From: David Howells <[email protected]>
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 <[email protected]>
---
mm/nommu.c | 14 +++++++++-----
1 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/mm/nommu.c b/mm/nommu.c
index a0ba6ac..3215f46 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -327,6 +327,15 @@ struct vm_area_struct *find_vma(struct m
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
*/
@@ -1130,11 +1139,6 @@ struct page *follow_page(struct vm_area_
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)
{
-
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