From 930e652a21a08986b03d1f370f933057dc0db2dc Mon Sep 17 00:00:00 2001 From: David Howells Date: Wed, 27 Sep 2006 01:50:22 -0700 Subject: [PATCH] [PATCH] NOMMU: Make futexes work under NOMMU conditions Make futexes work under NOMMU conditions. This can be tested by running this in one shell: #define SYSERROR(X, Y) \ do { if ((long)(X) == -1L) { perror(Y); exit(1); }} while(0) int main() { int shmid, tmp, *f, n; shmid = shmget(23, 4, IPC_CREAT|0666); SYSERROR(shmid, "shmget"); f = shmat(shmid, NULL, 0); SYSERROR(f, "shmat"); n = *f; printf("WAIT: %p{%x}\n", f, n); tmp = futex(f, FUTEX_WAIT, n, NULL, NULL, 0); SYSERROR(tmp, "futex"); printf("WAITED: %d\n", tmp); tmp = shmdt(f); SYSERROR(tmp, "shmdt"); exit(0); } And then this in the other shell: #define SYSERROR(X, Y) \ do { if ((long)(X) == -1L) { perror(Y); exit(1); }} while(0) int main() { int shmid, tmp, *f; shmid = shmget(23, 4, IPC_CREAT|0666); SYSERROR(shmid, "shmget"); f = shmat(shmid, NULL, 0); SYSERROR(f, "shmat"); (*f)++; printf("WAKE: %p{%x}\n", f, *f); tmp = futex(f, FUTEX_WAKE, 1, NULL, NULL, 0); SYSERROR(tmp, "futex"); printf("WOKE: %d\n", tmp); tmp = shmdt(f); SYSERROR(tmp, "shmdt"); exit(0); } The first program will set up a SYSV IPC SHM segment and wait on a futex in it for the number at the start to change. The program will increment that number and wake the first program up. This leads to output of the form: SHELL 1 SHELL 2 ======================= ======================= # /dowait WAIT: 0xc32ac000{0} # /dowake WAKE: 0xc32ac000{1} WAITED: 0 WOKE: 1 Signed-off-by: David Howells Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/nommu-mmap.txt | 10 ++++++++++ mm/nommu.c | 14 +++++++++----- 2 files changed, 19 insertions(+), 5 deletions(-) diff --git a/Documentation/nommu-mmap.txt b/Documentation/nommu-mmap.txt index 4db7c18bf68c..7714f57caad5 100644 --- a/Documentation/nommu-mmap.txt +++ b/Documentation/nommu-mmap.txt @@ -138,6 +138,16 @@ mode. The former through the usual mechanism, the latter through files created on ramfs or tmpfs mounts. +======= +FUTEXES +======= + +Futexes are supported in NOMMU mode if the arch supports them. An error will +be given if an address passed to the futex system call lies outside the +mappings made by a process or if the mapping in which the address lies does not +support futexes (such as an I/O chardev mapping). + + ============= NO-MMU MREMAP ============= diff --git a/mm/nommu.c b/mm/nommu.c index 23cfa8ec914a..564540662192 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -349,6 +349,15 @@ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) } EXPORT_SYMBOL(find_vma); +/* + * find a VMA + * - we don't extend stack VMAs under NOMMU conditions + */ +struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr) +{ + return find_vma(mm, addr); +} + /* * look up the first VMA exactly that exactly matches addr * - should be called with mm->mmap_sem at least held readlocked @@ -1153,11 +1162,6 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, return NULL; } -struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr) -{ - return NULL; -} - int remap_pfn_range(struct vm_area_struct *vma, unsigned long from, unsigned long to, unsigned long size, pgprot_t prot) { -- 2.30.2