diff options
| author | Theodore Ts'o <tytso@mit.edu> | 2017-06-07 19:01:32 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2017-06-07 19:01:32 -0400 |
| commit | 92e75428ffc90e2a0321062379f883f3671cfebe (patch) | |
| tree | b06b973a94111993fa11672556d0e0c9d1bd134d /drivers | |
| parent | 9dfa7bba35ac08a63565d58c454dccb7e1bb0a08 (diff) | |
| download | linux-stable-92e75428ffc90e2a0321062379f883f3671cfebe.tar.gz linux-stable-92e75428ffc90e2a0321062379f883f3671cfebe.tar.bz2 linux-stable-92e75428ffc90e2a0321062379f883f3671cfebe.zip | |
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')
| -rw-r--r-- | drivers/char/random.c | 12 |
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; } |