signal: Don't send siginfo to kthreads.

Today kernel threads never dequeue siginfo so it is pointless to enqueue siginfo for them. The usb gadget mass storage driver goes one farther and uses SEND_SIG_FORCED to guarantee that no siginfo is even enqueued. Generalize the optimization of the usb mass storage driver and never perform an unnecessary allocation when delivering signals to kthreads. Switch the mass storage driver from sending signals with SEND_SIG_FORCED to SEND_SIG_PRIV. As using SEND_SIG_FORCED is now unnecessary. Reviewed-by: Thomas Gleixner <[email protected]> Signed-off-by: "Eric W. Biederman" <[email protected]>
kawasaki · Sep 11, 2018 · 0351505 · 0351505
1 parent 961366a
commit 0351505
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diff --git a/drivers/usb/gadget/function/f_mass_storage.c b/drivers/usb/gadget/function/f_mass_storage.c
@@ -403,7 +403,7 @@ static void raise_exception(struct fsg_common *common, enum fsg_state new_state)
 		common->exception_req_tag = common->ep0_req_tag;
 		common->state = new_state;
 		if (common->thread_task)
-			send_sig_info(SIGUSR1, SEND_SIG_FORCED,
+			send_sig_info(SIGUSR1, SEND_SIG_PRIV,
 				      common->thread_task);
 	}
 	spin_unlock_irqrestore(&common->lock, flags);

diff --git a/kernel/signal.c b/kernel/signal.c
@@ -1057,7 +1057,7 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
 	 * fast-pathed signals for kernel-internal things like SIGSTOP
 	 * or SIGKILL.
 	 */
-	if (info == SEND_SIG_FORCED)
+	if ((info == SEND_SIG_FORCED) || (t->flags & PF_KTHREAD))
 		goto out_set;
 
 	/*