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authorTheodore Ts'o <tytso@mit.edu>2017-06-08 02:01:32 +0300
committerTheodore Ts'o <tytso@mit.edu>2017-06-08 02:01:32 +0300
commit92e75428ffc90e2a0321062379f883f3671cfebe (patch)
treeb06b973a94111993fa11672556d0e0c9d1bd134d /drivers/char/random.c
parent9dfa7bba35ac08a63565d58c454dccb7e1bb0a08 (diff)
downloadlinux-92e75428ffc90e2a0321062379f883f3671cfebe.tar.xz
random: use lockless method of accessing and updating f->reg_idx
Linus pointed out that there is a much more efficient way of avoiding the problem that we were trying to address in commit 9dfa7bba35ac0: "fix race in drivers/char/random.c:get_reg()". Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'drivers/char/random.c')
-rw-r--r--drivers/char/random.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index a561f0c2f428..473ad34378f2 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1097,15 +1097,15 @@ static void add_interrupt_bench(cycles_t start)
static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
{
__u32 *ptr = (__u32 *) regs;
- unsigned long flags;
+ unsigned int idx;
if (regs == NULL)
return 0;
- local_irq_save(flags);
- if (f->reg_idx >= sizeof(struct pt_regs) / sizeof(__u32))
- f->reg_idx = 0;
- ptr += f->reg_idx++;
- local_irq_restore(flags);
+ idx = READ_ONCE(f->reg_idx);
+ if (idx >= sizeof(struct pt_regs) / sizeof(__u32))
+ idx = 0;
+ ptr += idx++;
+ WRITE_ONCE(f->reg_idx, idx);
return *ptr;
}