Re: [PATCH] parisc: Improve alternative live patching

[John David Anglin <dave.anglin@xxxxxxxx>]

On 2018-11-09 2:54 a.m., Helge Deller wrote:
> On 09.11.2018 08:25, Helge Deller wrote:
> > On 09.11.2018 01:11, John David Anglin wrote:
> > > On 2018-11-08 5:03 p.m., Helge Deller wrote:
> > > >    static inline int arch_spin_is_locked(arch_spinlock_t *x)
> > > >    {
> > > > -    volatile unsigned int *a = __ldcw_align(x);
> > > > +    volatile unsigned int *a;
> > > > +
> > > > +    if (asm_online_cpus() == 1)
> > > > +        return 1;
> > > I think the return value should be 0 (unlocked) when asm_online_cpus() == 1.
> > In that case, booting with 4 CPUs is working then, but when booting with only one CPU you get:
> I think it's a inconsistency in Linux code.
>
> [deller@ls3530 linux-2.6]$ grep -r assert_raw_spin_locked
> include/linux/spinlock.h:#define assert_spin_locked(lock)       assert_raw_spin_locked(&(lock)->rlock)
> include/linux/spinlock_api_up.h:#define assert_raw_spin_locked(lock)    do { (void)(lock); } while (0)
> include/linux/spinlock_api_smp.h:#define assert_raw_spin_locked(x)      BUG_ON(!raw_spin_is_locked(x))
>
> For UP, it's assumed the lock is held anyway, and assert_raw_spin_locked() is a NOP.
> For SMP, raw_spin_is_locked() is always called and checked.
> So, for our live patching we probably need to simulate that the lock is locked for asm_online_cpus() == 1
> and thus we need to return 1 in arch_spin_is_locked().
You are correct.  arch_spin_is_locked() should return 1.  Except for one 
startup situation, it is only called
from debug_spin_unlock() where it is expected that the lock is held.

Dave
>   
> > [    0.000000] Linux version 4.20.0-rc1-32bit+ (deller@ls3530) (gcc version 7.2.1 20170915 (Red Hat Cross 7.2.1-1) (GCC)) #943 SMP Fri Nov 9 08:08:13 CET 2018
> > [    0.000000] CPU0: thread -1, cpu 0, socket 0
> > [    0.000000] FP[0] enabled: Rev 1 Model 19
> > [    0.000000] The 32-bit Kernel has started...
> > [    0.000000] Kernel default page size is 4 KB. Huge pages disabled.
> > [    0.000000] printk: bootconsole [ttyB0] enabled
> > [    0.000000] Initialized PDC Console for debugging.
> > [    0.000000] Determining PDC firmware type: System Map.
> > [    0.000000] model 00005020 00000481 00000000 02020202 7794d7fe 100000f0 00000004 000000ba 000000ba
> > [    0.000000] vers  00000008
> > [    0.000000] CPUID vers 15 rev 8 (0x000001e8)
> > [    0.000000] capabilities 0x2
> > [    0.000000] model 9000/778/B160L
> > [    0.000000] Memory Ranges:
> > [    0.000000]  0) Start 0x0000000000000000 End 0x000000001fffffff Size    512 MB
> > [    0.000000] Total Memory: 512 MB
> > [    0.000000] PDT: Firmware does not provide any page deallocation information.
> > [    0.000000] percpu: Embedded 22 pages/cpu @(ptrval) s61328 r8192 d20592 u90112
> > [    0.000000] SMP: bootstrap CPU ID is 0
> > [    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: 129920
> > [    0.000000] Kernel command line: console=ttyS0 root=/dev/sda5 cryptomgr.notests
> > [    0.000000] Dentry cache hash table entries: 65536 (order: 6, 262144 bytes)
> > [    0.000000] Inode-cache hash table entries: 32768 (order: 5, 131072 bytes)
> > [    0.000000] Memory: 507412K/524288K available (7140K kernel code, 1036K rwdata, 1651K rodata, 780K init, 376K bss, 16876K reserved, 0K cma-reserved)
> > [    0.000000] rcu: Hierarchical RCU implementation.
> > [    0.000000] rcu: RCU calculated value of scheduler-enlistment delay is 10 jiffies.
> > [    0.000000] NR_IRQS: 96
> > [    0.000298] sched_clock: 32 bits at 250MHz, resolution 4ns, wraps every 8589934590ns
> > [    0.007222] Console: colour dummy device 128x48
> > [    0.008833] Calibrating delay loop... 1661.33 BogoMIPS (lpj=8306688)
> > [    0.232493] pid_max: default: 32768 minimum: 301
> > [    0.236972] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
> > [    0.237480] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
> > [    0.285070] rcu: Hierarchical SRCU implementation.
> > [    0.292563] smp: Bringing up secondary CPUs ...
> > [    0.293128] smp: Brought up 1 node, 1 CPU
> > [    0.306444] devtmpfs: initialized
> > [    0.320533] random: get_random_u32 called from bucket_table_alloc+0x1ac/0x1d4 with crng_init=0
> > [    0.326747] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
> > [    0.328413] futex hash table entries: 1024 (order: 3, 49152 bytes)
> > [    0.341270] NET: Registered protocol family 16
> > [    0.352413] EISA bus registered
> > [    0.354398] Searching for devices...
> > [    0.364975] Found devices:
> > [    0.366163] 1. Phantom PseudoBC GSC+ Port at 0xffc00000 [8] { 7, 0x0, 0x504, 0x00000 }
> > [    0.367071] 2. Dino PCI Bridge at 0xfff80000 [8/0] { 13, 0x3, 0x680, 0x0000a }
> > [    0.367621] 3. Merlin+ 132 Dino RS-232 at 0xfff83000 [8/0/63] { 10, 0x0, 0x022, 0x0008c }
> > [    0.368216] 4. Merlin L2 160 (9000/778/B160L) at 0xfff10000 [62] { 0, 0x0, 0x502, 0x00004 }
> > [    0.368799] 5. Memory at 0xfffbf000 [63] { 1, 0x0, 0x067, 0x00009 }
> > [    0.371441] CPU(s): 1 out of 1 PA7300LC (PCX-L2) at 250.000000 MHz online
> > [    0.378172] alternatives: applied 10030 out of 10030 patches
> > [    0.378648] BUG: spinlock already unlocked on CPU#0, swapper/0/1
> > [    0.378648]  lock: logbuf_lock+0x0/0x1c, .magic: dead4ead, .owner: swapper/0/1, .owner_cpu: 0
> > [    0.378648] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.20.0-rc1-32bit+ #943
> > [    0.378648] Hardware name: 9000/778/B160L
> > [    0.378648] Backtrace:
> > [    0.378648]  [<101c728c>] show_stack+0x48/0x5c
> > [    0.378648]  [<1089a3e0>] dump_stack+0x80/0x134
> > [    0.378648]  [<1024f734>] spin_bug+0xc4/0xec
> > [    0.378648]  [<1024f9e4>] do_raw_spin_unlock+0x7c/0xfc
> > [    0.378648]  [<108b9ed0>] _raw_spin_unlock+0x38/0x4c
> > [    0.378648]  [<10255de4>] vprintk_emit+0xe8/0x234
> > [    0.378648]  [<10256110>] vprintk_default+0x54/0x6c
> > [    0.378648]  [<10256f74>] vprintk_func+0x148/0x158
> > [    0.378648]  [<102566f8>] printk+0x54/0x6c
> > [    0.378648]  [<101d4354>] apply_alternatives+0xc4/0x1c4
> > [    0.378648]  [<10107ca8>] 0x10107ca8
> > [    0.378648]  [<10105e24>] 0x10105e24
> > [    0.378648]  [<101c39a8>] do_one_initcall+0xd0/0x1dc
> > [    0.378648]  [<101017b0>] 0x101017b0
> > [    0.378648]  [<108b2320>] kernel_init+0x34/0x158
> > [    0.378648]  [<101cc01c>] ret_from_kernel_thread+0x1c/0x24
> > [    0.378648]
> > [    0.379288] Whole cache flush 12773 cycles, flushing 10448896 bytes 4675 cycles
> > [    0.379735] Cache flush threshold set to 512 KiB
> > [    0.393941] Whole TLB flush 10612 cycles, Range flush 10448896 bytes 1450591 cycles
> > [    0.394391] Calculated TLB flush threshold 4 KiB
> > [    0.394677] TLB flush threshold set to 16 KiB
> > [    0.397494] Dino version 3.1 found at 0xfff80000
> > [    0.401648] ------------[ cut here ]------------
> > [    0.401948] kernel BUG at /home/cvs/LINUX/git-kernel/linux-2.6/mm/slab.c:2910!
> > [    0.402565] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.20.0-rc1-32bit+ #943
> > [    0.402903] Hardware name: 9000/778/B160L
> > [    0.403262]
> > [    0.403489]      YZrvWESTHLNXBCVMcbcbcbcbOGFRQPDI
> > [    0.404065] PSW: 00000000000001001011111100001110 Not tainted
> > [    0.404668] r00-03  0004bf0e 10b1d670 10369034 2f4bc900
> > [    0.404979] r04-07  2f401190 00000000 2f4001c0 2fb391a8
> > [    0.405238] r08-11  101a01a8 0000003c 1f999000 00000200
> > [    0.405495] r12-15  10ac7064 006080c0 2f4011ac 2f4011b4
> > [    0.405942] r16-19  007fffff 00000200 00000020 00000000
> > [    0.406450] r20-23  00000001 10b162a4 00000000 00000000
> > [    0.407061] r24-27  2f4bc900 10368ffc 102af2d0 10ac6670
> > [    0.407777] r28-31  2f40119f 000affff 2f4bc940 105a27f0
> > [    0.408534] sr00-03  00000000 00000000 00000000 00000000
> > [    0.409727] sr04-07  00000000 00000000 00000000 00000000
> > [    0.410404]
> > [    0.410737] IASQ: 00000000 00000000 IAOQ: 10369050 10369054
> > [    0.411122]  IIR: 03ffe01f    ISR: 00000000  IOR: 10369000
> > [    0.411419]  CPU:        0   CR30: 2f4bc000 CR31: 00000000
> > [    0.411700]  ORIG_R28: 00000000
> > [    0.411962]  IAOQ[0]: get_first_slab+0x54/0xd8
> > [    0.412219]  IAOQ[1]: get_first_slab+0x58/0xd8
> > [    0.412467]  RP(r2): get_first_slab+0x38/0xd8
> > [    0.412720] Backtrace:
> > [    0.412908]  [<1036a254>] cache_alloc_refill+0x278/0x474
> > [    0.413186]  [<1036b570>] __kmalloc+0x210/0x22c
> > [    0.413445]  [<101f5580>] resource_list_create_entry+0x48/0x7c
> > [    0.413770]  [<1057f2b4>] pci_add_resource_offset+0x48/0x98
> > [    0.414083]  [<10133058>] 0x10133058
> > [    0.414306]  [<101d3348>] parisc_driver_probe+0x48/0x6c
> > [    0.414603]  [<10622734>] really_probe+0x2a8/0x3c8
> > [    0.414877]  [<10622ec4>] driver_probe_device+0x4dc/0x4e4
> > [    0.415157]  [<10622f84>] __driver_attach+0xb8/0x110
> > [    0.415426]  [<1061fe48>] bus_for_each_dev+0xa0/0xd8
> > [    0.415771]  [<10621e10>] driver_attach+0x48/0x5c
> > [    0.416086]  [<106216f4>] bus_add_driver+0x1c0/0x20c
> > [    0.416429]  [<10623ac0>] driver_register+0xec/0x12c
> > [    0.416761]  [<101d3520>] register_parisc_driver+0xac/0xb4
> > [    0.417115]  [<10133478>] 0x10133478
> > [    0.417362]  [<10105e64>] 0x10105e64
> > [    0.417633]  [<101c39a8>] do_one_initcall+0xd0/0x1dc
> > [    0.417960]  [<101017b0>] 0x101017b0
> > [    0.418238]  [<108b2320>] kernel_init+0x34/0x158
> > [    0.418785]  [<101cc01c>] ret_from_kernel_thread+0x1c/0x24
> > [    0.419181]
> > [    0.419490] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.20.0-rc1-32bit+ #943
> > [    0.420044] Hardware name: 9000/778/B160L
> > [    0.420337] Backtrace:
> > [    0.420519]  [<101c728c>] show_stack+0x48/0x5c
> > [    0.420789]  [<1089a3e0>] dump_stack+0x80/0x134
> > [    0.421048]  [<101c7468>] die_if_kernel+0x18c/0x1e8
> > [    0.421330]  [<101c7984>] handle_interruption+0x2ec/0x730
> > [    0.421710]  [<10369050>] get_first_slab+0x54/0xd8
> > [    0.421990]  [<1036a254>] cache_alloc_refill+0x278/0x474
> > [    0.422432]  [<1036b570>] __kmalloc+0x210/0x22c
> > [    0.422797]  [<101f5580>] resource_list_create_entry+0x48/0x7c
> > [    0.423267]  [<1057f2b4>] pci_add_resource_offset+0x48/0x98
> > [    0.423724]  [<10133058>] 0x10133058
> > [    0.424023]  [<101d3348>] parisc_driver_probe+0x48/0x6c
> > [    0.424474]  [<10622734>] really_probe+0x2a8/0x3c8
> > [    0.424863]  [<10622ec4>] driver_probe_device+0x4dc/0x4e4
> > [    0.425303]  [<10622f84>] __driver_attach+0xb8/0x110
> > [    0.425716]  [<1061fe48>] bus_for_each_dev+0xa0/0xd8
> > [    0.426155]  [<10621e10>] driver_attach+0x48/0x5c
> > [    0.426553]  [<106216f4>] bus_add_driver+0x1c0/0x20c
> > [    0.426978]  [<10623ac0>] driver_register+0xec/0x12c
> > [    0.427428]  [<101d3520>] register_parisc_driver+0xac/0xb4
> > [    0.427843]  [<10133478>] 0x10133478
> > [    0.428148]  [<10105e64>] 0x10105e64
> > [    0.428509]  [<101c39a8>] do_one_initcall+0xd0/0x1dc
> > [    0.428648]  [<101017b0>] 0x101017b0
> > [    0.428648]  [<108b2320>] kernel_init+0x34/0x158
> > [    0.428648]  [<101cc01c>] ret_from_kernel_thread+0x1c/0x24
> > [    0.428648]
> > [    0.429129] ---[ end trace 1a6ae02625c0f6ff ]---
> > [    0.431183] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
> > [    0.432304] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---


--
John David Anglin  dave.anglin@xxxxxxxx