diff options
Diffstat (limited to 'Documentation/core-api')
| -rw-r--r-- | Documentation/core-api/cpu_hotplug.rst | 2 | ||||
| -rw-r--r-- | Documentation/core-api/packing.rst | 71 | ||||
| -rw-r--r-- | Documentation/core-api/printk-formats.rst | 20 | ||||
| -rw-r--r-- | Documentation/core-api/swiotlb.rst | 4 | ||||
| -rw-r--r-- | Documentation/core-api/workqueue.rst | 9 |
5 files changed, 100 insertions, 6 deletions
diff --git a/Documentation/core-api/cpu_hotplug.rst b/Documentation/core-api/cpu_hotplug.rst index a21dbf261be7..e1b0eeabbb5e 100644 --- a/Documentation/core-api/cpu_hotplug.rst +++ b/Documentation/core-api/cpu_hotplug.rst @@ -616,7 +616,7 @@ ONLINE section for notifications on online and offline operation:: .... cpuhp_remove_instance(state, &inst2->node); .... - remove_multi_state(state); + cpuhp_remove_multi_state(state); Testing of hotplug states diff --git a/Documentation/core-api/packing.rst b/Documentation/core-api/packing.rst index 3ed13bc9a195..821691f23c54 100644 --- a/Documentation/core-api/packing.rst +++ b/Documentation/core-api/packing.rst @@ -151,6 +151,77 @@ the more significant 4-byte word. We always think of our offsets as if there were no quirk, and we translate them afterwards, before accessing the memory region. +Note on buffer lengths not multiple of 4 +---------------------------------------- + +To deal with memory layout quirks where groups of 4 bytes are laid out "little +endian" relative to each other, but "big endian" within the group itself, the +concept of groups of 4 bytes is intrinsic to the packing API (not to be +confused with the memory access, which is performed byte by byte, though). + +With buffer lengths not multiple of 4, this means one group will be incomplete. +Depending on the quirks, this may lead to discontinuities in the bit fields +accessible through the buffer. The packing API assumes discontinuities were not +the intention of the memory layout, so it avoids them by effectively logically +shortening the most significant group of 4 octets to the number of octets +actually available. + +Example with a 31 byte sized buffer given below. Physical buffer offsets are +implicit, and increase from left to right within a group, and from top to +bottom within a column. + +No quirks: + +:: + + 31 29 28 | Group 7 (most significant) + 27 26 25 24 | Group 6 + 23 22 21 20 | Group 5 + 19 18 17 16 | Group 4 + 15 14 13 12 | Group 3 + 11 10 9 8 | Group 2 + 7 6 5 4 | Group 1 + 3 2 1 0 | Group 0 (least significant) + +QUIRK_LSW32_IS_FIRST: + +:: + + 3 2 1 0 | Group 0 (least significant) + 7 6 5 4 | Group 1 + 11 10 9 8 | Group 2 + 15 14 13 12 | Group 3 + 19 18 17 16 | Group 4 + 23 22 21 20 | Group 5 + 27 26 25 24 | Group 6 + 30 29 28 | Group 7 (most significant) + +QUIRK_LITTLE_ENDIAN: + +:: + + 30 28 29 | Group 7 (most significant) + 24 25 26 27 | Group 6 + 20 21 22 23 | Group 5 + 16 17 18 19 | Group 4 + 12 13 14 15 | Group 3 + 8 9 10 11 | Group 2 + 4 5 6 7 | Group 1 + 0 1 2 3 | Group 0 (least significant) + +QUIRK_LITTLE_ENDIAN | QUIRK_LSW32_IS_FIRST: + +:: + + 0 1 2 3 | Group 0 (least significant) + 4 5 6 7 | Group 1 + 8 9 10 11 | Group 2 + 12 13 14 15 | Group 3 + 16 17 18 19 | Group 4 + 20 21 22 23 | Group 5 + 24 25 26 27 | Group 6 + 28 29 30 | Group 7 (most significant) + Intended use ------------ diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index 14e093da3ccd..ecccc0473da9 100644 --- a/Documentation/core-api/printk-formats.rst +++ b/Documentation/core-api/printk-formats.rst @@ -209,12 +209,17 @@ Struct Resources :: %pr [mem 0x60000000-0x6fffffff flags 0x2200] or + [mem 0x60000000 flags 0x2200] or [mem 0x0000000060000000-0x000000006fffffff flags 0x2200] + [mem 0x0000000060000000 flags 0x2200] %pR [mem 0x60000000-0x6fffffff pref] or + [mem 0x60000000 pref] or [mem 0x0000000060000000-0x000000006fffffff pref] + [mem 0x0000000060000000 pref] For printing struct resources. The ``R`` and ``r`` specifiers result in a -printed resource with (R) or without (r) a decoded flags member. +printed resource with (R) or without (r) a decoded flags member. If start is +equal to end only print the start value. Passed by reference. @@ -231,6 +236,19 @@ width of the CPU data path. Passed by reference. +Struct Range +------------ + +:: + + %pra [range 0x0000000060000000-0x000000006fffffff] or + [range 0x0000000060000000] + +For printing struct range. struct range holds an arbitrary range of u64 +values. If start is equal to end only print the start value. + +Passed by reference. + DMA address types dma_addr_t ---------------------------- diff --git a/Documentation/core-api/swiotlb.rst b/Documentation/core-api/swiotlb.rst index cf06bae44ff8..9e0fe027dd3b 100644 --- a/Documentation/core-api/swiotlb.rst +++ b/Documentation/core-api/swiotlb.rst @@ -295,9 +295,9 @@ slot set. Fourth, the io_tlb_slot array keeps track of any "padding slots" allocated to meet alloc_align_mask requirements described above. When -swiotlb_tlb_map_single() allocates bounce buffer space to meet alloc_align_mask +swiotlb_tbl_map_single() allocates bounce buffer space to meet alloc_align_mask requirements, it may allocate pre-padding space across zero or more slots. But -when swiotbl_tlb_unmap_single() is called with the bounce buffer address, the +when swiotlb_tbl_unmap_single() is called with the bounce buffer address, the alloc_align_mask value that governed the allocation, and therefore the allocation of any padding slots, is not known. The "pad_slots" field records the number of padding slots so that swiotlb_tbl_unmap_single() can free them. diff --git a/Documentation/core-api/workqueue.rst b/Documentation/core-api/workqueue.rst index 16f861c9791e..e295835fc116 100644 --- a/Documentation/core-api/workqueue.rst +++ b/Documentation/core-api/workqueue.rst @@ -245,8 +245,8 @@ CPU which can be assigned to the work items of a wq. For example, with at the same time per CPU. This is always a per-CPU attribute, even for unbound workqueues. -The maximum limit for ``@max_active`` is 512 and the default value used -when 0 is specified is 256. These values are chosen sufficiently high +The maximum limit for ``@max_active`` is 2048 and the default value used +when 0 is specified is 1024. These values are chosen sufficiently high such that they are not the limiting factor while providing protection in runaway cases. @@ -357,6 +357,11 @@ Guidelines difference in execution characteristics between using a dedicated wq and a system wq. + Note: If something may generate more than @max_active outstanding + work items (do stress test your producers), it may saturate a system + wq and potentially lead to deadlock. It should utilize its own + dedicated workqueue rather than the system wq. + * Unless work items are expected to consume a huge amount of CPU cycles, using a bound wq is usually beneficial due to the increased level of locality in wq operations and work item execution. |