* Russell King (Oracle) <linux@xxxxxxxxxxxxxxx>: > On Tue, May 23, 2023 at 12:24:04PM +0200, Helge Deller wrote: > > On 5/22/23 23:22, Helge Deller wrote: > > > > > It hangs in fs/aio.c:1128, function aio_complete(), in this call: > > > > > spin_lock_irqsave(&ctx->completion_lock, flags); > > > > > > > > All code that I found and that obtains ctx->completion_lock disables IRQs. > > > > It is not clear to me how this spinlock can be locked recursively? Is it > > > > sure that the "spinlock recursion" report is correct? > > > > > > Yes, it seems correct. > > > [...] > > > > Bart, thanks to your suggestions I was able to narrow down the problem! > > > > I got LOCKDEP working on parisc, which then reports: > > raw_local_irq_restore() called with IRQs enabled > > for the spin_unlock_irqrestore() in function aio_complete(), which shouldn't happen. > > > > Finally, I found that parisc's flush_dcache_page() re-enables the IRQs > > which leads to the spinlock hang in aio_complete(). > > > > So, this is NOT a bug in aio or scsci, but we need fix in the the arch code. > > You can find some of the background to this at: > > https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=16ceff2d5dc9f0347ab5a08abff3f4647c2fee04 > > which introduced flush_dcache_mmap_lock(). It looks like Hugh had > questions over whether this should be _irqsave() rather than _irq() > but I guess at the time all callers had interrupts enabled, and > it's only recently that someone came up with the idea of calling > flush_dcache_page() with interrupts disabled. > > Adding another arg to flush_dcache_mmap_lock() to save the flags > may be doable, but requires a patch that touches not only architectures > that have a private implementation, but also various code in mm/. I've tested the attached patch on parisc, and it solves the issue. I've not compile-tested it on arm and nios2, both seem to be the only other affected platforms. Thoughts? Helge >From 25a96a4211975d46e6f4dac06e144d0fb9f5ed53 Mon Sep 17 00:00:00 2001 From: Helge Deller <deller@xxxxxx> Date: Tue, 23 May 2023 21:48:33 +0200 Subject: [PATCH] Fix flush_dcache_page() for usage in irq context flush_dcache_page() can be called with IRQs disabled, e.g. from aio_complete(). Fix flush_dcache_page() on the arm, parisc and nios2 architectures to not unintentionally re-enable IRQs by using xa_lock_irqsave() instead of xa_lock_irq() for the flush_dcache_mmap_*lock() functions. Cc: Russell King (Oracle) <linux@xxxxxxxxxxxxxxx> Cc: Dinh Nguyen <dinguyen@xxxxxxxxxx> Signed-off-by: Helge Deller <deller@xxxxxx> diff --git a/arch/arm/include/asm/cacheflush.h b/arch/arm/include/asm/cacheflush.h index a094f964c869..5b8a1ef0dc50 100644 --- a/arch/arm/include/asm/cacheflush.h +++ b/arch/arm/include/asm/cacheflush.h @@ -315,6 +315,10 @@ static inline void flush_anon_page(struct vm_area_struct *vma, #define flush_dcache_mmap_lock(mapping) xa_lock_irq(&mapping->i_pages) #define flush_dcache_mmap_unlock(mapping) xa_unlock_irq(&mapping->i_pages) +#define flush_dcache_mmap_lock_irqsave(mapping, flags) \ + xa_lock_irqsave(&mapping->i_pages, flags) +#define flush_dcache_mmap_unlock_irqrestore(mapping, flags) \ + xa_unlock_irqrestore(&mapping->i_pages, flags) /* * We don't appear to need to do anything here. In fact, if we did, we'd diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c index 7ff9feea13a6..d57ec9165520 100644 --- a/arch/arm/mm/flush.c +++ b/arch/arm/mm/flush.c @@ -238,6 +238,7 @@ static void __flush_dcache_aliases(struct address_space *mapping, struct page *p { struct mm_struct *mm = current->active_mm; struct vm_area_struct *mpnt; + unsigned long flags; pgoff_t pgoff; /* @@ -248,7 +249,7 @@ static void __flush_dcache_aliases(struct address_space *mapping, struct page *p */ pgoff = page->index; - flush_dcache_mmap_lock(mapping); + flush_dcache_mmap_lock_irqsave(mapping, flags); vma_interval_tree_foreach(mpnt, &mapping->i_mmap, pgoff, pgoff) { unsigned long offset; @@ -262,7 +263,7 @@ static void __flush_dcache_aliases(struct address_space *mapping, struct page *p offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT; flush_cache_page(mpnt, mpnt->vm_start + offset, page_to_pfn(page)); } - flush_dcache_mmap_unlock(mapping); + flush_dcache_mmap_unlock_irqrestore(mapping, flags); } #if __LINUX_ARM_ARCH__ >= 6 diff --git a/arch/nios2/include/asm/cacheflush.h b/arch/nios2/include/asm/cacheflush.h index d0b71dd71287..a37242662809 100644 --- a/arch/nios2/include/asm/cacheflush.h +++ b/arch/nios2/include/asm/cacheflush.h @@ -48,5 +48,9 @@ extern void invalidate_dcache_range(unsigned long start, unsigned long end); #define flush_dcache_mmap_lock(mapping) xa_lock_irq(&mapping->i_pages) #define flush_dcache_mmap_unlock(mapping) xa_unlock_irq(&mapping->i_pages) +#define flush_dcache_mmap_lock_irqsave(mapping, flags) \ + xa_lock_irqsave(&mapping->i_pages, flags) +#define flush_dcache_mmap_unlock_irqrestore(mapping, flags) \ + xa_unlock_irqrestore(&mapping->i_pages, flags) #endif /* _ASM_NIOS2_CACHEFLUSH_H */ diff --git a/arch/nios2/mm/cacheflush.c b/arch/nios2/mm/cacheflush.c index 6aa9257c3ede..35f3b599187f 100644 --- a/arch/nios2/mm/cacheflush.c +++ b/arch/nios2/mm/cacheflush.c @@ -75,11 +75,12 @@ static void flush_aliases(struct address_space *mapping, struct page *page) { struct mm_struct *mm = current->active_mm; struct vm_area_struct *mpnt; + unsigned long flags; pgoff_t pgoff; pgoff = page->index; - flush_dcache_mmap_lock(mapping); + flush_dcache_mmap_lock_irqsave(mapping, flags); vma_interval_tree_foreach(mpnt, &mapping->i_mmap, pgoff, pgoff) { unsigned long offset; @@ -92,7 +93,7 @@ static void flush_aliases(struct address_space *mapping, struct page *page) flush_cache_page(mpnt, mpnt->vm_start + offset, page_to_pfn(page)); } - flush_dcache_mmap_unlock(mapping); + flush_dcache_mmap_unlock_irqrestore(mapping, flags); } void flush_cache_all(void) diff --git a/arch/parisc/include/asm/cacheflush.h b/arch/parisc/include/asm/cacheflush.h index 0bdee6724132..c8b6928cee1e 100644 --- a/arch/parisc/include/asm/cacheflush.h +++ b/arch/parisc/include/asm/cacheflush.h @@ -48,6 +48,10 @@ void flush_dcache_page(struct page *page); #define flush_dcache_mmap_lock(mapping) xa_lock_irq(&mapping->i_pages) #define flush_dcache_mmap_unlock(mapping) xa_unlock_irq(&mapping->i_pages) +#define flush_dcache_mmap_lock_irqsave(mapping, flags) \ + xa_lock_irqsave(&mapping->i_pages, flags) +#define flush_dcache_mmap_unlock_irqrestore(mapping, flags) \ + xa_unlock_irqrestore(&mapping->i_pages, flags) #define flush_icache_page(vma,page) do { \ flush_kernel_dcache_page_addr(page_address(page)); \ diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c index 1d3b8bc8a623..ca4a302d4365 100644 --- a/arch/parisc/kernel/cache.c +++ b/arch/parisc/kernel/cache.c @@ -399,6 +399,7 @@ void flush_dcache_page(struct page *page) unsigned long offset; unsigned long addr, old_addr = 0; unsigned long count = 0; + unsigned long flags; pgoff_t pgoff; if (mapping && !mapping_mapped(mapping)) { @@ -420,7 +421,7 @@ void flush_dcache_page(struct page *page) * to flush one address here for them all to become coherent * on machines that support equivalent aliasing */ - flush_dcache_mmap_lock(mapping); + flush_dcache_mmap_lock_irqsave(mapping, flags); vma_interval_tree_foreach(mpnt, &mapping->i_mmap, pgoff, pgoff) { offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT; addr = mpnt->vm_start + offset; @@ -460,7 +461,7 @@ void flush_dcache_page(struct page *page) } WARN_ON(++count == 4096); } - flush_dcache_mmap_unlock(mapping); + flush_dcache_mmap_unlock_irqrestore(mapping, flags); } EXPORT_SYMBOL(flush_dcache_page);
