Messages in this thread Patch in this message | | | Date | Sat, 2 Aug 2003 13:42:27 -0500 | From | Matt Mackall <> | Subject | Re: [PATCH] [1/2] random: SMP locking |
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On Sat, Aug 02, 2003 at 08:35:22AM -0400, Zwane Mwaikambo wrote: > On Sat, 2 Aug 2003, Andrew Morton wrote: > > > Cannot perform userspace access while holding a lock - a pagefault could > > occur, perform IO, schedule away and the same CPU tries to take the same > > lock via a different process. > > Perhaps might_sleep() in *_user, copy_* etc is in order?
I think it's been suggested before, but I threw a patch together for i386 anyway.
This only checks in the non-__ versions, as those are occassionally called inside things like kmap_atomic pairs which take a spinlock in with highmem. It's all conditional on CONFIG_DEBUG_SPINLOCK_SLEEP (which isn't quite the right name) so there's no overhead for normal builds.
diff -urN -X dontdiff orig/arch/i386/lib/usercopy.c work/arch/i386/lib/usercopy.c --- orig/arch/i386/lib/usercopy.c 2003-07-13 22:28:54.000000000 -0500 +++ work/arch/i386/lib/usercopy.c 2003-08-02 13:33:43.000000000 -0500 @@ -149,6 +149,7 @@ unsigned long clear_user(void __user *to, unsigned long n) { + might_sleep(); if (access_ok(VERIFY_WRITE, to, n)) __do_clear_user(to, n); return n; @@ -188,6 +189,8 @@ unsigned long mask = -__addr_ok(s); unsigned long res, tmp; + might_sleep(); + __asm__ __volatile__( " testl %0, %0\n" " jz 3f\n" diff -urN -X dontdiff orig/include/asm-i386/uaccess.h work/include/asm-i386/uaccess.h --- orig/include/asm-i386/uaccess.h 2003-07-13 22:30:48.000000000 -0500 +++ work/include/asm-i386/uaccess.h 2003-08-02 13:15:42.000000000 -0500 @@ -260,6 +260,7 @@ ({ \ long __pu_err = -EFAULT; \ __typeof__(*(ptr)) *__pu_addr = (ptr); \ + might_sleep(); \ if (access_ok(VERIFY_WRITE,__pu_addr,size)) \ __put_user_size((x),__pu_addr,(size),__pu_err,-EFAULT); \ __pu_err; \ @@ -469,6 +470,7 @@ static inline unsigned long copy_to_user(void __user *to, const void *from, unsigned long n) { + might_sleep(); if (access_ok(VERIFY_WRITE, to, n)) n = __copy_to_user(to, from, n); return n; @@ -493,6 +495,7 @@ static inline unsigned long copy_from_user(void *to, const void __user *from, unsigned long n) { + might_sleep(); if (access_ok(VERIFY_READ, from, n)) n = __copy_from_user(to, from, n); else
-- Matt Mackall : http://www.selenic.com : of or relating to the moon - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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