forked from Minki/linux
14d0ee0517
The first two fix the case where full RCU debugging is enabled, enabling function tracing causes a live lock of the system. This is due to the added debug checks in rcu_dereference_raw() that is used by the function tracer. These checks are also traced by the function tracer as well as cause enough overhead to the function tracer to slow down the system enough that the time to finish an interrupt can take longer than when the next interrupt is triggered, causing a live lock from the timer interrupt. Talking this over with Paul McKenney, we came up with a fix that adds a new rcu_dereference_raw_notrace() that does not perform these added checks, and let the function tracer use that. The third commit fixes a failed compile when branch tracing is enabled, due to the conversion of the trace_test_buffer() selftest that the branch trace wasn't converted for. The forth patch fixes a bug caught by the RCU lockdep code where a rcu_read_lock() is performed when rcu is disabled (either going to or from idle, or user space). This happened on the irqsoff tracer as it calls task_uid(). The fix here was to use current_uid() when possible that doesn't use rcu locking. Which luckily, is always used when irqsoff calls this code. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQEcBAABAgAGBQJRsQZhAAoJEOdOSU1xswtMquIH/0zyrqrLTnkc5MsNnnJ8kH5R z1cULts4FqBTUNZ1hdb3BTOu4zywjREIkWfM9qqpBmq9Mq6PBxX7gxWTqYvD4jiX EatiiCKa7Fyddx4iHJNfvtWgKVYt9WKSNeloRugS9h7NxIZ1wpz21DUpENFQzW2f jWRnq/AKXFmZ0vn1953mPePtRsg61RYpb7DCkTE1gtUnvL43wMd/Mo6p6BLMEG26 1dDK6EWO/uewl8A4oP5JZYP+AP5Ckd4x1PuQK682AtQw+8S6etaGfeJr0WZmKQoD 0aDZ/NXXSNKChlUFGJusBNJCWryONToa+sdiKuk1h/lW/k9Mail/FChiHBzMiwk= =uvlD -----END PGP SIGNATURE----- Merge tag 'trace-fixes-v3.10-rc3-v3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace Pull tracing fixes from Steven Rostedt: "This contains 4 fixes. The first two fix the case where full RCU debugging is enabled, enabling function tracing causes a live lock of the system. This is due to the added debug checks in rcu_dereference_raw() that is used by the function tracer. These checks are also traced by the function tracer as well as cause enough overhead to the function tracer to slow down the system enough that the time to finish an interrupt can take longer than when the next interrupt is triggered, causing a live lock from the timer interrupt. Talking this over with Paul McKenney, we came up with a fix that adds a new rcu_dereference_raw_notrace() that does not perform these added checks, and let the function tracer use that. The third commit fixes a failed compile when branch tracing is enabled, due to the conversion of the trace_test_buffer() selftest that the branch trace wasn't converted for. The forth patch fixes a bug caught by the RCU lockdep code where a rcu_read_lock() is performed when rcu is disabled (either going to or from idle, or user space). This happened on the irqsoff tracer as it calls task_uid(). The fix here was to use current_uid() when possible that doesn't use rcu locking. Which luckily, is always used when irqsoff calls this code." * tag 'trace-fixes-v3.10-rc3-v3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing: Use current_uid() for critical time tracing tracing: Fix bad parameter passed in branch selftest ftrace: Use the rcu _notrace variants for rcu_dereference_raw() and friends rcu: Add _notrace variation of rcu_dereference_raw() and hlist_for_each_entry_rcu() |
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