On Monday, December 05, 2016 11:19:45 AM cuilifei wrote:
> Freezing process can abort when a client is waiting uninterruptibly
> for a response. Add new macro wait_fatal_freezable to try to fix it.
>
> Signed-off-by: cuilifei <cuili...@xiaomi.com>
I'm not a big fan of this to be honest.
Do we really want to suspend the system (or freeze tasks for other reasons)
if that happens?
> ---
> fs/fuse/dev.c | 30 ++++++++++++++++++++++++++----
> include/linux/freezer.h | 26 ++++++++++++++++++++++++++
> 2 files changed, 52 insertions(+), 4 deletions(-)
>
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index 70ea57c..e33a081 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -19,6 +19,7 @@
> #include <linux/pipe_fs_i.h>
> #include <linux/swap.h>
> #include <linux/splice.h>
> +#include <linux/freezer.h>
>
> MODULE_ALIAS_MISCDEV(FUSE_MINOR);
> MODULE_ALIAS("devname:fuse");
> @@ -99,6 +100,19 @@ void fuse_request_free(struct fuse_req *req)
> kmem_cache_free(fuse_req_cachep, req);
> }
>
> +static void block_sigs(sigset_t *oldset)
> +{
> + sigset_t mask;
> +
> + siginitsetinv(&mask, sigmask(SIGKILL));
> + sigprocmask(SIG_BLOCK, &mask, oldset);
> +}
> +
> +static void restore_sigs(sigset_t *oldset)
> +{
> + sigprocmask(SIG_SETMASK, oldset, NULL);
> +}
> +
> void __fuse_get_request(struct fuse_req *req)
> {
> atomic_inc(&req->count);
> @@ -134,13 +148,18 @@ static struct fuse_req *__fuse_get_req(struct fuse_conn
> *fc, unsigned npages,
> bool for_background)
> {
> struct fuse_req *req;
> + sigset_t oldset;
> + int intr;
> int err;
> atomic_inc(&fc->num_waiting);
>
> if (fuse_block_alloc(fc, for_background)) {
> err = -EINTR;
> - if (wait_event_killable_exclusive(fc->blocked_waitq,
> - !fuse_block_alloc(fc, for_background)))
> + block_sigs(&oldset);
> + intr = wait_fatal_freezable(fc->blocked_waitq,
> + !fuse_block_alloc(fc, for_background), true);
> + restore_sigs(&oldset);
> + if (intr)
> goto out;
> }
> /* Matches smp_wmb() in fuse_set_initialized() */
> @@ -427,9 +446,12 @@ static void request_wait_answer(struct fuse_conn *fc,
> struct fuse_req *req)
> }
>
> if (!test_bit(FR_FORCE, &req->flags)) {
> + sigset_t oldset;
> /* Only fatal signals may interrupt this */
> - err = wait_event_killable(req->waitq,
> - test_bit(FR_FINISHED, &req->flags));
> + block_sigs(&oldset);
> + err = wait_fatal_freezable(req->waitq,
> + test_bit(FR_FINISHED, &req->flags), false);
> + restore_sigs(&oldset);
> if (!err)
> return;
>
> diff --git a/include/linux/freezer.h b/include/linux/freezer.h
> index dd03e83..2504cd0 100644
> --- a/include/linux/freezer.h
> +++ b/include/linux/freezer.h
> @@ -256,6 +256,22 @@ static inline int
> freezable_schedule_hrtimeout_range(ktime_t *expires,
> __retval; \
> })
>
> +#define wait_fatal_freezable(wq, condition, exclusive)
> \
> +({ \
> + int __ret = 0; \
> + do { \
> + if (exclusive) \
> + __ret = wait_event_interruptible_exclusive(wq, \
> + condition); \
> + else \
> + __ret = wait_event_interruptible(wq, \
> + condition); \
> + if (!__ret || fatal_signal_pending(current)) \
> + break; \
> + } while (try_to_freeze()); \
> + __ret; \
> +})
> +
> #else /* !CONFIG_FREEZER */
> static inline bool frozen(struct task_struct *p) { return false; }
> static inline bool freezing(struct task_struct *p) { return false; }
> @@ -296,6 +312,16 @@ static inline void set_freezable(void) {}
> #define wait_event_freezekillable_unsafe(wq, condition)
> \
> wait_event_killable(wq, condition)
>
> +#define wait_fatal_freezable(wq, condition, exclusive)
> \
> +({ \
> + int __ret = 0; \
> + if (exclusive) \
> + __ret = wait_event_killable_exclusive(wq, condition); \
> + else \
> + __ret = wait_event_killable(wq, condition); \
> + __ret; \
> +})
> +
> #endif /* !CONFIG_FREEZER */
>
> #endif /* FREEZER_H_INCLUDED */
>
Thanks,
Rafael
