Applying the patch version 2, i.e. replacing synchronize_rcu() with synchronize_rcu_exhibited in the method acpi_os_map_cleanup() causes a regression in i2c-based touchscreen drivers such that they are not recognized. See https://bugzilla.kernel.org/show_bug.cgi?id=94281. Reverting this modification re-enables the recognition of touchscreens on Dell Venue 11 pro devices at least. If the initial patch from Konstantin Khlebnikov is applied, the touchscreen still works (tested by myself). Hence, I vote for pulling the original patch in, avoiding the regression while still solving the initial problem mentioned on the list. The patch is attached to this mail, again. ----------------------------------------------------- --- drivers/acpi/osl.c.orig 2015-08-02 18:55:35.902306862 +0200 +++ drivers/acpi/osl.c 2015-08-02 12:32:59.845090711 +0200 @@ -94,10 +94,13 @@ acpi_physical_address phys; acpi_size size; unsigned long refcount; + atomic_t active; + struct rcu_head rcu_head; }; static LIST_HEAD(acpi_ioremaps); static DEFINE_MUTEX(acpi_ioremap_lock); +static DECLARE_WAIT_QUEUE_HEAD(acpi_ioremap_wq); static void __init acpi_osi_setup_late(void); @@ -290,17 +293,31 @@ return NULL; } -/* Must be called with 'acpi_ioremap_lock' or RCU read lock held. */ -static void __iomem * -acpi_map_vaddr_lookup(acpi_physical_address phys, unsigned int size) +static void __iomem *acpi_get_ioremap(acpi_physical_address phys, + acpi_size size, struct acpi_ioremap **pmap) { struct acpi_ioremap *map; + rcu_read_lock(); map = acpi_map_lookup(phys, size); - if (map) + if (map && atomic_inc_not_zero(&map->active)) { + rcu_read_unlock(); + *pmap = map; return map->virt + (phys - map->phys); + } + rcu_read_unlock(); - return NULL; + *pmap = NULL; + return acpi_os_ioremap(phys, size); +} + +static void acpi_put_ioremap(void __iomem *virt, struct acpi_ioremap *map) +{ + if (map) { + if (atomic_dec_and_test(&map->active)) + wake_up_all(&acpi_ioremap_wq); + } else + iounmap(virt); } void __iomem *acpi_os_get_iomem(acpi_physical_address phys, unsigned int size) @@ -408,6 +425,7 @@ map->phys = pg_off; map->size = pg_sz; map->refcount = 1; + atomic_set(&map->active, 1); list_add_tail_rcu(&map->list, &acpi_ioremaps); @@ -433,9 +451,10 @@ static void acpi_os_map_cleanup(struct acpi_ioremap *map) { if (!map->refcount) { - synchronize_rcu_exhibited(); + atomic_dec(&map->active); + wait_event(acpi_ioremap_wq, !atomic_read(&map->active)); acpi_unmap(map->phys, map->virt); - kfree(map); + kfree_rcu(map, rcu_head); } } @@ -944,20 +963,14 @@ acpi_status acpi_os_read_memory(acpi_physical_address phys_addr, u64 *value, u32 width) { + struct acpi_ioremap *map; void __iomem *virt_addr; unsigned int size = width / 8; - bool unmap = false; u64 dummy; - rcu_read_lock(); - virt_addr = acpi_map_vaddr_lookup(phys_addr, size); - if (!virt_addr) { - rcu_read_unlock(); - virt_addr = acpi_os_ioremap(phys_addr, size); - if (!virt_addr) - return AE_BAD_ADDRESS; - unmap = true; - } + virt_addr = acpi_get_ioremap(phys_addr, size, &map); + if (!virt_addr) + return AE_BAD_ADDRESS; if (!value) value = &dummy; @@ -979,10 +992,7 @@ BUG(); } - if (unmap) - iounmap(virt_addr); - else - rcu_read_unlock(); + acpi_put_ioremap(virt_addr, map); return AE_OK; } @@ -1003,19 +1013,13 @@ acpi_status acpi_os_write_memory(acpi_physical_address phys_addr, u64 value, u32 width) { + struct acpi_ioremap *map; void __iomem *virt_addr; unsigned int size = width / 8; - bool unmap = false; - rcu_read_lock(); - virt_addr = acpi_map_vaddr_lookup(phys_addr, size); - if (!virt_addr) { - rcu_read_unlock(); - virt_addr = acpi_os_ioremap(phys_addr, size); - if (!virt_addr) - return AE_BAD_ADDRESS; - unmap = true; - } + virt_addr = acpi_get_ioremap(phys_addr, size, &map); + if (!virt_addr) + return AE_BAD_ADDRESS; switch (width) { case 8: @@ -1034,10 +1038,7 @@ BUG(); } - if (unmap) - iounmap(virt_addr); - else - rcu_read_unlock(); + acpi_put_ioremap(virt_addr, map); return AE_OK; } -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
