Fix fasttrap tracepoint locking.
Upstream, tracepoints are protected by per-CPU mutexes. An unlinked tracepoint may be freed once all the tracepoint mutexes have been acquired and released - this is done in fasttrap_mod_barrier(). This mechanism was not properly ported: in some places, the proc lock is used in place of a tracepoint lock, and in others the locking is omitted entirely. This change implements tracepoint locking with an rmlock, where the read lock is used in fasttrap probe context. As a side effect, this fixes a recursion on the proc lock when the raise action is used from a userland probe. MFC after: 1 month
This commit is contained in:
Mark Johnston
parent
90e7434a6d
commit
380344a7af
@ -63,13 +63,16 @@
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#ifndef illumos
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#include <sys/dtrace_bsd.h>
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#include <sys/eventhandler.h>
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#include <sys/rmlock.h>
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#include <sys/sysctl.h>
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#include <sys/u8_textprep.h>
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#include <sys/user.h>
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#include <vm/vm.h>
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#include <vm/pmap.h>
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#include <vm/vm_map.h>
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#include <vm/vm_param.h>
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#include <cddl/dev/dtrace/dtrace_cddl.h>
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#endif
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@ -224,7 +227,7 @@ static void fasttrap_thread_dtor(void *, struct thread *);
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#define FASTTRAP_PROCS_INDEX(pid) ((pid) & fasttrap_procs.fth_mask)
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#ifndef illumos
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static kmutex_t fasttrap_cpuc_pid_lock[MAXCPU];
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struct rmlock fasttrap_tp_lock;
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static eventhandler_tag fasttrap_thread_dtor_tag;
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#endif
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@ -439,10 +442,15 @@ fasttrap_mod_barrier(uint64_t gen)
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fasttrap_mod_gen++;
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#ifdef illumos
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CPU_FOREACH(i) {
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mutex_enter(&fasttrap_cpuc_pid_lock[i]);
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mutex_exit(&fasttrap_cpuc_pid_lock[i]);
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}
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#else
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rm_wlock(&fasttrap_tp_lock);
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rm_wunlock(&fasttrap_tp_lock);
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#endif
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}
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/*
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@ -2574,10 +2582,7 @@ fasttrap_load(void)
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mutex_init(&fasttrap_procs.fth_table[i].ftb_mtx,
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"processes bucket mtx", MUTEX_DEFAULT, NULL);
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CPU_FOREACH(i) {
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mutex_init(&fasttrap_cpuc_pid_lock[i], "fasttrap barrier",
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MUTEX_DEFAULT, NULL);
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}
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rm_init(&fasttrap_tp_lock, "fasttrap tracepoint");
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/*
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* This event handler must run before kdtrace_thread_dtor() since it
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@ -2710,9 +2715,7 @@ fasttrap_unload(void)
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#ifndef illumos
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destroy_dev(fasttrap_cdev);
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mutex_destroy(&fasttrap_count_mtx);
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CPU_FOREACH(i) {
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mutex_destroy(&fasttrap_cpuc_pid_lock[i]);
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}
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rm_destroy(&fasttrap_tp_lock);
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#endif
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return (0);
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@ -206,6 +206,10 @@ extern fasttrap_scrspace_t *fasttrap_scraddr(struct thread *,
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extern dtrace_id_t fasttrap_probe_id;
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extern fasttrap_hash_t fasttrap_tpoints;
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#ifndef illumos
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extern struct rmlock fasttrap_tp_lock;
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#endif
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#define FASTTRAP_TPOINTS_INDEX(pid, pc) \
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(((pc) / sizeof (fasttrap_instr_t) + (pid)) & fasttrap_tpoints.fth_mask)
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@ -46,6 +46,7 @@
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#include <cddl/dev/dtrace/dtrace_cddl.h>
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#include <sys/types.h>
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#include <sys/proc.h>
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#include <sys/rmlock.h>
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#include <sys/dtrace_bsd.h>
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#include <cddl/dev/dtrace/x86/regset.h>
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#include <machine/segments.h>
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@ -737,11 +738,13 @@ fasttrap_return_common(struct reg *rp, uintptr_t pc, pid_t pid,
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fasttrap_id_t *id;
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#ifdef illumos
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kmutex_t *pid_mtx;
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#endif
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#ifdef illumos
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pid_mtx = &cpu_core[CPU->cpu_id].cpuc_pid_lock;
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mutex_enter(pid_mtx);
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#else
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struct rm_priotracker tracker;
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rm_rlock(&fasttrap_tp_lock, &tracker);
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#endif
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bucket = &fasttrap_tpoints.fth_table[FASTTRAP_TPOINTS_INDEX(pid, pc)];
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@ -759,6 +762,8 @@ fasttrap_return_common(struct reg *rp, uintptr_t pc, pid_t pid,
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if (tp == NULL) {
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#ifdef illumos
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mutex_exit(pid_mtx);
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#else
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rm_runlock(&fasttrap_tp_lock, &tracker);
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#endif
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return;
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}
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@ -782,6 +787,8 @@ fasttrap_return_common(struct reg *rp, uintptr_t pc, pid_t pid,
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#ifdef illumos
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mutex_exit(pid_mtx);
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#else
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rm_runlock(&fasttrap_tp_lock, &tracker);
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#endif
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}
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@ -990,6 +997,7 @@ fasttrap_pid_probe(struct reg *rp)
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{
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proc_t *p = curproc;
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#ifndef illumos
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struct rm_priotracker tracker;
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proc_t *pp;
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#endif
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uintptr_t pc = rp->r_rip - 1;
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@ -1049,8 +1057,7 @@ fasttrap_pid_probe(struct reg *rp)
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sx_sunlock(&proctree_lock);
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pp = NULL;
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PROC_LOCK(p);
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_PHOLD(p);
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rm_rlock(&fasttrap_tp_lock, &tracker);
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#endif
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bucket = &fasttrap_tpoints.fth_table[FASTTRAP_TPOINTS_INDEX(pid, pc)];
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@ -1073,8 +1080,7 @@ fasttrap_pid_probe(struct reg *rp)
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#ifdef illumos
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mutex_exit(pid_mtx);
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#else
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_PRELE(p);
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PROC_UNLOCK(p);
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rm_runlock(&fasttrap_tp_lock, &tracker);
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#endif
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return (-1);
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}
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@ -1200,7 +1206,7 @@ fasttrap_pid_probe(struct reg *rp)
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#ifdef illumos
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mutex_exit(pid_mtx);
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#else
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PROC_UNLOCK(p);
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rm_runlock(&fasttrap_tp_lock, &tracker);
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#endif
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tp = &tp_local;
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@ -1813,7 +1819,6 @@ done:
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#ifndef illumos
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PROC_LOCK(p);
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proc_write_regs(curthread, rp);
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_PRELE(p);
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PROC_UNLOCK(p);
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#endif
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@ -33,6 +33,7 @@
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#include <sys/types.h>
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#include <sys/uio.h>
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#include <sys/ptrace.h>
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#include <sys/rmlock.h>
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#include <sys/sysent.h>
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#define OP(x) ((x) >> 26)
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@ -288,10 +289,12 @@ static void
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fasttrap_return_common(struct reg *rp, uintptr_t pc, pid_t pid,
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uintptr_t new_pc)
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{
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struct rm_priotracker tracker;
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fasttrap_tracepoint_t *tp;
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fasttrap_bucket_t *bucket;
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fasttrap_id_t *id;
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rm_rlock(&fasttrap_tp_lock, &tracker);
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bucket = &fasttrap_tpoints.fth_table[FASTTRAP_TPOINTS_INDEX(pid, pc)];
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for (tp = bucket->ftb_data; tp != NULL; tp = tp->ftt_next) {
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@ -306,6 +309,7 @@ fasttrap_return_common(struct reg *rp, uintptr_t pc, pid_t pid,
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* is not essential to the correct execution of the process.
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*/
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if (tp == NULL) {
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rm_runlock(&fasttrap_tp_lock, &tracker);
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return;
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}
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@ -323,6 +327,7 @@ fasttrap_return_common(struct reg *rp, uintptr_t pc, pid_t pid,
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pc - id->fti_probe->ftp_faddr,
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rp->fixreg[3], rp->fixreg[4], 0, 0);
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}
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rm_runlock(&fasttrap_tp_lock, &tracker);
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}
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@ -351,6 +356,7 @@ fasttrap_branch_taken(int bo, int bi, struct reg *regs)
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int
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fasttrap_pid_probe(struct reg *rp)
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{
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struct rm_priotracker tracker;
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proc_t *p = curproc;
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uintptr_t pc = rp->pc;
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uintptr_t new_pc = 0;
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@ -381,8 +387,7 @@ fasttrap_pid_probe(struct reg *rp)
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curthread->t_dtrace_scrpc = 0;
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curthread->t_dtrace_astpc = 0;
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PROC_LOCK(p);
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rm_rlock(&fasttrap_tp_lock, &tracker);
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pid = p->p_pid;
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bucket = &fasttrap_tpoints.fth_table[FASTTRAP_TPOINTS_INDEX(pid, pc)];
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@ -401,7 +406,7 @@ fasttrap_pid_probe(struct reg *rp)
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* fasttrap_ioctl), or somehow we have mislaid this tracepoint.
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*/
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if (tp == NULL) {
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PROC_UNLOCK(p);
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rm_runlock(&fasttrap_tp_lock, &tracker);
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return (-1);
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}
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@ -455,7 +460,7 @@ fasttrap_pid_probe(struct reg *rp)
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* tracepoint again later if we need to light up any return probes.
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*/
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tp_local = *tp;
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PROC_UNLOCK(p);
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rm_runlock(&fasttrap_tp_lock, &tracker);
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tp = &tp_local;
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/*
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