This patch is used to fix the panic issue of parallel device removal on different pci hierarchy, refer to https://bugzilla.kernel.org/show_bug.cgi?id=54411. [ 418.775140] ioatdma i7core_edac edac_core sg e1000e igb dca ptp pps_core sd_mod crc_t10dif megaraid_sas mptsas mptscsih mptbase scsi_transport_sas scsi_mod [ 418.946462] CPU 4 [ 418.968377] Pid: 512, comm: kworker/u:2 Tainted: G W 3.8.0 #2 FUJITSU-SV PRIMEQUEST 1800E/SB [ 419.081763] RIP: 0010:[<ffffffff8137972e>] [<ffffffff8137972e>] pci_bus_read_config_word+0x5e/0x90 [ 419.189965] RSP: 0018:ffff8807b0a37c08 EFLAGS: 00010046 [ 419.253409] RAX: 6b6b6b6b6b6b6b6b RBX: ffff8807bb4a1290 RCX: 0000000000000002 [ 419.338658] RDX: 00000000000000c4 RSI: 0000000000000008 RDI: ffff8807bb4a1290 [ 419.423925] RBP: ffff8807b0a37c48 R08: ffff8807b0a37c24 R09: 6db5c22da55960d0 [ 419.509175] R10: 0000000000000000 R11: 000000000003ecd0 R12: ffff8807b0a37c66 [ 419.594425] R13: 0000000000000282 R14: ffffffff82126d40 R15: 0000000000000000 [ 419.679675] FS: 0000000000000000(0000) GS:ffff8807c2200000(0000) knlGS:0000000000000000 [ 419.776343] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 419.844981] CR2: 00007ffa898a54f8 CR3: 0000000001c0c000 CR4: 00000000000007e0 [ 419.930236] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 420.015484] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [ 420.100736] Process kworker/u:2 (pid: 512, threadinfo ffff8807b0a36000, task ffff8807b30bcd00) [ 420.203632] Stack: [ 420.227623] ffff8807000000c4 ffffffff00000008 ffffffff813851ef 0000000000992000 [ 420.316421] ffff8807b0a37c98 ffff8807bb49b3d8 0000000000000000 0000000000000000 [ 420.405233] ffff8807b0a37c88 ffffffff8138044b ffff8807b0a37c88 0000000000000246 [ 420.494137] Call Trace: [ 420.523326] [<ffffffff813851ef>] ? remove_callback+0x1f/0x40 [ 420.591984] [<ffffffff8138044b>] pci_pme_active+0x4b/0x1c0 [ 420.658545] [<ffffffff8137d8e7>] pci_stop_bus_device+0x57/0xb0 [ 420.729259] [<ffffffff8137dab6>] pci_stop_and_remove_bus_device+0x16/0x30 [ 420.811392] [<ffffffff813851fb>] remove_callback+0x2b/0x40 [ 420.877955] [<ffffffff81257a56>] sysfs_schedule_callback_work+0x26/0x70 [ 420.958017] [<ffffffff810919ae>] process_one_work+0x20e/0x5c0 [ 421.027691] [<ffffffff8109193f>] ? process_one_work+0x19f/0x5c0 [ 421.099441] [<ffffffff81257a30>] ? sysfs_schedule_callback+0x210/0x210 [ 421.178461] [<ffffffff81093a4e>] worker_thread+0x12e/0x370 [ 421.245020] [<ffffffff81093920>] ? manage_workers+0x180/0x180 [ 421.314697] [<ffffffff81099b8e>] kthread+0xee/0x100 [ 421.373992] [<ffffffff810e0f09>] ? __lock_release+0x129/0x190 [ 421.443671] [<ffffffff81099aa0>] ? __init_kthread_worker+0x70/0x70 [ 421.518544] [<ffffffff816b2dac>] ret_from_fork+0x7c/0xb0 [ 421.583031] [<ffffffff81099aa0>] ? __init_kthread_worker+0x70/0x70 [ 421.657894] Code: 89 75 c8 c7 45 dc 00 00 00 00 e8 4e ef 32 00 49 89 c5 48 8b 83 b8 00 00 00 4c 8d 45 dc b9 02 00 00 00 8b 55 c0 8b 75 c8 48 89 df <ff> 10 8b 55 dc 4c 89 ee 48 c7 c7 c0 67 cb 81 89 45 c8 66 41 89 [ 421.890306] RIP [<ffffffff8137972e>] pci_bus_read_config_word+0x5e/0x90 [ 421.970475] RSP <ffff8807b0a37c08> [ 422.012121] ---[ end trace 403f76cf31f1bcb1 ]--- It is easy to reproduce with the following script: echo -n 1 > /sys/bus/pci/devices/0000\:10\:00.0/remove ; echo -n 1 > /sys/bus/pci/devices/0000\:1a\:01.0/remove The 1a:01.0 device is downstream from the 10:00.0 bridge. The sysfs interface remove_store() uses device_schedule_callback() to schedule the remove for later. What's happening is that we schedule remove_callback() for both devices before 10:00.0 has been removed, like this: # echo -n 1 > /sys/bus/pci/devices/0000\:10\:00.0/remove remove_store # for 10:00.0 device_schedule_callback(10:00.0, remove_callback) sysfs_schedule_callback kobject_get queue_work # echo -n 1 > /sys/bus/pci/devices/0000\:1a\:01.0/remove remove_store # for 1a:01.0 device_schedule_callback(1a:01.0, remove_callback) sysfs_schedule_callback kobject_get queue_work Later, we run the callbacks, starting with 10:00.0. This calls remove_callback() to perform the remove: remove_callback(10:00.0) mutex_lock(&pci_remove_rescan_mutex) pci_stop_and_remove_bus_device(pdev) mutex_unlock(&pci_remove_rescan_mutex) This will stop and remove the subtree below 10:00.0, but it does not actually free the pci_dev for 1a:01.0 because we increased its ref count in sysfs_schedule_callback. So after completing remove_callback(10:00.0), we run the second callback for 1a:01.0. But the PCI core did this removal wrong. It deallocated the struct pci_bus for bus 0000:1a too soon. So we add the pci bus' reference management, take a reference on the bus object when capturing the struct pci_bus pointer, in order to keep it valid as long as the pci_dev exists. And check if the device get removed from pci tree already in the protection under pci_remove_rescan_mutex in remove_callback() before we call pci_stop_and_remove_bus_device() to do the removal job. v2: 1.Rework the patchset on Yinghai's patch: [PATCH -v3] PCI: Fix racing for pci device removing via sysfs 2.Follow Bjorn's correction to move pci_bus_put() to pci_release_dev() instead. 3.Follow Jiang's suggestion to split pci_bus_get()/pci_bus_put() into a single patch. Gu Zheng (4): PCI: Introduce pci_alloc_dev(struct pci_bus*) to replace alloc_pci_dev() PCI: introduce pci_bus_get()/pci_bus_put() to hide pci_bus' reference management PCI: Convert alloc_pci_dev(void) to pci_alloc_dev(bus) instead PCI: Fix racing for pci device removing via sysfs arch/powerpc/kernel/pci_of_scan.c | 3 +-- arch/sparc/kernel/pci.c | 3 +-- drivers/char/agp/alpha-agp.c | 2 +- drivers/char/agp/parisc-agp.c | 2 +- drivers/pci/bus.c | 15 +++++++++++++++ drivers/pci/iov.c | 8 +++++--- drivers/pci/pci-sysfs.c | 13 ++++++++++--- drivers/pci/probe.c | 15 ++++++++++++--- drivers/scsi/megaraid.c | 2 +- include/linux/pci.h | 7 ++++++- 10 files changed, 53 insertions(+), 17 deletions(-) -- 1.7.7 -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
