From 831441862956fffa17b9801db37e6ea1650b0f69 Mon Sep 17 00:00:00 2001 From: Rafael J. Wysocki Date: Tue, 17 Jul 2007 04:03:35 -0700 Subject: Freezer: make kernel threads nonfreezable by default Currently, the freezer treats all tasks as freezable, except for the kernel threads that explicitly set the PF_NOFREEZE flag for themselves. This approach is problematic, since it requires every kernel thread to either set PF_NOFREEZE explicitly, or call try_to_freeze(), even if it doesn't care for the freezing of tasks at all. It seems better to only require the kernel threads that want to or need to be frozen to use some freezer-related code and to remove any freezer-related code from the other (nonfreezable) kernel threads, which is done in this patch. The patch causes all kernel threads to be nonfreezable by default (ie. to have PF_NOFREEZE set by default) and introduces the set_freezable() function that should be called by the freezable kernel threads in order to unset PF_NOFREEZE. It also makes all of the currently freezable kernel threads call set_freezable(), so it shouldn't cause any (intentional) change of behaviour to appear. Additionally, it updates documentation to describe the freezing of tasks more accurately. [akpm@linux-foundation.org: build fixes] Signed-off-by: Rafael J. Wysocki Acked-by: Nigel Cunningham Cc: Pavel Machek Cc: Oleg Nesterov Cc: Gautham R Shenoy Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/usb/atm/ueagle-atm.c | 1 + drivers/usb/core/hub.c | 1 + drivers/usb/gadget/file_storage.c | 3 +++ drivers/usb/storage/usb.c | 3 +-- 4 files changed, 6 insertions(+), 2 deletions(-) (limited to 'drivers/usb') diff --git a/drivers/usb/atm/ueagle-atm.c b/drivers/usb/atm/ueagle-atm.c index 4973e147bc79..8f046659b4e9 100644 --- a/drivers/usb/atm/ueagle-atm.c +++ b/drivers/usb/atm/ueagle-atm.c @@ -1168,6 +1168,7 @@ static int uea_kthread(void *data) struct uea_softc *sc = data; int ret = -EAGAIN; + set_freezable(); uea_enters(INS_TO_USBDEV(sc)); while (!kthread_should_stop()) { if (ret < 0 || sc->reset) diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 50e79010401c..fd74c50b1804 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -2728,6 +2728,7 @@ loop: static int hub_thread(void *__unused) { + set_freezable(); do { hub_events(); wait_event_interruptible(khubd_wait, diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c index 8712ef987179..be7a1bd2823b 100644 --- a/drivers/usb/gadget/file_storage.c +++ b/drivers/usb/gadget/file_storage.c @@ -3434,6 +3434,9 @@ static int fsg_main_thread(void *fsg_) allow_signal(SIGKILL); allow_signal(SIGUSR1); + /* Allow the thread to be frozen */ + set_freezable(); + /* Arrange for userspace references to be interpreted as kernel * pointers. That way we can pass a kernel pointer to a routine * that expects a __user pointer and it will work okay. */ diff --git a/drivers/usb/storage/usb.c b/drivers/usb/storage/usb.c index bef8bcd9bd98..28842d208bb0 100644 --- a/drivers/usb/storage/usb.c +++ b/drivers/usb/storage/usb.c @@ -311,8 +311,6 @@ static int usb_stor_control_thread(void * __us) struct Scsi_Host *host = us_to_host(us); int autopm_rc; - current->flags |= PF_NOFREEZE; - for(;;) { US_DEBUGP("*** thread sleeping.\n"); if(down_interruptible(&us->sema)) @@ -920,6 +918,7 @@ static int usb_stor_scan_thread(void * __us) printk(KERN_DEBUG "usb-storage: device found at %d\n", us->pusb_dev->devnum); + set_freezable(); /* Wait for the timeout to expire or for a disconnect */ if (delay_use > 0) { printk(KERN_DEBUG "usb-storage: waiting for device " -- cgit v1.2.3