Mathieu Desnoyers sent a patch earlier that should address this problem. http://lkml.indiana.edu/hypermail/linux/kernel/0906.1/00331.html Thanks, Venki On Tue, 2009-06-23 at 11:40 -0700, Ingo Molnar wrote: > * Ingo Molnar <mingo@xxxxxxx> wrote: > > > * Thomas Renninger <trenn@xxxxxxx> wrote: > > > > > > Note, this bug warning still triggers rather frequently with > > > > latest -git (fb20871) during bootup on two test-systems - > > > > relevant portion of the bootlog attached below. As usual i can > > > > test any fix for this. > > > > > > Best rip out the dbs_mutex in drivers/cpufreq/cpufreq_ondemand.c > > > totally. I can provide several locking cleanups for cpufreq for > > > .31 the next days, including dbs_mutex removal, which I think is > > > not needed. The dbs_mutex removal which should fix this could then > > > be marked: CC: stable@xxxxxxxxxx > > > > drivers/cpufreq/cpufreq_conservative.c too i guess? > > > > Something like the patch below? > > > > Utterly untested and such. > > i tested it and this blatant blind ripping out of a layer of locking > uncovered the next layer: > > [ 144.961483] ======================================================= > [ 144.961685] [ INFO: possible circular locking dependency detected ] > [ 144.961785] 2.6.30-tip-08973-gb747c8d-dirty #6295 > [ 144.961878] ------------------------------------------------------- > [ 144.961974] S99local/8461 is trying to acquire lock: > [ 144.962016] (&(&dbs_info->work)->work){+.+...}, at: [<c109962a>] wait_on_work+0x0/0xba > [ 144.962016] > [ 144.962016] but task is already holding lock: > [ 144.962016] (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [<c1f5dd3f>] lock_policy_rwsem_write+0x73/0xec > [ 144.962016] > [ 144.962016] which lock already depends on the new lock. > > (see below for the full details) > > I guess someone who knows the cpufreq code will have to fix the > locking in this code for real. > > Ingo > > [ 144.767335] CPUFREQ: ondemand sampling_rate_max sysfs file is deprecated - used by: cat > [ 144.961480] > [ 144.961483] ======================================================= > [ 144.961685] [ INFO: possible circular locking dependency detected ] > [ 144.961785] 2.6.30-tip-08973-gb747c8d-dirty #6295 > [ 144.961878] ------------------------------------------------------- > [ 144.961974] S99local/8461 is trying to acquire lock: > [ 144.962016] (&(&dbs_info->work)->work){+.+...}, at: [<c109962a>] wait_on_work+0x0/0xba > [ 144.962016] > [ 144.962016] but task is already holding lock: > [ 144.962016] (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [<c1f5dd3f>] lock_policy_rwsem_write+0x73/0xec > [ 144.962016] > [ 144.962016] which lock already depends on the new lock. > [ 144.962016] > [ 144.962016] > [ 144.962016] the existing dependency chain (in reverse order) is: > [ 144.962016] > [ 144.962016] -> #1 (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}: > [ 144.962016] [<c10bcd0d>] check_prev_add+0xf0/0x151 > [ 144.962016] [<c10bcdd3>] check_prevs_add+0x65/0xbf > [ 144.962016] [<c10bce9e>] validate_chain+0x71/0x99 > [ 144.962016] [<c10bd184>] __lock_acquire+0x2be/0x33d > [ 144.962016] [<c10bd27f>] lock_acquire+0x7c/0x9f > [ 144.962016] [<c23b1b36>] down_write+0x32/0x95 > [ 144.962016] [<c1f5dd3f>] lock_policy_rwsem_write+0x73/0xec > [ 144.962016] [<c1f627cd>] do_dbs_timer+0x50/0x160 > [ 144.962016] [<c1098de1>] run_workqueue+0xec/0x243 > [ 144.962016] [<c109badf>] worker_thread+0x13b/0x14c > [ 144.962016] [<c10a05ed>] kthread+0x89/0x92 > [ 144.962016] [<c10064a7>] kernel_thread_helper+0x7/0x10 > [ 144.962016] [<ffffffff>] 0xffffffff > [ 144.962016] > [ 144.962016] -> #0 (&(&dbs_info->work)->work){+.+...}: > [ 144.962016] [<c10bcc50>] check_prev_add+0x33/0x151 > [ 144.962016] [<c10bcdd3>] check_prevs_add+0x65/0xbf > [ 144.962016] [<c10bce9e>] validate_chain+0x71/0x99 > [ 144.962016] [<c10bd184>] __lock_acquire+0x2be/0x33d > [ 144.962016] [<c10bd27f>] lock_acquire+0x7c/0x9f > [ 144.962016] [<c1099662>] wait_on_work+0x38/0xba > [ 144.962016] [<c109975c>] __cancel_work_timer+0x78/0x99 > [ 144.962016] [<c109978d>] cancel_delayed_work_sync+0x10/0x12 > [ 144.962016] [<c1f62710>] dbs_timer_exit+0x17/0x19 > [ 144.962016] [<c1f62d68>] cpufreq_governor_dbs+0x23f/0x2df > [ 144.962016] [<c1f5e7cb>] __cpufreq_governor+0x9a/0xde > [ 144.962016] [<c1f5ea3c>] __cpufreq_set_policy+0x22d/0x2fa > [ 144.967630] [<c1f5ebce>] store_scaling_governor+0xc5/0x108 > [ 144.967630] [<c1f5e11d>] store+0xa4/0xbd > [ 144.967630] [<c11fa00f>] flush_write_buffer+0x6d/0x81 > [ 144.967630] [<c11fb23f>] sysfs_write_file+0x66/0xa6 > [ 144.967630] [<c11814e0>] vfs_write+0x1ad/0x1f9 > [ 144.967630] [<c1181fc6>] sys_write+0x5e/0x80 > [ 144.967630] [<c100582b>] sysenter_do_call+0x12/0x38 > [ 144.967630] [<ffffffff>] 0xffffffff > [ 144.967630] > [ 144.967630] other info that might help us debug this: > [ 144.967630] > [ 144.967630] 2 locks held by S99local/8461: > [ 144.967630] #0: (&buffer->mutex){+.+.+.}, at: [<c11fb201>] sysfs_write_file+0x28/0xa6 > [ 144.967630] #1: (&per_cpu(cpu_policy_rwsem, cpu)){+++++.}, at: [<c1f5dd3f>] lock_policy_rwsem_write+0x73/0xec > [ 144.967630] > [ 144.967630] stack backtrace: > [ 144.967630] Pid: 8461, comm: S99local Tainted: G W 2.6.30-tip-08973-gb747c8d-dirty #6295 > [ 144.967630] Call Trace: > [ 144.967630] [<c10bb9d8>] print_circular_bug_tail+0x5d/0x68 > [ 144.967630] [<c10bcc50>] check_prev_add+0x33/0x151 > [ 144.967630] [<c10b8974>] ? list_add_tail_rcu+0xd/0xf > [ 144.967630] [<c10bcdd3>] check_prevs_add+0x65/0xbf > [ 144.967630] [<c10bce9e>] validate_chain+0x71/0x99 > [ 144.967630] [<c10bd184>] __lock_acquire+0x2be/0x33d > [ 144.967630] [<c10bd27f>] lock_acquire+0x7c/0x9f > [ 144.967630] [<c109962a>] ? wait_on_work+0x0/0xba > [ 144.967630] [<c1099662>] wait_on_work+0x38/0xba > [ 144.967630] [<c109962a>] ? wait_on_work+0x0/0xba > [ 144.967630] [<c110c292>] ? ftrace_likely_update+0x11/0x22 > [ 144.967630] [<c109975c>] __cancel_work_timer+0x78/0x99 > [ 144.967630] [<c109978d>] cancel_delayed_work_sync+0x10/0x12 > [ 144.967630] [<c1f62710>] dbs_timer_exit+0x17/0x19 > [ 144.967630] [<c1f62d68>] cpufreq_governor_dbs+0x23f/0x2df > [ 144.967630] [<c1f5e7cb>] __cpufreq_governor+0x9a/0xde > [ 144.967630] [<c1f5ea3c>] __cpufreq_set_policy+0x22d/0x2fa > [ 144.967630] [<c1f5ebce>] store_scaling_governor+0xc5/0x108 > [ 144.967630] [<c1f60123>] ? handle_update+0x0/0x2d > [ 144.967630] [<c1f5dd6f>] ? lock_policy_rwsem_write+0xa3/0xec > [ 144.967630] [<c1f5e11d>] store+0xa4/0xbd > [ 144.967630] [<c11fa00f>] flush_write_buffer+0x6d/0x81 > [ 144.967630] [<c11fb23f>] sysfs_write_file+0x66/0xa6 > [ 144.967630] [<c11814e0>] vfs_write+0x1ad/0x1f9 > [ 144.967630] [<c1181fc6>] sys_write+0x5e/0x80 > [ 144.967630] [<c100582b>] sysenter_do_call+0x12/0x38 > [ 146.085749] PM: Adding info for No Bus:vcs4 > [ 146.085864] PM: Adding info for No Bus:vcsa4 > [ 146.090924] PM: Adding info for No Bus:vcs9 > [ 146.091077] PM: Adding info for No Bus:vcsa9 > [ 146.092977] PM: Adding info for No Bus:vcs3 -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
