobes are set on the same function. Signed-off-by: Martin Schwidefsky

[S390] kprobes: disable interrupts throughout

2010-11-10T09:05:54Z

Execute the kprobe exception and fault handler with interrupts disabled. To disable the interrupts only while a single step is in progress is not good enough, a kprobe from interrupt context while another kprobe is handled can confuse the internal house keeping. Signed-off-by: Martin Schwidefsky

[S390] fix kprobes single stepping

2010-10-29T14:50:50Z

Fix kprobes after git commit 1e54622e0403891b10f2105663e0f9dd595a1f17 broke it. The kprobe_handler is now called with interrupts in the state at the time of the breakpoint. The single step of the replaced instruction is done with interrupts off which makes it necessary to enable and disable the interupts in the kprobes code. Signed-off-by: Martin Schwidefsky

[S390] vdso: get rid of redefinition warnings

2010-10-29T14:50:50Z

The CLOCK_* defines in asm-offsets.c are only used for the vdso code however in the meantime they cause other trouble. Just rename them to get permanently rid of this: In file included from /home2/heicarst/linux-2.6/arch/s390/include/asm/asm-offsets.h:1:0, from arch/s390/mm/fault.c:33: include/generated/asm-offsets.h:53:0: warning: "CLOCK_REALTIME" redefined include/linux/time.h:286:0: note: this is the location of the previous definition include/generated/asm-offsets.h:54:0: warning: "CLOCK_MONOTONIC" redefined include/linux/time.h:287:0: note: this is the location of the previous definition Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

[S390] facility detection: remove unused variable

2010-10-29T14:50:50Z

arch/s390/kernel/early.c: In function 'setup_hpage': arch/s390/kernel/early.c:285:15: warning: unused variable 'facilities' Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

[S390] topology: fix cpu masks for topology=off case

2010-10-29T14:50:50Z

Fix cpu masks for 'topology=off' case. Folding of the scheduling domains happen in such a way that everything belongs to the MC domain instead of the CPU doimain. This should fix a performance regression introduced with eafd2b6d "[S390] topology: use default MC domain initializer" and also makes sure we have the same behavious as if CONFIG_SCHED_MC was not selected at all. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky