On reboot or poweroff (machine_shutdown()) a call to smp_send_stop() is
made (to stop the others CPU's) when CONFIG_SMP=y.
arch/arm/kernel/process.c:
void machine_shutdown(void)
{
#ifdef CONFIG_SMP
smp_send_stop();
#endif
}
smp_send_stop() calls the function pointer smp_cross_call(), which is set
on the smp_init_cpus() function for OMAP processors.
arch/arm/mach-omap2/omap-smp.c:
void __init smp_init_cpus(void)
{
...
set_smp_cross_call(gic_raise_softirq);
...
}
But the ARM setup_arch() function only calls smp_init_cpus()
if CONFIG_SMP=y && is_smp().
arm/kernel/setup.c:
void __init setup_arch(char **cmdline_p)
{
...
#ifdef CONFIG_SMP
if (is_smp())
smp_init_cpus();
#endif
...
}
Newer OMAP CPU's are SMP machines so omap2plus_defconfig sets
CONFIG_SMP=y. Unfortunately on an OMAP UP machine is_smp()
returns false and smp_init_cpus() is never called and the
smp_cross_call() function remains NULL.
If the machine is rebooted or powered off, smp_send_stop() will
be called (since CONFIG_SMP=y) leading to the following error:
[ 42.815551] Restarting system.
[ 42.819030] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[ 42.827667] pgd = d7a74000
[ 42.830566] [00000000] *pgd=96ce7831, *pte=00000000, *ppte=00000000
[ 42.837249] Internal error: Oops: 80000007 [#1] SMP ARM
[ 42.842773] Modules linked in:
[ 42.846008] CPU: 0 Not tainted (3.5.0-rc3-next-20120622-00002-g62e87ba-dirty #44)
[ 42.854278] PC is at 0x0
[ 42.856994] LR is at smp_send_stop+0x4c/0xe4
[ 42.861511] pc : [<00000000>] lr : [<c00183a4>] psr: 60000013
[ 42.861511] sp : d6c85e70 ip : 00000000 fp : 00000000
[ 42.873626] r10: 00000000 r9 : d6c84000 r8 : 00000002
[ 42.879150] r7 : c07235a0 r6 : c06dd2d0 r5 : 000f4241 r4 : d6c85e74
[ 42.886047] r3 : 00000000 r2 : 00000000 r1 : 00000006 r0 : d6c85e74
[ 42.892944] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
[ 42.900482] Control: 10c5387d Table: 97a74019 DAC: 00000015
[ 42.906555] Process reboot (pid: 1166, stack limit = 0xd6c842f8)
[ 42.912902] Stack: (0xd6c85e70 to 0xd6c86000)
[ 42.917510] 5e60: c07235a0 00000000 00000000 d6c84000
[ 42.926177] 5e80: 01234567 c00143d0 4321fedc c00511bc d6c85ebc 00000168 00000460 00000000
[ 42.934814] 5ea0: c1017950 a0000013 c1017900 d8014390 d7ec3858 c0498e48 c1017950 00000000
[ 42.943481] 5ec0: d6ddde10 d6c85f78 00000003 00000000 d6ddde10 d6c84000 00000000 00000000
[ 42.952117] 5ee0: 00000002 00000000 00000000 c0088c88 00000002 00000000 00000000 c00f4b90
[ 42.960784] 5f00: 00000000 d6c85ebc d8014390 d7e311c8 60000013 00000103 00000002 d6c84000
[ 42.969421] 5f20: c00f3274 d6e00a00 00000001 60000013 d6c84000 00000000 00000000 c00895d4
[ 42.978057] 5f40: 00000002 d8007c80 d781f000 c00f6150 d8010cc0 c00f3274 d781f000 d6c84000
[ 42.986694] 5f60: c0013020 d6e00a00 00000001 20000010 0001257c ef000000 00000000 c00895d4
[ 42.995361] 5f80: 00000002 00000001 00000003 00000000 00000001 00000003 00000000 00000058
[ 43.003997] 5fa0: c00130c8 c0012f00 00000001 00000003 fee1dead 28121969 01234567 00000002
[ 43.012634] 5fc0: 00000001 00000003 00000000 00000058 00012584 0001257c 00000001 00000000
[ 43.021270] 5fe0: 000124bc bec5cc6c 00008f9c 4a2f7c40 20000010 fee1dead 00000000 00000000
[ 43.029968] [<c00183a4>] (smp_send_stop+0x4c/0xe4) from [<c00143d0>] (machine_restart+0xc/0x4c)
[ 43.039154] [<c00143d0>] (machine_restart+0xc/0x4c) from [<c00511bc>] (sys_reboot+0x144/0x1f0)
[ 43.048278] [<c00511bc>] (sys_reboot+0x144/0x1f0) from [<c0012f00>] (ret_fast_syscall+0x0/0x3c)
[ 43.057464] Code: bad PC value
[ 43.060760] ---[ end trace c3988d1dd0b8f0fb ]---
Add a check so smp_cross_call() is only called when there is more than one CPU on-line.
Cc: <stable@vger.kernel.org>
Signed-off-by: Javier Martinez Canillas <javier at dowhile0.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
While running hotplug tests I ran into this RCU splat
===============================
[ INFO: suspicious RCU usage. ]
3.4.0 #3275 Tainted: G W
-------------------------------
include/linux/rcupdate.h:729 rcu_read_lock() used illegally while idle!
other info that might help us debug this:
RCU used illegally from idle CPU!
rcu_scheduler_active = 1, debug_locks = 0
RCU used illegally from extended quiescent state!
4 locks held by swapper/2/0:
#0: ((cpu_died).wait.lock){......}, at: [<c00ab128>] complete+0x1c/0x5c
#1: (&p->pi_lock){-.-.-.}, at: [<c00b275c>] try_to_wake_up+0x2c/0x388
#2: (&rq->lock){-.-.-.}, at: [<c00b2860>] try_to_wake_up+0x130/0x388
#3: (rcu_read_lock){.+.+..}, at: [<c00abe5c>] cpuacct_charge+0x28/0x1f4
stack backtrace:
[<c001521c>] (unwind_backtrace+0x0/0x12c) from [<c00abec8>] (cpuacct_charge+0x94/0x1f4)
[<c00abec8>] (cpuacct_charge+0x94/0x1f4) from [<c00b395c>] (update_curr+0x24c/0x2c8)
[<c00b395c>] (update_curr+0x24c/0x2c8) from [<c00b59c4>] (enqueue_task_fair+0x50/0x194)
[<c00b59c4>] (enqueue_task_fair+0x50/0x194) from [<c00afea4>] (enqueue_task+0x30/0x34)
[<c00afea4>] (enqueue_task+0x30/0x34) from [<c00b0908>] (ttwu_activate+0x14/0x38)
[<c00b0908>] (ttwu_activate+0x14/0x38) from [<c00b28a8>] (try_to_wake_up+0x178/0x388)
[<c00b28a8>] (try_to_wake_up+0x178/0x388) from [<c00a82a0>] (__wake_up_common+0x34/0x78)
[<c00a82a0>] (__wake_up_common+0x34/0x78) from [<c00ab154>] (complete+0x48/0x5c)
[<c00ab154>] (complete+0x48/0x5c) from [<c07db7cc>] (cpu_die+0x2c/0x58)
[<c07db7cc>] (cpu_die+0x2c/0x58) from [<c000f954>] (cpu_idle+0x64/0xfc)
[<c000f954>] (cpu_idle+0x64/0xfc) from [<80208160>] (0x80208160)
When a cpu is marked offline during its idle thread it calls
cpu_die() during an RCU idle period. cpu_die() calls complete()
to notify the killing process that the cpu has died. complete()
calls into the scheduler code and eventually grabs an RCU read
lock in cpuacct_charge().
Mark complete() as RCU_NONIDLE so that RCU pays attention to this
CPU for the duration of the complete() function even though it's
in idle.
Suggested-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Checking for process->mm is not enough because process' main thread may exit or detach its mm via use_mm(), but other threads may still have a valid mm. To fix this we would need to use find_lock_task_mm(), which would walk up all threads and returns an appropriate task (with task lock held). clear_tasks_mm_cpumask() has this issue fixed, so let's use it. Suggested-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org> Cc: Russell King <rmk@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull smp hotplug cleanups from Thomas Gleixner:
"This series is merily a cleanup of code copied around in arch/* and
not changing any of the real cpu hotplug horrors yet. I wish I'd had
something more substantial for 3.5, but I underestimated the lurking
horror..."
Fix up trivial conflicts in arch/{arm,sparc,x86}/Kconfig and
arch/sparc/include/asm/thread_info_32.h
* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (79 commits)
um: Remove leftover declaration of alloc_task_struct_node()
task_allocator: Use config switches instead of magic defines
sparc: Use common threadinfo allocator
score: Use common threadinfo allocator
sh-use-common-threadinfo-allocator
mn10300: Use common threadinfo allocator
powerpc: Use common threadinfo allocator
mips: Use common threadinfo allocator
hexagon: Use common threadinfo allocator
m32r: Use common threadinfo allocator
frv: Use common threadinfo allocator
cris: Use common threadinfo allocator
x86: Use common threadinfo allocator
c6x: Use common threadinfo allocator
fork: Provide kmemcache based thread_info allocator
tile: Use common threadinfo allocator
fork: Provide weak arch_release_[task_struct|thread_info] functions
fork: Move thread info gfp flags to header
fork: Remove the weak insanity
sh: Remove cpu_idle_wait()
...
Reason: Pull in the separate branch which was created so arch/tile can base further work on it. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Commit 4e8ee7de227e3ab9a72040b448ad728c5428a042 (ARM: SMP: use idmap_pgd for mapping MMU enable during secondary booting) switched secondary boot to use idmap_pgd, which is initialized during early_initcall, instead of a page table initialized during __cpu_up. This causes idmap_pgd to contain the static mappings but be missing all dynamic mappings. If a console is registered that creates a dynamic mapping, the printk in secondary_start_kernel will trigger a data abort on the missing mapping before the exception handlers have been initialized, leading to a hang. Initial boot is not affected because no consoles have been registered, and resume is usually not affected because the offending console is suspended. Onlining a cpu with hotplug triggers the problem. A workaround is to the printk in secondary_start_kernel until after the page tables have been switched back to init_mm. Cc: <stable@vger.kernel.org> Signed-off-by: Colin Cross <ccross@android.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
When performing a kexec on an SMP system, the secondary cores are stopped by calling machine_shutdown(), which in turn issues IPIs to offline the other CPUs. Unfortunately, this isn't enough to reboot the cores into a new kernel (since they are just executing a cpu_relax loop somewhere in memory) so we make use of platform_cpu_kill, part of the CPU hotplug implementation, to place the cores somewhere safe. This function expects to be called on the killing CPU for each core that it takes out. This patch moves the platform_cpu_kill callback out of the IPI handler and into smp_send_stop, therefore ensuring that it executes on the killing CPU rather than on the victim, matching what the hotplug code requires. Cc: stable@vger.kernel.org Reported-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
When running an SMP_ON_UP enabled kernel on UP, or with nosmp passed to the kernel, we want to be able to detect that a local timer is not going to be used (local timers are only used on SMP platforms), so we could register it as a global timer instead. Return -ENXIO when the above case is detected. Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> Cc: Russell King <linux@arm.linux.org.uk> Tested-by: Frank Rowand <frank.rowand@am.sony.com> Link: http://lkml.kernel.org/r/20120420124557.448826362@linutronix.de