kernel.git/arch/x86_64, branch linux-2.6.19.y

x86_64: fix 2.6.18 regression - PTRACE_OLDSETOPTIONS should be accepted

2007-02-24T00:24:25Z

Also PTRACE_OLDSETOPTIONS should be accepted, as done by kernel/ptrace.c and forced by binary compatibility. UML/32bit breaks because of this - since it is wise enough to use PTRACE_OLDSETOPTIONS to be binary compatible with 2.4 host kernels. Until 2.6.17 (commit f0f2d6536e3515b5b1b7ae97dc8f176860c8c2ce) we had: default: return sys_ptrace(request, pid, addr, data); Instead here we have: case PTRACE_GET_THREAD_AREA: case ...: return sys_ptrace(request, pid, addr, data); default: return -EINVAL; This change was a style change - when a case is added, it must be explicitly tested this way. In this case, not enough testing was done. Cc: Andi Kleen Signed-off-by: Paolo 'Blaisorblade' Giarrusso Signed-off-by: Greg Kroah-Hartman

[PATCH] x86: Work around gcc 4.2 over aggressive optimizer

2007-02-05T16:31:42Z

The new PDA code uses a dummy _proxy_pda variable to describe memory references to the PDA. It is never referenced in inline assembly, but exists as input/output arguments. gcc 4.2 in some cases can CSE references to this which causes unresolved symbols. Define it to zero to avoid this. Signed-off-by: Andi Kleen Signed-off-by: Chris Wright

[PATCH] sched: fix bad missed wakeups in the i386, x86_64, ia64, ACPI and APM idle code

2007-01-10T19:05:19Z

Fernando Lopez-Lezcano reported frequent scheduling latencies and audio xruns starting at the 2.6.18-rt kernel, and those problems persisted all until current -rt kernels. The latencies were serious and unjustified by system load, often in the milliseconds range. After a patient and heroic multi-month effort of Fernando, where he tested dozens of kernels, tried various configs, boot options, test-patches of mine and provided latency traces of those incidents, the following 'smoking gun' trace was captured by him: _------=> CPU# / _-----=> irqs-off | / _----=> need-resched || / _---=> hardirq/softirq ||| / _--=> preempt-depth |||| / ||||| delay cmd pid ||||| time | caller \ / ||||| \ | / IRQ_19-1479 1D..1 0us : __trace_start_sched_wakeup (try_to_wake_up) IRQ_19-1479 1D..1 0us : __trace_start_sched_wakeup <<...>-5856> (37 0) IRQ_19-1479 1D..1 0us : __trace_start_sched_wakeup (c01262ba 0 0) IRQ_19-1479 1D..1 0us : resched_task (try_to_wake_up) IRQ_19-1479 1D..1 0us : __spin_unlock_irqrestore (try_to_wake_up) ... -0 1...1 11us!: default_idle (cpu_idle) ... -0 0Dn.1 602us : smp_apic_timer_interrupt (c0103baf 1 0) ... <...>-5856 0D..2 618us : __switch_to (__schedule) <...>-5856 0D..2 618us : __schedule <-0> (20 162) <...>-5856 0D..2 619us : __spin_unlock_irq (__schedule) <...>-5856 0...1 619us : trace_stop_sched_switched (__schedule) <...>-5856 0D..1 619us : trace_stop_sched_switched <<...>-5856> (37 0) what is visible in this trace is that CPU#1 ran try_to_wake_up() for PID:5856, it placed PID:5856 on CPU#0's runqueue and ran resched_task() for CPU#0. But it decided to not send an IPI that no CPU - due to TS_POLLING. But CPU#0 never woke up after its NEED_RESCHED bit was set, and only rescheduled to PID:5856 upon the next lapic timer IRQ. The result was a 600+ usecs latency and a missed wakeup! the bug turned out to be an idle-wakeup bug introduced into the mainline kernel this summer via an optimization in the x86_64 tree: commit 495ab9c045e1b0e5c82951b762257fe1c9d81564 Author: Andi Kleen Date: Mon Jun 26 13:59:11 2006 +0200 [PATCH] i386/x86-64/ia64: Move polling flag into thread_info_status During some profiling I noticed that default_idle causes a lot of memory traffic. I think that is caused by the atomic operations to clear/set the polling flag in thread_info. There is actually no reason to make this atomic - only the idle thread does it to itself, other CPUs only read it. So I moved it into ti->status. the problem is this type of change: if (!hlt_counter && boot_cpu_data.hlt_works_ok) { - clear_thread_flag(TIF_POLLING_NRFLAG); + current_thread_info()->status &= ~TS_POLLING; smp_mb__after_clear_bit(); while (!need_resched()) { local_irq_disable(); this changes clear_thread_flag() to an explicit clearing of TS_POLLING. clear_thread_flag() is defined as: clear_bit(flag, &ti->flags); and clear_bit() is a LOCK-ed atomic instruction on all x86 platforms: static inline void clear_bit(int nr, volatile unsigned long * addr) { __asm__ __volatile__( LOCK_PREFIX "btrl %1,%0" hence smp_mb__after_clear_bit() is defined as a simple compile barrier: #define smp_mb__after_clear_bit() barrier() but the explicit TS_POLLING clearing introduced by the patch: + current_thread_info()->status &= ~TS_POLLING; is not an atomic op! So the clearing of the TS_POLLING bit is freely reorderable with the reading of the NEED_RESCHED bit - and both now reside in different memory addresses. CPU idle wakeup very much depends on ordered memory ops, the clearing of the TS_POLLING flag must always be done before we test need_resched() and hit the idle instruction(s). [Symmetrically, the wakeup code needs to set NEED_RESCHED before it tests the TS_POLLING flag, so memory ordering is paramount.] Fernando's dual-core Athlon64 system has a sufficiently advanced memory ordering model so that it triggered this scenario very often. ( And it also turned out that the reason why these latencies never triggered on my testsystems is that i routinely use idle=poll, which was the only idle variant not affected by this bug. ) The fix is to change the smp_mb__after_clear_bit() to an smp_mb(), to act as an absolute barrier between the TS_POLLING write and the NEED_RESCHED read. This affects almost all idling methods (default, ACPI, APM), on all 3 x86 architectures: i386, x86_64, ia64. Signed-off-by: Ingo Molnar Tested-by: Fernando Lopez-Lezcano [chrisw: backport to 2.6.19.1] Signed-off-by: Chris Wright

[PATCH] x86-64: Mark rdtsc as sync only for netburst, not for core2

2007-01-10T19:05:17Z

On the Core2 cpus, the rdtsc instruction is not serializing (as defined in the architecture reference since rdtsc exists) and due to the deep speculation of these cores, it's possible that you can observe time go backwards between cores due to this speculation. Since the kernel already deals with this with the SYNC_RDTSC flag, the solution is simple, only assume that the instruction is serializing on family 15... The price one pays for this is a slightly slower gettimeofday (by a dozen or two cycles), but that increase is quite small to pay for a really-going-forward tsc counter. Signed-off-by: Arjan van de Ven Signed-off-by: Andi Kleen Signed-off-by: Chris Wright

[PATCH] x86: Fix boot hang due to nmi watchdog init code

2006-12-11T19:32:40Z

2.6.19 stopped booting (or booted based on build/config) on our x86_64 systems due to a bug introduced in 2.6.19. check_nmi_watchdog schedules an IPI on all cpus to busy wait on a flag, but fails to set the busywait flag if NMI functionality is disabled. This causes the secondary cpus to spin in an endless loop, causing the kernel bootup to hang. Depending upon the build, the busywait flag got overwritten (stack variable) and caused the kernel to bootup on certain builds. Following patch fixes the bug by setting the busywait flag before returning from check_nmi_watchdog. I guess using a stack variable is not good here as the calling function could potentially return while the busy wait loop is still spinning on the flag. AK: I redid the patch significantly to be cleaner Signed-off-by: Ravikiran Thirumalai Signed-off-by: Shai Fultheim Signed-off-by: Andi Kleen Signed-off-by: Chris Wright

Merge branch 'for-linus' of git://one.firstfloor.org/home/andi/git/linux-2.6

2006-11-29T01:28:41Z

* 'for-linus' of git://one.firstfloor.org/home/andi/git/linux-2.6: [PATCH] x86-64: Use stricter in process stack check for unwinder [PATCH] i386: Fix compilation with UP genericarch [PATCH] x86-64: Fix warning in io_apic.c [PATCH] x86-64: work around gcc4 issue with -Os in Dwarf2 stack unwind [PATCH] x86_64: Align data segment to PAGE_SIZE boundary

[PATCH] x86-64: Use stricter in process stack check for unwinder

2006-11-28T19:12:59Z

Previously it would check for alignment only, which could break if the stack pointer was unaligned. Now explicitely check if the stack pointer is in the stack page of the current process. Ported from i386. Signed-off-by: Andi Kleen

[PATCH] x86-64: Fix warning in io_apic.c

2006-11-28T19:12:59Z

[PATCH] x86_64: fix 'earlyprintk=...,keep' regression

2006-11-28T18:58:21Z

Commit 2c8c0e6b8d7700a990da8d24eff767f9ca223b96 ("[PATCH] Convert x86-64 to early param") broke the earlyprintk=...,keep feature. This restores that functionality. Tested on x86_64. Must-have for v2.6.19, no risk. Signed-off-by: Ingo Molnar Signed-off-by: Linus Torvalds

[PATCH] x86_64: Align data segment to PAGE_SIZE boundary

2006-11-21T09:31:21Z

o Explicitly align data segment to PAGE_SIZE boundary otherwise depending on config options and tool chain it might be placed on a non PAGE_SIZE aligned boundary and vmlinux loaders like kexec fail when they encounter a PT_LOAD type segment which is not aligned to PAGE_SIZE boundary. Signed-off-by: Vivek Goyal Signed-off-by: Andi Kleen