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fbdev: add mutex for fb_mmap locking

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Add a mutex to avoid a circular locking problem between the mm layer
semaphore and fbdev ioctl mutex through the fb_mmap() call.

Also, add mutex to all places where smem_start and smem_len fields change
so the mutex inside the fb_mmap() is actually used.  Changing of these
fields before calling the framebuffer_register() are not mutexed.

This is 2.6.31 material.  It removes one lockdep (fb_mmap() and
register_framebuffer()) but there is still another one (fb_release() and
register_framebuffer()).  It also cleans up handling of the smem_start and
smem_len fields used by mutexed section of the fb_mmap().

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Krzysztof Helt
2009-06-30 11:41:29 -07:00
committed by Linus Torvalds
parent 70d6027ff2
commit 537a1bf059
16 changed files with 74 additions and 42 deletions
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2
drivers/video/w100fb.c
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@@ -523,6 +523,7 @@ static int w100fb_set_par(struct fb_info *info)
info->fix.ywrapstep = 0;
info->fix.line_length = par->xres * BITS_PER_PIXEL / 8;
mutex_lock(&info->mm_lock);
if ((par->xres*par->yres*BITS_PER_PIXEL/8) > (MEM_INT_SIZE+1)) {
par->extmem_active = 1;
info->fix.smem_len = par->mach->mem->size+1;
@@ -530,6 +531,7 @@ static int w100fb_set_par(struct fb_info *info)
par->extmem_active = 0;
info->fix.smem_len = MEM_INT_SIZE+1;
}
mutex_unlock(&info->mm_lock);
w100fb_activate_var(par);
}