Patch "dma-debug: don't call __dma_entry_alloc_check_leak() under free_entries_lock" has been added to the 5.10-stable tree

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This is a note to let you know that I've just added the patch titled

    dma-debug: don't call __dma_entry_alloc_check_leak() under free_entries_lock

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     dma-debug-don-t-call-__dma_entry_alloc_check_leak-un.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 8c112c813da148846702132619d56b57129bbdb9
Author: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Date:   Wed Aug 16 11:32:21 2023 +0900

    dma-debug: don't call __dma_entry_alloc_check_leak() under free_entries_lock
    
    [ Upstream commit fb5a4315591dae307a65fc246ca80b5159d296e1 ]
    
    __dma_entry_alloc_check_leak() calls into printk -> serial console
    output (qcom geni) and grabs port->lock under free_entries_lock
    spin lock, which is a reverse locking dependency chain as qcom_geni
    IRQ handler can call into dma-debug code and grab free_entries_lock
    under port->lock.
    
    Move __dma_entry_alloc_check_leak() call out of free_entries_lock
    scope so that we don't acquire serial console's port->lock under it.
    
    Trimmed-down lockdep splat:
    
     The existing dependency chain (in reverse order) is:
    
                   -> #2 (free_entries_lock){-.-.}-{2:2}:
            _raw_spin_lock_irqsave+0x60/0x80
            dma_entry_alloc+0x38/0x110
            debug_dma_map_page+0x60/0xf8
            dma_map_page_attrs+0x1e0/0x230
            dma_map_single_attrs.constprop.0+0x6c/0xc8
            geni_se_rx_dma_prep+0x40/0xcc
            qcom_geni_serial_isr+0x310/0x510
            __handle_irq_event_percpu+0x110/0x244
            handle_irq_event_percpu+0x20/0x54
            handle_irq_event+0x50/0x88
            handle_fasteoi_irq+0xa4/0xcc
            handle_irq_desc+0x28/0x40
            generic_handle_domain_irq+0x24/0x30
            gic_handle_irq+0xc4/0x148
            do_interrupt_handler+0xa4/0xb0
            el1_interrupt+0x34/0x64
            el1h_64_irq_handler+0x18/0x24
            el1h_64_irq+0x64/0x68
            arch_local_irq_enable+0x4/0x8
            ____do_softirq+0x18/0x24
            ...
    
                   -> #1 (&port_lock_key){-.-.}-{2:2}:
            _raw_spin_lock_irqsave+0x60/0x80
            qcom_geni_serial_console_write+0x184/0x1dc
            console_flush_all+0x344/0x454
            console_unlock+0x94/0xf0
            vprintk_emit+0x238/0x24c
            vprintk_default+0x3c/0x48
            vprintk+0xb4/0xbc
            _printk+0x68/0x90
            register_console+0x230/0x38c
            uart_add_one_port+0x338/0x494
            qcom_geni_serial_probe+0x390/0x424
            platform_probe+0x70/0xc0
            really_probe+0x148/0x280
            __driver_probe_device+0xfc/0x114
            driver_probe_device+0x44/0x100
            __device_attach_driver+0x64/0xdc
            bus_for_each_drv+0xb0/0xd8
            __device_attach+0xe4/0x140
            device_initial_probe+0x1c/0x28
            bus_probe_device+0x44/0xb0
            device_add+0x538/0x668
            of_device_add+0x44/0x50
            of_platform_device_create_pdata+0x94/0xc8
            of_platform_bus_create+0x270/0x304
            of_platform_populate+0xac/0xc4
            devm_of_platform_populate+0x60/0xac
            geni_se_probe+0x154/0x160
            platform_probe+0x70/0xc0
            ...
    
                   -> #0 (console_owner){-...}-{0:0}:
            __lock_acquire+0xdf8/0x109c
            lock_acquire+0x234/0x284
            console_flush_all+0x330/0x454
            console_unlock+0x94/0xf0
            vprintk_emit+0x238/0x24c
            vprintk_default+0x3c/0x48
            vprintk+0xb4/0xbc
            _printk+0x68/0x90
            dma_entry_alloc+0xb4/0x110
            debug_dma_map_sg+0xdc/0x2f8
            __dma_map_sg_attrs+0xac/0xe4
            dma_map_sgtable+0x30/0x4c
            get_pages+0x1d4/0x1e4 [msm]
            msm_gem_pin_pages_locked+0x38/0xac [msm]
            msm_gem_pin_vma_locked+0x58/0x88 [msm]
            msm_ioctl_gem_submit+0xde4/0x13ac [msm]
            drm_ioctl_kernel+0xe0/0x15c
            drm_ioctl+0x2e8/0x3f4
            vfs_ioctl+0x30/0x50
            ...
    
     Chain exists of:
       console_owner --> &port_lock_key --> free_entries_lock
    
      Possible unsafe locking scenario:
    
            CPU0                    CPU1
            ----                    ----
       lock(free_entries_lock);
                                    lock(&port_lock_key);
                                    lock(free_entries_lock);
       lock(console_owner);
    
                    *** DEADLOCK ***
    
     Call trace:
      dump_backtrace+0xb4/0xf0
      show_stack+0x20/0x30
      dump_stack_lvl+0x60/0x84
      dump_stack+0x18/0x24
      print_circular_bug+0x1cc/0x234
      check_noncircular+0x78/0xac
      __lock_acquire+0xdf8/0x109c
      lock_acquire+0x234/0x284
      console_flush_all+0x330/0x454
      console_unlock+0x94/0xf0
      vprintk_emit+0x238/0x24c
      vprintk_default+0x3c/0x48
      vprintk+0xb4/0xbc
      _printk+0x68/0x90
      dma_entry_alloc+0xb4/0x110
      debug_dma_map_sg+0xdc/0x2f8
      __dma_map_sg_attrs+0xac/0xe4
      dma_map_sgtable+0x30/0x4c
      get_pages+0x1d4/0x1e4 [msm]
      msm_gem_pin_pages_locked+0x38/0xac [msm]
      msm_gem_pin_vma_locked+0x58/0x88 [msm]
      msm_ioctl_gem_submit+0xde4/0x13ac [msm]
      drm_ioctl_kernel+0xe0/0x15c
      drm_ioctl+0x2e8/0x3f4
      vfs_ioctl+0x30/0x50
      ...
    
    Reported-by: Rob Clark <robdclark@xxxxxxxxxxxx>
    Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
    Acked-by: Robin Murphy <robin.murphy@xxxxxxx>
    Signed-off-by: Christoph Hellwig <hch@xxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index ae9fc1ee6d206..0263983089097 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -606,15 +606,19 @@ static struct dma_debug_entry *__dma_entry_alloc(void)
 	return entry;
 }
 
-static void __dma_entry_alloc_check_leak(void)
+/*
+ * This should be called outside of free_entries_lock scope to avoid potential
+ * deadlocks with serial consoles that use DMA.
+ */
+static void __dma_entry_alloc_check_leak(u32 nr_entries)
 {
-	u32 tmp = nr_total_entries % nr_prealloc_entries;
+	u32 tmp = nr_entries % nr_prealloc_entries;
 
 	/* Shout each time we tick over some multiple of the initial pool */
 	if (tmp < DMA_DEBUG_DYNAMIC_ENTRIES) {
 		pr_info("dma_debug_entry pool grown to %u (%u00%%)\n",
-			nr_total_entries,
-			(nr_total_entries / nr_prealloc_entries));
+			nr_entries,
+			(nr_entries / nr_prealloc_entries));
 	}
 }
 
@@ -625,8 +629,10 @@ static void __dma_entry_alloc_check_leak(void)
  */
 static struct dma_debug_entry *dma_entry_alloc(void)
 {
+	bool alloc_check_leak = false;
 	struct dma_debug_entry *entry;
 	unsigned long flags;
+	u32 nr_entries;
 
 	spin_lock_irqsave(&free_entries_lock, flags);
 	if (num_free_entries == 0) {
@@ -636,13 +642,17 @@ static struct dma_debug_entry *dma_entry_alloc(void)
 			pr_err("debugging out of memory - disabling\n");
 			return NULL;
 		}
-		__dma_entry_alloc_check_leak();
+		alloc_check_leak = true;
+		nr_entries = nr_total_entries;
 	}
 
 	entry = __dma_entry_alloc();
 
 	spin_unlock_irqrestore(&free_entries_lock, flags);
 
+	if (alloc_check_leak)
+		__dma_entry_alloc_check_leak(nr_entries);
+
 #ifdef CONFIG_STACKTRACE
 	entry->stack_len = stack_trace_save(entry->stack_entries,
 					    ARRAY_SIZE(entry->stack_entries),



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