diff options
Diffstat (limited to 'debian/patches-rt/0030-highmem-Make-DEBUG_HIGHMEM-functional.patch')
| -rw-r--r-- | debian/patches-rt/0030-highmem-Make-DEBUG_HIGHMEM-functional.patch | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/debian/patches-rt/0030-highmem-Make-DEBUG_HIGHMEM-functional.patch b/debian/patches-rt/0030-highmem-Make-DEBUG_HIGHMEM-functional.patch new file mode 100644 index 000000000..139157832 --- /dev/null +++ b/debian/patches-rt/0030-highmem-Make-DEBUG_HIGHMEM-functional.patch @@ -0,0 +1,61 @@ +From 4c9348bc5b225c2de1552b059787335345d30d2c Mon Sep 17 00:00:00 2001 +From: Thomas Gleixner <tglx@linutronix.de> +Date: Tue, 3 Nov 2020 10:27:19 +0100 +Subject: [PATCH 030/323] highmem: Make DEBUG_HIGHMEM functional +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz + +For some obscure reason when CONFIG_DEBUG_HIGHMEM is enabled the stack +depth is increased from 20 to 41. But the only thing DEBUG_HIGHMEM does is +to enable a few BUG_ON()'s in the mapping code. + +That's a leftover from the historical mapping code which had fixed entries +for various purposes. DEBUG_HIGHMEM inserted guard mappings between the map +types. But that got all ditched when kmap_atomic() switched to a stack +based map management. Though the WITH_KM_FENCE magic survived without being +functional. All the thing does today is to increase the stack depth. + +Add a working implementation to the generic kmap_local* implementation. + +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + mm/highmem.c | 14 ++++++++++++-- + 1 file changed, 12 insertions(+), 2 deletions(-) + +diff --git a/mm/highmem.c b/mm/highmem.c +index bb4ce13ee7e7..67d2d5983cb0 100644 +--- a/mm/highmem.c ++++ b/mm/highmem.c +@@ -376,9 +376,19 @@ EXPORT_SYMBOL(kunmap_high); + + static DEFINE_PER_CPU(int, __kmap_local_idx); + ++/* ++ * With DEBUG_HIGHMEM the stack depth is doubled and every second ++ * slot is unused which acts as a guard page ++ */ ++#ifdef CONFIG_DEBUG_HIGHMEM ++# define KM_INCR 2 ++#else ++# define KM_INCR 1 ++#endif ++ + static inline int kmap_local_idx_push(void) + { +- int idx = __this_cpu_inc_return(__kmap_local_idx) - 1; ++ int idx = __this_cpu_add_return(__kmap_local_idx, KM_INCR) - 1; + + WARN_ON_ONCE(in_irq() && !irqs_disabled()); + BUG_ON(idx >= KM_MAX_IDX); +@@ -392,7 +402,7 @@ static inline int kmap_local_idx(void) + + static inline void kmap_local_idx_pop(void) + { +- int idx = __this_cpu_dec_return(__kmap_local_idx); ++ int idx = __this_cpu_sub_return(__kmap_local_idx, KM_INCR); + + BUG_ON(idx < 0); + } +-- +2.43.0 + |