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authorAlan Stern <stern@rowland.harvard.edu>2006-03-27 04:16:30 -0500
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-27 11:44:50 -0500
commite041c683412d5bf44dc2b109053e3b837b71742d (patch)
tree9d271066ef379da0c0fb3b8cb4137abd5d2ebba0 /drivers/video/fbmem.c
parent76b81e2b0e2241accebcc68e126bc5ab958661b9 (diff)
[PATCH] Notifier chain update: API changes
The kernel's implementation of notifier chains is unsafe. There is no protection against entries being added to or removed from a chain while the chain is in use. The issues were discussed in this thread: http://marc.theaimsgroup.com/?l=linux-kernel&m=113018709002036&w=2 We noticed that notifier chains in the kernel fall into two basic usage classes: "Blocking" chains are always called from a process context and the callout routines are allowed to sleep; "Atomic" chains can be called from an atomic context and the callout routines are not allowed to sleep. We decided to codify this distinction and make it part of the API. Therefore this set of patches introduces three new, parallel APIs: one for blocking notifiers, one for atomic notifiers, and one for "raw" notifiers (which is really just the old API under a new name). New kinds of data structures are used for the heads of the chains, and new routines are defined for registration, unregistration, and calling a chain. The three APIs are explained in include/linux/notifier.h and their implementation is in kernel/sys.c. With atomic and blocking chains, the implementation guarantees that the chain links will not be corrupted and that chain callers will not get messed up by entries being added or removed. For raw chains the implementation provides no guarantees at all; users of this API must provide their own protections. (The idea was that situations may come up where the assumptions of the atomic and blocking APIs are not appropriate, so it should be possible for users to handle these things in their own way.) There are some limitations, which should not be too hard to live with. For atomic/blocking chains, registration and unregistration must always be done in a process context since the chain is protected by a mutex/rwsem. Also, a callout routine for a non-raw chain must not try to register or unregister entries on its own chain. (This did happen in a couple of places and the code had to be changed to avoid it.) Since atomic chains may be called from within an NMI handler, they cannot use spinlocks for synchronization. Instead we use RCU. The overhead falls almost entirely in the unregister routine, which is okay since unregistration is much less frequent that calling a chain. Here is the list of chains that we adjusted and their classifications. None of them use the raw API, so for the moment it is only a placeholder. ATOMIC CHAINS ------------- arch/i386/kernel/traps.c: i386die_chain arch/ia64/kernel/traps.c: ia64die_chain arch/powerpc/kernel/traps.c: powerpc_die_chain arch/sparc64/kernel/traps.c: sparc64die_chain arch/x86_64/kernel/traps.c: die_chain drivers/char/ipmi/ipmi_si_intf.c: xaction_notifier_list kernel/panic.c: panic_notifier_list kernel/profile.c: task_free_notifier net/bluetooth/hci_core.c: hci_notifier net/ipv4/netfilter/ip_conntrack_core.c: ip_conntrack_chain net/ipv4/netfilter/ip_conntrack_core.c: ip_conntrack_expect_chain net/ipv6/addrconf.c: inet6addr_chain net/netfilter/nf_conntrack_core.c: nf_conntrack_chain net/netfilter/nf_conntrack_core.c: nf_conntrack_expect_chain net/netlink/af_netlink.c: netlink_chain BLOCKING CHAINS --------------- arch/powerpc/platforms/pseries/reconfig.c: pSeries_reconfig_chain arch/s390/kernel/process.c: idle_chain arch/x86_64/kernel/process.c idle_notifier drivers/base/memory.c: memory_chain drivers/cpufreq/cpufreq.c cpufreq_policy_notifier_list drivers/cpufreq/cpufreq.c cpufreq_transition_notifier_list drivers/macintosh/adb.c: adb_client_list drivers/macintosh/via-pmu.c sleep_notifier_list drivers/macintosh/via-pmu68k.c sleep_notifier_list drivers/macintosh/windfarm_core.c wf_client_list drivers/usb/core/notify.c usb_notifier_list drivers/video/fbmem.c fb_notifier_list kernel/cpu.c cpu_chain kernel/module.c module_notify_list kernel/profile.c munmap_notifier kernel/profile.c task_exit_notifier kernel/sys.c reboot_notifier_list net/core/dev.c netdev_chain net/decnet/dn_dev.c: dnaddr_chain net/ipv4/devinet.c: inetaddr_chain It's possible that some of these classifications are wrong. If they are, please let us know or submit a patch to fix them. Note that any chain that gets called very frequently should be atomic, because the rwsem read-locking used for blocking chains is very likely to incur cache misses on SMP systems. (However, if the chain's callout routines may sleep then the chain cannot be atomic.) The patch set was written by Alan Stern and Chandra Seetharaman, incorporating material written by Keith Owens and suggestions from Paul McKenney and Andrew Morton. [jes@sgi.com: restructure the notifier chain initialization macros] Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com> Signed-off-by: Jes Sorensen <jes@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers/video/fbmem.c')
-rw-r--r--drivers/video/fbmem.c31
1 files changed, 17 insertions, 14 deletions
diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index 07d882b14396..b1a8dca76430 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -55,7 +55,7 @@
55 55
56#define FBPIXMAPSIZE (1024 * 8) 56#define FBPIXMAPSIZE (1024 * 8)
57 57
58static struct notifier_block *fb_notifier_list; 58static BLOCKING_NOTIFIER_HEAD(fb_notifier_list);
59struct fb_info *registered_fb[FB_MAX]; 59struct fb_info *registered_fb[FB_MAX];
60int num_registered_fb; 60int num_registered_fb;
61 61
@@ -784,7 +784,7 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
784 784
785 event.info = info; 785 event.info = info;
786 event.data = &mode1; 786 event.data = &mode1;
787 ret = notifier_call_chain(&fb_notifier_list, 787 ret = blocking_notifier_call_chain(&fb_notifier_list,
788 FB_EVENT_MODE_DELETE, &event); 788 FB_EVENT_MODE_DELETE, &event);
789 } 789 }
790 790
@@ -830,8 +830,8 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
830 830
831 info->flags &= ~FBINFO_MISC_USEREVENT; 831 info->flags &= ~FBINFO_MISC_USEREVENT;
832 event.info = info; 832 event.info = info;
833 notifier_call_chain(&fb_notifier_list, evnt, 833 blocking_notifier_call_chain(&fb_notifier_list,
834 &event); 834 evnt, &event);
835 } 835 }
836 } 836 }
837 } 837 }
@@ -854,7 +854,8 @@ fb_blank(struct fb_info *info, int blank)
854 854
855 event.info = info; 855 event.info = info;
856 event.data = &blank; 856 event.data = &blank;
857 notifier_call_chain(&fb_notifier_list, FB_EVENT_BLANK, &event); 857 blocking_notifier_call_chain(&fb_notifier_list,
858 FB_EVENT_BLANK, &event);
858 } 859 }
859 860
860 return ret; 861 return ret;
@@ -925,7 +926,7 @@ fb_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
925 con2fb.framebuffer = -1; 926 con2fb.framebuffer = -1;
926 event.info = info; 927 event.info = info;
927 event.data = &con2fb; 928 event.data = &con2fb;
928 notifier_call_chain(&fb_notifier_list, 929 blocking_notifier_call_chain(&fb_notifier_list,
929 FB_EVENT_GET_CONSOLE_MAP, &event); 930 FB_EVENT_GET_CONSOLE_MAP, &event);
930 return copy_to_user(argp, &con2fb, 931 return copy_to_user(argp, &con2fb,
931 sizeof(con2fb)) ? -EFAULT : 0; 932 sizeof(con2fb)) ? -EFAULT : 0;
@@ -944,7 +945,7 @@ fb_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
944 return -EINVAL; 945 return -EINVAL;
945 event.info = info; 946 event.info = info;
946 event.data = &con2fb; 947 event.data = &con2fb;
947 return notifier_call_chain(&fb_notifier_list, 948 return blocking_notifier_call_chain(&fb_notifier_list,
948 FB_EVENT_SET_CONSOLE_MAP, 949 FB_EVENT_SET_CONSOLE_MAP,
949 &event); 950 &event);
950 case FBIOBLANK: 951 case FBIOBLANK:
@@ -1324,7 +1325,7 @@ register_framebuffer(struct fb_info *fb_info)
1324 devfs_mk_cdev(MKDEV(FB_MAJOR, i), 1325 devfs_mk_cdev(MKDEV(FB_MAJOR, i),
1325 S_IFCHR | S_IRUGO | S_IWUGO, "fb/%d", i); 1326 S_IFCHR | S_IRUGO | S_IWUGO, "fb/%d", i);
1326 event.info = fb_info; 1327 event.info = fb_info;
1327 notifier_call_chain(&fb_notifier_list, 1328 blocking_notifier_call_chain(&fb_notifier_list,
1328 FB_EVENT_FB_REGISTERED, &event); 1329 FB_EVENT_FB_REGISTERED, &event);
1329 return 0; 1330 return 0;
1330} 1331}
@@ -1366,7 +1367,7 @@ unregister_framebuffer(struct fb_info *fb_info)
1366 */ 1367 */
1367int fb_register_client(struct notifier_block *nb) 1368int fb_register_client(struct notifier_block *nb)
1368{ 1369{
1369 return notifier_chain_register(&fb_notifier_list, nb); 1370 return blocking_notifier_chain_register(&fb_notifier_list, nb);
1370} 1371}
1371 1372
1372/** 1373/**
@@ -1375,7 +1376,7 @@ int fb_register_client(struct notifier_block *nb)
1375 */ 1376 */
1376int fb_unregister_client(struct notifier_block *nb) 1377int fb_unregister_client(struct notifier_block *nb)
1377{ 1378{
1378 return notifier_chain_unregister(&fb_notifier_list, nb); 1379 return blocking_notifier_chain_unregister(&fb_notifier_list, nb);
1379} 1380}
1380 1381
1381/** 1382/**
@@ -1393,11 +1394,13 @@ void fb_set_suspend(struct fb_info *info, int state)
1393 1394
1394 event.info = info; 1395 event.info = info;
1395 if (state) { 1396 if (state) {
1396 notifier_call_chain(&fb_notifier_list, FB_EVENT_SUSPEND, &event); 1397 blocking_notifier_call_chain(&fb_notifier_list,
1398 FB_EVENT_SUSPEND, &event);
1397 info->state = FBINFO_STATE_SUSPENDED; 1399 info->state = FBINFO_STATE_SUSPENDED;
1398 } else { 1400 } else {
1399 info->state = FBINFO_STATE_RUNNING; 1401 info->state = FBINFO_STATE_RUNNING;
1400 notifier_call_chain(&fb_notifier_list, FB_EVENT_RESUME, &event); 1402 blocking_notifier_call_chain(&fb_notifier_list,
1403 FB_EVENT_RESUME, &event);
1401 } 1404 }
1402} 1405}
1403 1406
@@ -1469,7 +1472,7 @@ int fb_new_modelist(struct fb_info *info)
1469 1472
1470 if (!list_empty(&info->modelist)) { 1473 if (!list_empty(&info->modelist)) {
1471 event.info = info; 1474 event.info = info;
1472 err = notifier_call_chain(&fb_notifier_list, 1475 err = blocking_notifier_call_chain(&fb_notifier_list,
1473 FB_EVENT_NEW_MODELIST, 1476 FB_EVENT_NEW_MODELIST,
1474 &event); 1477 &event);
1475 } 1478 }
@@ -1495,7 +1498,7 @@ int fb_con_duit(struct fb_info *info, int event, void *data)
1495 evnt.info = info; 1498 evnt.info = info;
1496 evnt.data = data; 1499 evnt.data = data;
1497 1500
1498 return notifier_call_chain(&fb_notifier_list, event, &evnt); 1501 return blocking_notifier_call_chain(&fb_notifier_list, event, &evnt);
1499} 1502}
1500EXPORT_SYMBOL(fb_con_duit); 1503EXPORT_SYMBOL(fb_con_duit);
1501 1504