The function flush_signals clears all pending signals for the process. It may be used by kernel threads when we need to prepare a kernel thread for responding to signals. However using this function for an userspaces processes is incorrect - clearing signals without the program expecting it can cause misbehavior.
The raid1 and raid5 code uses flush_signals in its request routine because it wants to prepare for an interruptible wait. This patch drops flush_signals and uses sigprocmask instead to block all signals (including SIGKILL) around the schedule() call. The signals are not lost, but the schedule() call won't respond to them. Signed-off-by: Mikulas Patocka <[email protected]> Cc: [email protected] --- drivers/md/raid1.c | 5 ++++- drivers/md/raid5.c | 5 ++++- 2 files changed, 8 insertions(+), 2 deletions(-) Index: linux-4.12-rc4/drivers/md/raid1.c =================================================================== --- linux-4.12-rc4.orig/drivers/md/raid1.c +++ linux-4.12-rc4/drivers/md/raid1.c @@ -1335,7 +1335,7 @@ static void raid1_write_request(struct m */ DEFINE_WAIT(w); for (;;) { - flush_signals(current); + sigset_t full, old; prepare_to_wait(&conf->wait_barrier, &w, TASK_INTERRUPTIBLE); if (bio_end_sector(bio) <= mddev->suspend_lo || @@ -1345,7 +1345,10 @@ static void raid1_write_request(struct m bio->bi_iter.bi_sector, bio_end_sector(bio)))) break; + sigfillset(&full); + sigprocmask(SIG_BLOCK, &full, &old); schedule(); + sigprocmask(SIG_SETMASK, &old, NULL); } finish_wait(&conf->wait_barrier, &w); } Index: linux-4.12-rc4/drivers/md/raid5.c =================================================================== --- linux-4.12-rc4.orig/drivers/md/raid5.c +++ linux-4.12-rc4/drivers/md/raid5.c @@ -5693,12 +5693,15 @@ static void raid5_make_request(struct md * userspace, we want an interruptible * wait. */ - flush_signals(current); prepare_to_wait(&conf->wait_for_overlap, &w, TASK_INTERRUPTIBLE); if (logical_sector >= mddev->suspend_lo && logical_sector < mddev->suspend_hi) { + sigset_t full, old; + sigfillset(&full); + sigprocmask(SIG_BLOCK, &full, &old); schedule(); + sigprocmask(SIG_SETMASK, &old, NULL); do_prepare = true; } goto retry;
