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Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0053-io-mapping-don-t-disable-preempt-on-RT-in-io_mapping.patch | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/debian/patches-rt/0053-io-mapping-don-t-disable-preempt-on-RT-in-io_mapping.patch b/debian/patches-rt/0053-io-mapping-don-t-disable-preempt-on-RT-in-io_mapping.patch new file mode 100644 index 000000000..b4b695541 --- /dev/null +++ b/debian/patches-rt/0053-io-mapping-don-t-disable-preempt-on-RT-in-io_mapping.patch @@ -0,0 +1,93 @@ +From 53c6a09e670e985d37ca05785a0155ab51b49cf4 Mon Sep 17 00:00:00 2001 +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Fri, 10 Mar 2023 17:29:05 +0100 +Subject: [PATCH 53/62] io-mapping: don't disable preempt on RT in + io_mapping_map_atomic_wc(). +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.1/older/patches-6.1.69-rt21.tar.xz + +io_mapping_map_atomic_wc() disables preemption and pagefaults for +historical reasons. The conversion to io_mapping_map_local_wc(), which +only disables migration, cannot be done wholesale because quite some call +sites need to be updated to accommodate with the changed semantics. + +On PREEMPT_RT enabled kernels the io_mapping_map_atomic_wc() semantics are +problematic due to the implicit disabling of preemption which makes it +impossible to acquire 'sleeping' spinlocks within the mapped atomic +sections. + +PREEMPT_RT replaces the preempt_disable() with a migrate_disable() for +more than a decade. It could be argued that this is a justification to do +this unconditionally, but PREEMPT_RT covers only a limited number of +architectures and it disables some functionality which limits the coverage +further. + +Limit the replacement to PREEMPT_RT for now. This is also done +kmap_atomic(). + +Link: https://lkml.kernel.org/r/20230310162905.O57Pj7hh@linutronix.de +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Reported-by: Richard Weinberger <richard.weinberger@gmail.com> + Link: https://lore.kernel.org/CAFLxGvw0WMxaMqYqJ5WgvVSbKHq2D2xcXTOgMCpgq9nDC-MWTQ@mail.gmail.com +Cc: Thomas Gleixner <tglx@linutronix.de> +Signed-off-by: Andrew Morton <akpm@linux-foundation.org> +(cherry picked from commit 7eb16f23b9a415f062db22739e59bb144e0b24ab) +Signed-off-by: Clark Williams <clark.williams@gmail.com> +--- + include/linux/io-mapping.h | 20 ++++++++++++++++---- + 1 file changed, 16 insertions(+), 4 deletions(-) + +diff --git a/include/linux/io-mapping.h b/include/linux/io-mapping.h +index 66a774d2710e..b08532b8fba7 100644 +--- a/include/linux/io-mapping.h ++++ b/include/linux/io-mapping.h +@@ -69,7 +69,10 @@ io_mapping_map_atomic_wc(struct io_mapping *mapping, + + BUG_ON(offset >= mapping->size); + phys_addr = mapping->base + offset; +- preempt_disable(); ++ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) ++ preempt_disable(); ++ else ++ migrate_disable(); + pagefault_disable(); + return __iomap_local_pfn_prot(PHYS_PFN(phys_addr), mapping->prot); + } +@@ -79,7 +82,10 @@ io_mapping_unmap_atomic(void __iomem *vaddr) + { + kunmap_local_indexed((void __force *)vaddr); + pagefault_enable(); +- preempt_enable(); ++ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) ++ preempt_enable(); ++ else ++ migrate_enable(); + } + + static inline void __iomem * +@@ -162,7 +168,10 @@ static inline void __iomem * + io_mapping_map_atomic_wc(struct io_mapping *mapping, + unsigned long offset) + { +- preempt_disable(); ++ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) ++ preempt_disable(); ++ else ++ migrate_disable(); + pagefault_disable(); + return io_mapping_map_wc(mapping, offset, PAGE_SIZE); + } +@@ -172,7 +181,10 @@ io_mapping_unmap_atomic(void __iomem *vaddr) + { + io_mapping_unmap(vaddr); + pagefault_enable(); +- preempt_enable(); ++ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) ++ preempt_enable(); ++ else ++ migrate_enable(); + } + + static inline void __iomem * +-- +2.43.0 + |