From 5efbabe09d986f25c02d19954660238fcd7f008a Mon Sep 17 00:00:00 2001 From: Gavin Shan Date: Mon, 11 Aug 2014 19:16:20 +1000 Subject: [PATCH] powerpc/pseries: Avoid deadlock on removing ddw Function remove_ddw() could be called in of_reconfig_notifier and we potentially remove the dynamic DMA window property, which invokes of_reconfig_notifier again. Eventually, it leads to the deadlock as following backtrace shows. The patch fixes the above issue by deferring releasing the dynamic DMA window property while releasing the device node. ============================================= [ INFO: possible recursive locking detected ] 3.16.0+ #428 Tainted: G W --------------------------------------------- drmgr/2273 is trying to acquire lock: ((of_reconfig_chain).rwsem){.+.+..}, at: [] \ .__blocking_notifier_call_chain+0x40/0x78 but task is already holding lock: ((of_reconfig_chain).rwsem){.+.+..}, at: [] \ .__blocking_notifier_call_chain+0x40/0x78 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock((of_reconfig_chain).rwsem); lock((of_reconfig_chain).rwsem); *** DEADLOCK *** May be due to missing lock nesting notation 2 locks held by drmgr/2273: #0: (sb_writers#4){.+.+.+}, at: [] \ .vfs_write+0xb0/0x1f8 #1: ((of_reconfig_chain).rwsem){.+.+..}, at: [] \ .__blocking_notifier_call_chain+0x40/0x78 stack backtrace: CPU: 17 PID: 2273 Comm: drmgr Tainted: G W 3.16.0+ #428 Call Trace: [c0000000137e7000] [c000000000013d9c] .show_stack+0x88/0x148 (unreliable) [c0000000137e70b0] [c00000000083cd34] .dump_stack+0x7c/0x9c [c0000000137e7130] [c0000000000b8afc] .__lock_acquire+0x128c/0x1c68 [c0000000137e7280] [c0000000000b9a4c] .lock_acquire+0xe8/0x104 [c0000000137e7350] [c00000000083588c] .down_read+0x4c/0x90 [c0000000137e73e0] [c000000000091890] .__blocking_notifier_call_chain+0x40/0x78 [c0000000137e7490] [c000000000091900] .blocking_notifier_call_chain+0x38/0x48 [c0000000137e7520] [c000000000682a28] .of_reconfig_notify+0x34/0x5c [c0000000137e75b0] [c000000000682a9c] .of_property_notify+0x4c/0x54 [c0000000137e7650] [c000000000682bf0] .of_remove_property+0x30/0xd4 [c0000000137e76f0] [c000000000052a44] .remove_ddw+0x144/0x168 [c0000000137e7790] [c000000000053204] .iommu_reconfig_notifier+0x30/0xe0 [c0000000137e7820] [c00000000009137c] .notifier_call_chain+0x6c/0xb4 [c0000000137e78c0] [c0000000000918ac] .__blocking_notifier_call_chain+0x5c/0x78 [c0000000137e7970] [c000000000091900] .blocking_notifier_call_chain+0x38/0x48 [c0000000137e7a00] [c000000000682a28] .of_reconfig_notify+0x34/0x5c [c0000000137e7a90] [c000000000682e14] .of_detach_node+0x44/0x1fc [c0000000137e7b40] [c0000000000518e4] .ofdt_write+0x3ac/0x688 [c0000000137e7c20] [c000000000238430] .proc_reg_write+0xb8/0xd4 [c0000000137e7cd0] [c0000000001cbeac] .vfs_write+0xec/0x1f8 [c0000000137e7d70] [c0000000001cc3b0] .SyS_write+0x58/0xa0 [c0000000137e7e30] [c00000000000a064] syscall_exit+0x0/0x98 Cc: stable@vger.kernel.org Signed-off-by: Gavin Shan Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/platforms/pseries/iommu.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c index 33b552ffbe57..4642d6a4d356 100644 --- a/arch/powerpc/platforms/pseries/iommu.c +++ b/arch/powerpc/platforms/pseries/iommu.c @@ -721,13 +721,13 @@ static int __init disable_ddw_setup(char *str) early_param("disable_ddw", disable_ddw_setup); -static void remove_ddw(struct device_node *np) +static void remove_ddw(struct device_node *np, bool remove_prop) { struct dynamic_dma_window_prop *dwp; struct property *win64; const u32 *ddw_avail; u64 liobn; - int len, ret; + int len, ret = 0; ddw_avail = of_get_property(np, "ibm,ddw-applicable", &len); win64 = of_find_property(np, DIRECT64_PROPNAME, NULL); @@ -761,7 +761,8 @@ static void remove_ddw(struct device_node *np) np->full_name, ret, ddw_avail[2], liobn); delprop: - ret = of_remove_property(np, win64); + if (remove_prop) + ret = of_remove_property(np, win64); if (ret) pr_warning("%s: failed to remove direct window property: %d\n", np->full_name, ret); @@ -805,7 +806,7 @@ static int find_existing_ddw_windows(void) window = kzalloc(sizeof(*window), GFP_KERNEL); if (!window || len < sizeof(struct dynamic_dma_window_prop)) { kfree(window); - remove_ddw(pdn); + remove_ddw(pdn, true); continue; } @@ -1045,7 +1046,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) kfree(window); out_clear_window: - remove_ddw(pdn); + remove_ddw(pdn, true); out_free_prop: kfree(win64->name); @@ -1255,7 +1256,14 @@ static int iommu_reconfig_notifier(struct notifier_block *nb, unsigned long acti switch (action) { case OF_RECONFIG_DETACH_NODE: - remove_ddw(np); + /* + * Removing the property will invoke the reconfig + * notifier again, which causes dead-lock on the + * read-write semaphore of the notifier chain. So + * we have to remove the property when releasing + * the device node. + */ + remove_ddw(np, false); if (pci && pci->iommu_table) iommu_free_table(pci->iommu_table, np->full_name);