Hello lkml, Booting ixp4xx/ARM/BE with lockdep enabled to test my code, I got a lockdep warning (see below). Does it mean that soft-lockup detector is started too early ? Any advice how to approach and fix the problem are appreciated very much. If CONFIG_DETECT_SOFTLOCKUP=n, lockdep does not complain.
Kernel is vanilla 2.6.21-rc4 + lockdep-stacktrace.diff from http://svn.wantstofly.org/kernel/ repository. [ 0.000000] Linux version 2.6.21-rc4 ([EMAIL PROTECTED]) (gcc version 4.2.0 20070207 (prerelease) (http://www.wilibox.com)) #12 Fri Mar 16 16:05:39 EET 2007 [ 0.000000] CPU: XScale-IXP42x Family [690541f1] revision 1 (ARMv5TE), cr=000039ff [ 0.000000] Machine: Intel IXDP425 Development Platform [ 0.000000] Memory policy: ECC disabled, Data cache writeback ... [ 0.000000] Built 1 zonelists. Total pages: 16256 [ 0.000000] Kernel command line: initcall_debug loglevel=8 i2c_debug=9 root=/dev/mtdblock2 console=ttyS0,115200 ro init=/linuxrc [ 0.000000] PID hash table entries: 256 (order: 8, 1024 bytes) [ 0.000000] Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar [ 0.000000] ... MAX_LOCKDEP_SUBCLASSES: 8 [ 0.000000] ... MAX_LOCK_DEPTH: 30 [ 0.000000] ... MAX_LOCKDEP_KEYS: 2048 [ 0.000000] ... CLASSHASH_SIZE: 1024 [ 0.000000] ... MAX_LOCKDEP_ENTRIES: 8192 [ 0.000000] ... MAX_LOCKDEP_CHAINS: 16384 [ 0.000000] ... CHAINHASH_SIZE: 8192 [ 0.000000] memory used by lock dependency info: 1096 kB [ 0.000000] per task-struct memory footprint: 1200 bytes [ 0.000000] ------------------------ [ 0.000000] | Locking API testsuite: ... <skiped> ... [ 0.590000] ------------------------------------------------------- [ 0.590000] Good, all 218 testcases passed! | [ 0.590000] --------------------------------- [ 0.590000] Dentry cache hash table entries: 8192 (order: 3, 32768 bytes) [ 0.600000] Calibrating delay loop... 265.42 BogoMIPS (lpj=1327104) [ 0.840000] Mount-cache hash table entries: 512 [ 0.840000] CPU: Testing write buffer coherency: ok [ 0.840000] INFO: trying to register non-static key. [ 0.840000] the code is fine but needs lockdep annotation. [ 0.840000] turning off the locking correctness validator. Don't know how to fix that. [ 0.840000] [<c0021018>] (dump_stack+0x0/0x14) from [<c0052ccc>] (__lock_acquire+0x640/0x1110) [ 0.840000] [<c005268c>] (__lock_acquire+0x0/0x1110) from [<c0053820>] (lock_acquire+0x84/0x98) [ 0.840000] [<c005379c>] (lock_acquire+0x0/0x98) from [<c01858b4>] (_spin_lock_irqsave+0x48/0x5c) [ 0.840000] [<c018586c>] (_spin_lock_irqsave+0x0/0x5c) from [<c002f358>] (sched_setscheduler+0xd4/0x2a8) [ 0.840000] r6 = C04D6000 r5 = C04D1820 r4 = 00000001 [ 0.840000] [<c002f284>] (sched_setscheduler+0x0/0x2a8) from [<c0058848>] (watchdog+0x30/0x6c) [ 0.840000] [<c0058818>] (watchdog+0x0/0x6c) from [<c00494ec>] (kthread+0x108/0x118) [ 0.840000] r4 = 00000000 [ 0.840000] [<c00493e4>] (kthread+0x0/0x118) from [<c0036098>] (do_exit+0x0/0x894) [ 0.840000] r7 = 00000000 r6 = 00000000 r5 = 00000000 r4 = 00000000 [ 0.840000] Calling initcall 0xc0009980: ptrace_break_init+0x0/0x2c() With gdb it points to *__task_rq_lock(struct task_struct *p) (gdb) l *sched_setscheduler+0xd4 0x1644 is in sched_setscheduler (kernel/sched.c:395). 390 { 391 struct rq *rq; 392 393 repeat_lock_task: 394 rq = task_rq(p); 395 spin_lock(&rq->lock); 396 if (unlikely(rq != task_rq(p))) { 397 spin_unlock(&rq->lock); 398 goto repeat_lock_task; 399 } (gdb) I think it is really about ->pi_lock, on line 4134, that lockdep doesn't know anything about. 4130 /* 4131 * make sure no PI-waiters arrive (or leave) while we are 4132 * changing the priority of the task: 4133 */ 4134 spin_lock_irqsave(&p->pi_lock, flags); 4135 /* 4136 * To be able to change p->policy safely, the apropriate 4137 * runqueue lock must be held. 4138 */ 4139 rq = __task_rq_lock(p); Best regards, Žilvinas Valinskas - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
